Merge branch 'for-mingo' of...

Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU and LKMM commits from Paul E. McKenney:

 - An LKMM commit adding support for synchronize_srcu_expedited()
 - A couple of straggling RCU flavor consolidation updates
 - Documentation updates.
 - Miscellaneous fixes
 - SRCU updates
 - RCU CPU stall-warning updates
 - Torture-test updates
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/RCU/Design/Data-Structures/Data-Structures.html

@@ -155,8 +155,7 @@ keeping lock contention under control at all tree levels regardless
 of the level of loading on the system.
 
 </p><p>RCU updaters wait for normal grace periods by registering
-RCU callbacks, either directly via <tt>call_rcu()</tt> and
-friends (namely <tt>call_rcu_bh()</tt> and <tt>call_rcu_sched()</tt>),
+RCU callbacks, either directly via <tt>call_rcu()</tt>
 or indirectly via <tt>synchronize_rcu()</tt> and friends.
 RCU callbacks are represented by <tt>rcu_head</tt> structures,
 which are queued on <tt>rcu_data</tt> structures while they are

Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html

@@ -56,6 +56,7 @@ sections.
 RCU-preempt Expedited Grace Periods</a></h2>
 
 <p>
+<tt>CONFIG_PREEMPT=y</tt> kernels implement RCU-preempt.
 The overall flow of the handling of a given CPU by an RCU-preempt
 expedited grace period is shown in the following diagram:
 
@@ -139,6 +140,7 @@ or offline, among other things.
 RCU-sched Expedited Grace Periods</a></h2>
 
 <p>
+<tt>CONFIG_PREEMPT=n</tt> kernels implement RCU-sched.
 The overall flow of the handling of a given CPU by an RCU-sched
 expedited grace period is shown in the following diagram:
 
@@ -146,7 +148,7 @@ expedited grace period is shown in the following diagram:
 
 <p>
 As with RCU-preempt, RCU-sched's
-<tt>synchronize_sched_expedited()</tt> ignores offline and
+<tt>synchronize_rcu_expedited()</tt> ignores offline and
 idle CPUs, again because they are in remotely detectable
 quiescent states.
 However, because the

Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html

@@ -34,12 +34,11 @@ Similarly, any code that happens before the beginning of a given RCU grace
 period is guaranteed to see the effects of all accesses following the end
 of that grace period that are within RCU read-side critical sections.
 
-<p>This guarantee is particularly pervasive for <tt>synchronize_sched()</tt>,
-for which RCU-sched read-side critical sections include any region
+<p>Note well that RCU-sched read-side critical sections include any region
 of code for which preemption is disabled.
 Given that each individual machine instruction can be thought of as
 an extremely small region of preemption-disabled code, one can think of
-<tt>synchronize_sched()</tt> as <tt>smp_mb()</tt> on steroids.
+<tt>synchronize_rcu()</tt> as <tt>smp_mb()</tt> on steroids.
 
 <p>RCU updaters use this guarantee by splitting their updates into
 two phases, one of which is executed before the grace period and

Documentation/RCU/NMI-RCU.txt

@@ -81,18 +81,19 @@ currently executing on some other CPU.  We therefore cannot free
 up any data structures used by the old NMI handler until execution
 of it completes on all other CPUs.
 
-One way to accomplish this is via synchronize_sched(), perhaps as
+One way to accomplish this is via synchronize_rcu(), perhaps as
 follows:
 
 	unset_nmi_callback();
-	synchronize_sched();
+	synchronize_rcu();
 	kfree(my_nmi_data);
 
-This works because synchronize_sched() blocks until all CPUs complete
-any preemption-disabled segments of code that they were executing.
-Since NMI handlers disable preemption, synchronize_sched() is guaranteed
+This works because (as of v4.20) synchronize_rcu() blocks until all
+CPUs complete any preemption-disabled segments of code that they were
+executing.
+Since NMI handlers disable preemption, synchronize_rcu() is guaranteed
 not to return until all ongoing NMI handlers exit.  It is therefore safe
-to free up the handler's data as soon as synchronize_sched() returns.
+to free up the handler's data as soon as synchronize_rcu() returns.
 
 Important note: for this to work, the architecture in question must
 invoke nmi_enter() and nmi_exit() on NMI entry and exit, respectively.

Documentation/RCU/UP.txt

@@ -86,10 +86,8 @@ even on a UP system.  So do not do it!  Even on a UP system, the RCU
 infrastructure -must- respect grace periods, and -must- invoke callbacks
 from a known environment in which no locks are held.
 
-It -is- safe for synchronize_sched() and synchronize_rcu_bh() to return
-immediately on an UP system.  It is also safe for synchronize_rcu()
-to return immediately on UP systems, except when running preemptable
-RCU.
+Note that it -is- safe for synchronize_rcu() to return immediately on
+UP systems, including !PREEMPT SMP builds running on UP systems.
 
 Quick Quiz #3: Why can't synchronize_rcu() return immediately on
 	UP systems running preemptable RCU?

Documentation/RCU/checklist.txt

@@ -182,16 +182,13 @@ over a rather long period of time, but improvements are always welcome!
 		when publicizing a pointer to a structure that can
 		be traversed by an RCU read-side critical section.
 
-5.	If call_rcu(), or a related primitive such as call_rcu_bh(),
-	call_rcu_sched(), or call_srcu() is used, the callback function
-	will be called from softirq context.  In particular, it cannot
-	block.
+5.	If call_rcu() or call_srcu() is used, the callback function will
+	be called from softirq context.  In particular, it cannot block.
 
-6.	Since synchronize_rcu() can block, it cannot be called from
-	any sort of irq context.  The same rule applies for
-	synchronize_rcu_bh(), synchronize_sched(), synchronize_srcu(),
-	synchronize_rcu_expedited(), synchronize_rcu_bh_expedited(),
-	synchronize_sched_expedite(), and synchronize_srcu_expedited().
+6.	Since synchronize_rcu() can block, it cannot be called
+	from any sort of irq context.  The same rule applies
+	for synchronize_srcu(), synchronize_rcu_expedited(), and
+	synchronize_srcu_expedited().
 
 	The expedited forms of these primitives have the same semantics
 	as the non-expedited forms, but expediting is both expensive and
@@ -212,20 +209,20 @@ over a rather long period of time, but improvements are always welcome!
 	of the system, especially to real-time workloads running on
 	the rest of the system.
 
-7.	If the updater uses call_rcu() or synchronize_rcu(), then the
-	corresponding readers must use rcu_read_lock() and
-	rcu_read_unlock().  If the updater uses call_rcu_bh() or
-	synchronize_rcu_bh(), then the corresponding readers must
-	use rcu_read_lock_bh() and rcu_read_unlock_bh().  If the
-	updater uses call_rcu_sched() or synchronize_sched(), then
-	the corresponding readers must disable preemption, possibly
-	by calling rcu_read_lock_sched() and rcu_read_unlock_sched().
-	If the updater uses synchronize_srcu() or call_srcu(), then
-	the corresponding readers must use srcu_read_lock() and
+7.	As of v4.20, a given kernel implements only one RCU flavor,
+	which is RCU-sched for PREEMPT=n and RCU-preempt for PREEMPT=y.
+	If the updater uses call_rcu() or synchronize_rcu(),
+	then the corresponding readers my use rcu_read_lock() and
+	rcu_read_unlock(), rcu_read_lock_bh() and rcu_read_unlock_bh(),
+	or any pair of primitives that disables and re-enables preemption,
+	for example, rcu_read_lock_sched() and rcu_read_unlock_sched().
+	If the updater uses synchronize_srcu() or call_srcu(),
+	then the corresponding readers must use srcu_read_lock() and
 	srcu_read_unlock(), and with the same srcu_struct.  The rules for
 	the expedited primitives are the same as for their non-expedited
 	counterparts.  Mixing things up will result in confusion and
-	broken kernels.
+	broken kernels, and has even resulted in an exploitable security
+	issue.
 
 	One exception to this rule: rcu_read_lock() and rcu_read_unlock()
 	may be substituted for rcu_read_lock_bh() and rcu_read_unlock_bh()
@@ -288,8 +285,7 @@ over a rather long period of time, but improvements are always welcome!
 	d.	Periodically invoke synchronize_rcu(), permitting a limited
 		number of updates per grace period.
 
-	The same cautions apply to call_rcu_bh(), call_rcu_sched(),
-	call_srcu(), and kfree_rcu().
+	The same cautions apply to call_srcu() and kfree_rcu().
 
 	Note that although these primitives do take action to avoid memory
 	exhaustion when any given CPU has too many callbacks, a determined
@@ -322,7 +318,7 @@ over a rather long period of time, but improvements are always welcome!
 
 11.	Any lock acquired by an RCU callback must be acquired elsewhere
 	with softirq disabled, e.g., via spin_lock_irqsave(),
-	spin_lock_bh(), etc.  Failing to disable irq on a given
+	spin_lock_bh(), etc.  Failing to disable softirq on a given
 	acquisition of that lock will result in deadlock as soon as
 	the RCU softirq handler happens to run your RCU callback while
 	interrupting that acquisition's critical section.
@@ -335,13 +331,16 @@ over a rather long period of time, but improvements are always welcome!
 	must use whatever locking or other synchronization is required
 	to safely access and/or modify that data structure.
 
-	RCU callbacks are -usually- executed on the same CPU that executed
-	the corresponding call_rcu(), call_rcu_bh(), or call_rcu_sched(),
-	but are by -no- means guaranteed to be.  For example, if a given
-	CPU goes offline while having an RCU callback pending, then that
-	RCU callback will execute on some surviving CPU.  (If this was
-	not the case, a self-spawning RCU callback would prevent the
-	victim CPU from ever going offline.)
+	Do not assume that RCU callbacks will be executed on the same
+	CPU that executed the corresponding call_rcu() or call_srcu().
+	For example, if a given CPU goes offline while having an RCU
+	callback pending, then that RCU callback will execute on some
+	surviving CPU.	(If this was not the case, a self-spawning RCU
+	callback would prevent the victim CPU from ever going offline.)
+	Furthermore, CPUs designated by rcu_nocbs= might well -always-
+	have their RCU callbacks executed on some other CPUs, in fact,
+	for some  real-time workloads, this is the whole point of using
+	the rcu_nocbs= kernel boot parameter.
 
 13.	Unlike other forms of RCU, it -is- permissible to block in an
 	SRCU read-side critical section (demarked by srcu_read_lock()
@@ -381,11 +380,11 @@ over a rather long period of time, but improvements are always welcome!
 
 	SRCU's expedited primitive (synchronize_srcu_expedited())
 	never sends IPIs to other CPUs, so it is easier on
-	real-time workloads than is synchronize_rcu_expedited(),
-	synchronize_rcu_bh_expedited() or synchronize_sched_expedited().
+	real-time workloads than is synchronize_rcu_expedited().
 
-	Note that rcu_dereference() and rcu_assign_pointer() relate to
-	SRCU just as they do to other forms of RCU.
+	Note that rcu_assign_pointer() relates to SRCU just as it does to
+	other forms of RCU, but instead of rcu_dereference() you should
+	use srcu_dereference() in order to avoid lockdep splats.
 
 14.	The whole point of call_rcu(), synchronize_rcu(), and friends
 	is to wait until all pre-existing readers have finished before
@@ -405,6 +404,9 @@ over a rather long period of time, but improvements are always welcome!
 	read-side critical sections.  It is the responsibility of the
 	RCU update-side primitives to deal with this.
 
+	For SRCU readers, you can use smp_mb__after_srcu_read_unlock()
+	immediately after an srcu_read_unlock() to get a full barrier.
+
 16.	Use CONFIG_PROVE_LOCKING, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and the
 	__rcu sparse checks to validate your RCU code.	These can help
 	find problems as follows:
@@ -428,22 +430,19 @@ over a rather long period of time, but improvements are always welcome!
 	These debugging aids can help you find problems that are
 	otherwise extremely difficult to spot.
 
-17.	If you register a callback using call_rcu(), call_rcu_bh(),
-	call_rcu_sched(), or call_srcu(), and pass in a function defined
-	within a loadable module, then it in necessary to wait for
-	all pending callbacks to be invoked after the last invocation
-	and before unloading that module.  Note that it is absolutely
-	-not- sufficient to wait for a grace period!  The current (say)
-	synchronize_rcu() implementation waits only for all previous
-	callbacks registered on the CPU that synchronize_rcu() is running
-	on, but it is -not- guaranteed to wait for callbacks registered
-	on other CPUs.
+17.	If you register a callback using call_rcu() or call_srcu(), and
+	pass in a function defined within a loadable module, then it in
+	necessary to wait for all pending callbacks to be invoked after
+	the last invocation and before unloading that module.  Note that
+	it is absolutely -not- sufficient to wait for a grace period!
+	The current (say) synchronize_rcu() implementation is -not-
+	guaranteed to wait for callbacks registered on other CPUs.
+	Or even on the current CPU if that CPU recently went offline
+	and came back online.
 
 	You instead need to use one of the barrier functions:
 
 	o	call_rcu() -> rcu_barrier()
-	o	call_rcu_bh() -> rcu_barrier()
-	o	call_rcu_sched() -> rcu_barrier()
 	o	call_srcu() -> srcu_barrier()
 
 	However, these barrier functions are absolutely -not- guaranteed

Documentation/RCU/rcu.txt

@@ -52,10 +52,10 @@ o	If I am running on a uniprocessor kernel, which can only do one
 o	How can I see where RCU is currently used in the Linux kernel?
 
 	Search for "rcu_read_lock", "rcu_read_unlock", "call_rcu",
-	"rcu_read_lock_bh", "rcu_read_unlock_bh", "call_rcu_bh",
-	"srcu_read_lock", "srcu_read_unlock", "synchronize_rcu",
-	"synchronize_net", "synchronize_srcu", and the other RCU
-	primitives.  Or grab one of the cscope databases from:
+	"rcu_read_lock_bh", "rcu_read_unlock_bh", "srcu_read_lock",
+	"srcu_read_unlock", "synchronize_rcu", "synchronize_net",
+	"synchronize_srcu", and the other RCU primitives.  Or grab one
+	of the cscope databases from:
 
 	http://www.rdrop.com/users/paulmck/RCU/linuxusage/rculocktab.html
 

Documentation/RCU/rcu_dereference.txt

@@ -351,3 +351,106 @@ garbage values.
 
 In short, rcu_dereference() is -not- optional when you are going to
 dereference the resulting pointer.
+
+
+WHICH MEMBER OF THE rcu_dereference() FAMILY SHOULD YOU USE?
+
+First, please avoid using rcu_dereference_raw() and also please avoid
+using rcu_dereference_check() and rcu_dereference_protected() with a
+second argument with a constant value of 1 (or true, for that matter).
+With that caution out of the way, here is some guidance for which
+member of the rcu_dereference() to use in various situations:
+
+1.	If the access needs to be within an RCU read-side critical
+	section, use rcu_dereference().  With the new consolidated
+	RCU flavors, an RCU read-side critical section is entered
+	using rcu_read_lock(), anything that disables bottom halves,
+	anything that disables interrupts, or anything that disables
+	preemption.
+
+2.	If the access might be within an RCU read-side critical section
+	on the one hand, or protected by (say) my_lock on the other,
+	use rcu_dereference_check(), for example:
+
+		p1 = rcu_dereference_check(p->rcu_protected_pointer,
+					   lockdep_is_held(&my_lock));
+
+
+3.	If the access might be within an RCU read-side critical section
+	on the one hand, or protected by either my_lock or your_lock on
+	the other, again use rcu_dereference_check(), for example:
+
+		p1 = rcu_dereference_check(p->rcu_protected_pointer,
+					   lockdep_is_held(&my_lock) ||
+					   lockdep_is_held(&your_lock));
+
+4.	If the access is on the update side, so that it is always protected
+	by my_lock, use rcu_dereference_protected():
+
+		p1 = rcu_dereference_protected(p->rcu_protected_pointer,
+					       lockdep_is_held(&my_lock));
+
+	This can be extended to handle multiple locks as in #3 above,
+	and both can be extended to check other conditions as well.
+
+5.	If the protection is supplied by the caller, and is thus unknown
+	to this code, that is the rare case when rcu_dereference_raw()
+	is appropriate.  In addition, rcu_dereference_raw() might be
+	appropriate when the lockdep expression would be excessively
+	complex, except that a better approach in that case might be to
+	take a long hard look at your synchronization design.  Still,
+	there are data-locking cases where any one of a very large number
+	of locks or reference counters suffices to protect the pointer,
+	so rcu_dereference_raw() does have its place.
+
+	However, its place is probably quite a bit smaller than one
+	might expect given the number of uses in the current kernel.
+	Ditto for its synonym, rcu_dereference_check( ... , 1), and
+	its close relative, rcu_dereference_protected(... , 1).
+
+
+SPARSE CHECKING OF RCU-PROTECTED POINTERS
+
+The sparse static-analysis tool checks for direct access to RCU-protected
+pointers, which can result in "interesting" bugs due to compiler
+optimizations involving invented loads and perhaps also load tearing.
+For example, suppose someone mistakenly does something like this:
+
+	p = q->rcu_protected_pointer;
+	do_something_with(p->a);
+	do_something_else_with(p->b);
+
+If register pressure is high, the compiler might optimize "p" out
+of existence, transforming the code to something like this:
+
+	do_something_with(q->rcu_protected_pointer->a);
+	do_something_else_with(q->rcu_protected_pointer->b);
+
+This could fatally disappoint your code if q->rcu_protected_pointer
+changed in the meantime.  Nor is this a theoretical problem:  Exactly
+this sort of bug cost Paul E. McKenney (and several of his innocent
+colleagues) a three-day weekend back in the early 1990s.
+
+Load tearing could of course result in dereferencing a mashup of a pair
+of pointers, which also might fatally disappoint your code.
+
+These problems could have been avoided simply by making the code instead
+read as follows:
+
+	p = rcu_dereference(q->rcu_protected_pointer);
+	do_something_with(p->a);
+	do_something_else_with(p->b);
+
+Unfortunately, these sorts of bugs can be extremely hard to spot during
+review.  This is where the sparse tool comes into play, along with the
+"__rcu" marker.  If you mark a pointer declaration, whether in a structure
+or as a formal parameter, with "__rcu", which tells sparse to complain if
+this pointer is accessed directly.  It will also cause sparse to complain
+if a pointer not marked with "__rcu" is accessed using rcu_dereference()
+and friends.  For example, ->rcu_protected_pointer might be declared as
+follows:
+
+	struct foo __rcu *rcu_protected_pointer;
+
+Use of "__rcu" is opt-in.  If you choose not to use it, then you should
+ignore the sparse warnings.

Documentation/RCU/rcubarrier.txt

@@ -83,16 +83,15 @@ Pseudo-code using rcu_barrier() is as follows:
    2. Execute rcu_barrier().
    3. Allow the module to be unloaded.
 
-There are also rcu_barrier_bh(), rcu_barrier_sched(), and srcu_barrier()
-functions for the other flavors of RCU, and you of course must match
-the flavor of rcu_barrier() with that of call_rcu().  If your module
-uses multiple flavors of call_rcu(), then it must also use multiple
+There is also an srcu_barrier() function for SRCU, and you of course
+must match the flavor of rcu_barrier() with that of call_rcu().  If your
+module uses multiple flavors of call_rcu(), then it must also use multiple
 flavors of rcu_barrier() when unloading that module.  For example, if
-it uses call_rcu_bh(), call_srcu() on srcu_struct_1, and call_srcu() on
+it uses call_rcu(), call_srcu() on srcu_struct_1, and call_srcu() on
 srcu_struct_2(), then the following three lines of code will be required
 when unloading:
 
- 1 rcu_barrier_bh();
+ 1 rcu_barrier();
  2 srcu_barrier(&srcu_struct_1);
  3 srcu_barrier(&srcu_struct_2);
 
@@ -185,12 +184,12 @@ module invokes call_rcu() from timers, you will need to first cancel all
 the timers, and only then invoke rcu_barrier() to wait for any remaining
 RCU callbacks to complete.
 
-Of course, if you module uses call_rcu_bh(), you will need to invoke
-rcu_barrier_bh() before unloading.  Similarly, if your module uses
-call_rcu_sched(), you will need to invoke rcu_barrier_sched() before
-unloading.  If your module uses call_rcu(), call_rcu_bh(), -and-
-call_rcu_sched(), then you will need to invoke each of rcu_barrier(),
-rcu_barrier_bh(), and rcu_barrier_sched().
+Of course, if you module uses call_rcu(), you will need to invoke
+rcu_barrier() before unloading.  Similarly, if your module uses
+call_srcu(), you will need to invoke srcu_barrier() before unloading,
+and on the same srcu_struct structure.  If your module uses call_rcu()
+-and- call_srcu(), then you will need to invoke rcu_barrier() -and-
+srcu_barrier().
 
 
 Implementing rcu_barrier()
@@ -223,8 +222,8 @@ shown below. Note that the final "1" in on_each_cpu()'s argument list
 ensures that all the calls to rcu_barrier_func() will have completed
 before on_each_cpu() returns. Line 9 then waits for the completion.
 
-This code was rewritten in 2008 to support rcu_barrier_bh() and
-rcu_barrier_sched() in addition to the original rcu_barrier().
+This code was rewritten in 2008 and several times thereafter, but this
+still gives the general idea.
 
 The rcu_barrier_func() runs on each CPU, where it invokes call_rcu()
 to post an RCU callback, as follows:

Documentation/RCU/whatisRCU.txt

@@ -310,7 +310,7 @@ reader, updater, and reclaimer.
 
 
 	    rcu_assign_pointer()
-	    			    +--------+
+	                            +--------+
 	    +---------------------->| reader |---------+
 	    |                       +--------+         |
 	    |                           |              |
@@ -318,12 +318,12 @@ reader, updater, and reclaimer.
 	    |                           |              | rcu_read_lock()
 	    |                           |              | rcu_read_unlock()
 	    |        rcu_dereference()  |              |
-       +---------+                      |              |
-       | updater |<---------------------+              |
-       +---------+                                     V
+	    +---------+                 |              |
+	    | updater |<----------------+              |
+	    +---------+                                V
 	    |                                    +-----------+
 	    +----------------------------------->| reclaimer |
-	    				         +-----------+
+	                                         +-----------+
 	      Defer:
 	      synchronize_rcu() & call_rcu()
 

Documentation/admin-guide/kernel-parameters.txt

@@ -3623,7 +3623,9 @@
 				see CONFIG_RAS_CEC help text.
 
 	rcu_nocbs=	[KNL]
-			The argument is a cpu list, as described above.
+			The argument is a cpu list, as described above,
+			except that the string "all" can be used to
+			specify every CPU on the system.
 
 			In kernels built with CONFIG_RCU_NOCB_CPU=y, set
 			the specified list of CPUs to be no-callback CPUs.

Documentation/atomic_t.txt

@@ -56,6 +56,23 @@ Barriers:
   smp_mb__{before,after}_atomic()
 
 
+TYPES (signed vs unsigned)
+-----
+
+While atomic_t, atomic_long_t and atomic64_t use int, long and s64
+respectively (for hysterical raisins), the kernel uses -fno-strict-overflow
+(which implies -fwrapv) and defines signed overflow to behave like
+2s-complement.
+
+Therefore, an explicitly unsigned variant of the atomic ops is strictly
+unnecessary and we can simply cast, there is no UB.
+
+There was a bug in UBSAN prior to GCC-8 that would generate UB warnings for
+signed types.
+
+With this we also conform to the C/C++ _Atomic behaviour and things like
+P1236R1.
+
 
 SEMANTICS
 ---------

Documentation/kprobes.txt

@@ -243,10 +243,10 @@ Optimization
 ^^^^^^^^^^^^
 
 The Kprobe-optimizer doesn't insert the jump instruction immediately;
-rather, it calls synchronize_sched() for safety first, because it's
+rather, it calls synchronize_rcu() for safety first, because it's
 possible for a CPU to be interrupted in the middle of executing the
-optimized region [3]_.  As you know, synchronize_sched() can ensure
-that all interruptions that were active when synchronize_sched()
+optimized region [3]_.  As you know, synchronize_rcu() can ensure
+that all interruptions that were active when synchronize_rcu()
 was called are done, but only if CONFIG_PREEMPT=n.  So, this version
 of kprobe optimization supports only kernels with CONFIG_PREEMPT=n [4]_.
 

Documentation/translations/ko_KR/memory-barriers.txt

@@ -493,10 +493,8 @@ CPU 에게 기대할 수 있는 최소한의 보장사항 몇가지가 있습니
      이 타입의 오퍼레이션은 단방향의 투과성 배리어처럼 동작합니다.  ACQUIRE
      오퍼레이션 뒤의 모든 메모리 오퍼레이션들이 ACQUIRE 오퍼레이션 후에
      일어난 것으로 시스템의 나머지 컴포넌트들에 보이게 될 것이 보장됩니다.
-     LOCK 오퍼레이션과 smp_load_acquire(), smp_cond_acquire() 오퍼레이션도
-     ACQUIRE 오퍼레이션에 포함됩니다.  smp_cond_acquire() 오퍼레이션은 컨트롤
-     의존성과 smp_rmb() 를 사용해서 ACQUIRE 의 의미적 요구사항(semantic)을
-     충족시킵니다.
+     LOCK 오퍼레이션과 smp_load_acquire(), smp_cond_load_acquire() 오퍼레이션도
+     ACQUIRE 오퍼레이션에 포함됩니다.
 
      ACQUIRE 오퍼레이션 앞의 메모리 오퍼레이션들은 ACQUIRE 오퍼레이션 완료 후에
      수행된 것처럼 보일 수 있습니다.
@@ -2146,33 +2144,40 @@ set_current_state() 는 다음의 것들로 감싸질 수도 있습니다:
 	event_indicated = 1;
 	wake_up_process(event_daemon);
 
-wake_up() 류에 의해 쓰기 메모리 배리어가 내포됩니다.  만약 그것들이 뭔가를
-깨운다면요.  이 배리어는 태스크 상태가 지워지기 전에 수행되므로, 이벤트를
-알리기 위한 STORE 와 태스크 상태를 TASK_RUNNING 으로 설정하는 STORE 사이에
-위치하게 됩니다.
+wake_up() 이 무언가를 깨우게 되면, 이 함수는 범용 메모리 배리어를 수행합니다.
+이 함수가 아무것도 깨우지 않는다면 메모리 배리어는 수행될 수도, 수행되지 않을
+수도 있습니다; 이 경우에 메모리 배리어를 수행할 거라 오해해선 안됩니다.  이
+배리어는 태스크 상태가 접근되기 전에 수행되는데, 자세히 말하면 이 이벤트를
+알리기 위한 STORE 와 TASK_RUNNING 으로 상태를 쓰는 STORE 사이에 수행됩니다:
 
-	CPU 1				CPU 2
+	CPU 1 (Sleeper)			CPU 2 (Waker)
 	===============================	===============================
 	set_current_state();		STORE event_indicated
 	  smp_store_mb();		wake_up();
-	    STORE current->state	  <쓰기 배리어>
-	    <범용 배리어>		  STORE current->state
-	LOAD event_indicated
+	    STORE current->state	  ...
+	    <범용 배리어>		  <범용 배리어>
+	LOAD event_indicated		  if ((LOAD task->state) & TASK_NORMAL)
+					    STORE task->state
 
-한번더 말합니다만, 이 쓰기 메모리 배리어는 이 코드가 정말로 뭔가를 깨울 때에만
-실행됩니다.  이걸 설명하기 위해, X 와 Y 는 모두 0 으로 초기화 되어 있다는 가정
-하에 아래의 이벤트 시퀀스를 생각해 봅시다:
+여기서 "task" 는 깨어나지는 쓰레드이고 CPU 1 의 "current" 와 같습니다.
+
+반복하지만, wake_up() 이 무언가를 정말 깨운다면 범용 메모리 배리어가 수행될
+것이 보장되지만, 그렇지 않다면 그런 보장이 없습니다.  이걸 이해하기 위해, X 와
+Y 는 모두 0 으로 초기화 되어 있다는 가정 하에 아래의 이벤트 시퀀스를 생각해
+봅시다:
 
 	CPU 1				CPU 2
 	===============================	===============================
-	X = 1;				STORE event_indicated
+	X = 1;				Y = 1;
 	smp_mb();			wake_up();
-	Y = 1;				wait_event(wq, Y == 1);
-	wake_up();			  load from Y sees 1, no memory barrier
-					load from X might see 0
+	LOAD Y				LOAD X
+
+정말로 깨우기가 행해졌다면, 두 로드 중 (최소한) 하나는 1 을 보게 됩니다.
+반면에, 실제 깨우기가 행해지지 않았다면, 두 로드 모두 0을 볼 수도 있습니다.
 
-위 예제에서의 경우와 달리 깨우기가 정말로 행해졌다면, CPU 2 의 X 로드는 1 을
-본다고 보장될 수 있을 겁니다.
+wake_up_process() 는 항상 범용 메모리 배리어를 수행합니다.  이 배리어 역시
+태스크 상태가 접근되기 전에 수행됩니다.  특히, 앞의 예제 코드에서 wake_up() 이
+wake_up_process() 로 대체된다면 두 로드 중 하나는 1을 볼 것이 보장됩니다.
 
 사용 가능한 깨우기류 함수들로 다음과 같은 것들이 있습니다:
 
@@ -2192,6 +2197,8 @@ wake_up() 류에 의해 쓰기 메모리 배리어가 내포됩니다.  만약
 	wake_up_poll();
 	wake_up_process();
 
+메모리 순서규칙 관점에서, 이 함수들은 모두 wake_up() 과 같거나 보다 강한 순서
+보장을 제공합니다.
 
 [!] 잠재우는 코드와 깨우는 코드에 내포되는 메모리 배리어들은 깨우기 전에
 이루어진 스토어를 잠재우는 코드가 set_current_state() 를 호출한 후에 행하는

MAINTAINERS

@@ -8993,7 +8993,7 @@ R:	Daniel Lustig <dlustig@nvidia.com>
 L:	linux-kernel@vger.kernel.org
 L:	linux-arch@vger.kernel.org
 S:	Supported
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
 F:	tools/memory-model/
 F:	Documentation/atomic_bitops.txt
 F:	Documentation/atomic_t.txt
@@ -13041,9 +13041,9 @@ M:	Josh Triplett <josh@joshtriplett.org>
 R:	Steven Rostedt <rostedt@goodmis.org>
 R:	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 R:	Lai Jiangshan <jiangshanlai@gmail.com>
-L:	linux-kernel@vger.kernel.org
+L:	rcu@vger.kernel.org
 S:	Supported
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
 F:	tools/testing/selftests/rcutorture
 
 RDC R-321X SoC
@@ -13089,10 +13089,10 @@ R:	Steven Rostedt <rostedt@goodmis.org>
 R:	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 R:	Lai Jiangshan <jiangshanlai@gmail.com>
 R:	Joel Fernandes <joel@joelfernandes.org>
-L:	linux-kernel@vger.kernel.org
+L:	rcu@vger.kernel.org
 W:	http://www.rdrop.com/users/paulmck/RCU/
 S:	Supported
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
 F:	Documentation/RCU/
 X:	Documentation/RCU/torture.txt
 F:	include/linux/rcu*
@@ -14244,10 +14244,10 @@ M:	"Paul E. McKenney" <paulmck@linux.ibm.com>
 M:	Josh Triplett <josh@joshtriplett.org>
 R:	Steven Rostedt <rostedt@goodmis.org>
 R:	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
-L:	linux-kernel@vger.kernel.org
+L:	rcu@vger.kernel.org
 W:	http://www.rdrop.com/users/paulmck/RCU/
 S:	Supported
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
 F:	include/linux/srcu*.h
 F:	kernel/rcu/srcu*.c
 
@@ -15694,7 +15694,7 @@ M:	"Paul E. McKenney" <paulmck@linux.ibm.com>
 M:	Josh Triplett <josh@joshtriplett.org>
 L:	linux-kernel@vger.kernel.org
 S:	Supported
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
 F:	Documentation/RCU/torture.txt
 F:	kernel/torture.c
 F:	kernel/rcu/rcutorture.c

drivers/nvme/host/core.c

@@ -388,7 +388,7 @@ static void nvme_free_ns_head(struct kref *ref)
 	nvme_mpath_remove_disk(head);
 	ida_simple_remove(&head->subsys->ns_ida, head->instance);
 	list_del_init(&head->entry);
-	cleanup_srcu_struct_quiesced(&head->srcu);
+	cleanup_srcu_struct(&head->srcu);
 	nvme_put_subsystem(head->subsys);
 	kfree(head);
 }

include/linux/rcupdate.h

@@ -878,9 +878,11 @@ static inline void rcu_head_init(struct rcu_head *rhp)
 static inline bool
 rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f)
 {
-	if (READ_ONCE(rhp->func) == f)
+	rcu_callback_t func = READ_ONCE(rhp->func);
+
+	if (func == f)
 		return true;
-	WARN_ON_ONCE(READ_ONCE(rhp->func) != (rcu_callback_t)~0L);
+	WARN_ON_ONCE(func != (rcu_callback_t)~0L);
 	return false;
 }
 

include/linux/srcu.h

@@ -56,45 +56,11 @@ struct srcu_struct { };
 
 void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
 		void (*func)(struct rcu_head *head));
-void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced);
+void cleanup_srcu_struct(struct srcu_struct *ssp);
 int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
 void synchronize_srcu(struct srcu_struct *ssp);
 
-/**
- * cleanup_srcu_struct - deconstruct a sleep-RCU structure
- * @ssp: structure to clean up.
- *
- * Must invoke this after you are finished using a given srcu_struct that
- * was initialized via init_srcu_struct(), else you leak memory.
- */
-static inline void cleanup_srcu_struct(struct srcu_struct *ssp)
-{
-	_cleanup_srcu_struct(ssp, false);
-}
-
-/**
- * cleanup_srcu_struct_quiesced - deconstruct a quiesced sleep-RCU structure
- * @ssp: structure to clean up.
- *
- * Must invoke this after you are finished using a given srcu_struct that
- * was initialized via init_srcu_struct(), else you leak memory.  Also,
- * all grace-period processing must have completed.
- *
- * "Completed" means that the last synchronize_srcu() and
- * synchronize_srcu_expedited() calls must have returned before the call
- * to cleanup_srcu_struct_quiesced().  It also means that the callback
- * from the last call_srcu() must have been invoked before the call to
- * cleanup_srcu_struct_quiesced(), but you can use srcu_barrier() to help
- * with this last.  Violating these rules will get you a WARN_ON() splat
- * (with high probability, anyway), and will also cause the srcu_struct
- * to be leaked.
- */
-static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *ssp)
-{
-	_cleanup_srcu_struct(ssp, true);
-}
-
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
 /**

kernel/locking/locktorture.c

@@ -829,7 +829,9 @@ static void lock_torture_cleanup(void)
 						"End of test: SUCCESS");
 
 	kfree(cxt.lwsa);
+	cxt.lwsa = NULL;
 	kfree(cxt.lrsa);
+	cxt.lrsa = NULL;
 
 end:
 	torture_cleanup_end();

kernel/rcu/rcu.h

@@ -233,6 +233,7 @@ static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 #ifdef CONFIG_RCU_STALL_COMMON
 
 extern int rcu_cpu_stall_suppress;
+extern int rcu_cpu_stall_timeout;
 int rcu_jiffies_till_stall_check(void);
 
 #define rcu_ftrace_dump_stall_suppress() \

kernel/rcu/rcuperf.c

@@ -494,6 +494,10 @@ rcu_perf_cleanup(void)
 
 	if (torture_cleanup_begin())
 		return;
+	if (!cur_ops) {
+		torture_cleanup_end();
+		return;
+	}
 
 	if (reader_tasks) {
 		for (i = 0; i < nrealreaders; i++)
@@ -614,6 +618,7 @@ rcu_perf_init(void)
 		pr_cont("\n");
 		WARN_ON(!IS_MODULE(CONFIG_RCU_PERF_TEST));
 		firsterr = -EINVAL;
+		cur_ops = NULL;
 		goto unwind;
 	}
 	if (cur_ops->init)

kernel/rcu/rcutorture.c

@@ -299,7 +299,6 @@ struct rcu_torture_ops {
 	int irq_capable;
 	int can_boost;
 	int extendables;
-	int ext_irq_conflict;
 	const char *name;
 };
 
@@ -592,12 +591,7 @@ static void srcu_torture_init(void)
 
 static void srcu_torture_cleanup(void)
 {
-	static DEFINE_TORTURE_RANDOM(rand);
-
-	if (torture_random(&rand) & 0x800)
-		cleanup_srcu_struct(&srcu_ctld);
-	else
-		cleanup_srcu_struct_quiesced(&srcu_ctld);
+	cleanup_srcu_struct(&srcu_ctld);
 	srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
 }
 
@@ -1160,7 +1154,7 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
 	unsigned long randmask2 = randmask1 >> 3;
 
 	WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
-	/* Most of the time lots of bits, half the time only one bit. */
+	/* Mostly only one bit (need preemption!), sometimes lots of bits. */
 	if (!(randmask1 & 0x7))
 		mask = mask & randmask2;
 	else
@@ -1170,10 +1164,6 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
 	    ((!(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) ||
 	     (!(mask & RCUTORTURE_RDR_RBH) && (oldmask & RCUTORTURE_RDR_RBH))))
 		mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
-	if ((mask & RCUTORTURE_RDR_IRQ) &&
-	    !(mask & cur_ops->ext_irq_conflict) &&
-	    (oldmask & cur_ops->ext_irq_conflict))
-		mask |= cur_ops->ext_irq_conflict; /* Or if readers object. */
 	return mask ?: RCUTORTURE_RDR_RCU;
 }
 
@@ -1848,7 +1838,7 @@ static int rcutorture_oom_notify(struct notifier_block *self,
 	WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
 	     __func__);
 	rcu_torture_fwd_cb_hist();
-	rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat) / 2));
+	rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat)) / 2);
 	WRITE_ONCE(rcu_fwd_emergency_stop, true);
 	smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
 	pr_info("%s: Freed %lu RCU callbacks.\n",
@@ -2094,6 +2084,10 @@ rcu_torture_cleanup(void)
 			cur_ops->cb_barrier();
 		return;
 	}
+	if (!cur_ops) {
+		torture_cleanup_end();
+		return;
+	}
 
 	rcu_torture_barrier_cleanup();
 	torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
@@ -2267,6 +2261,7 @@ rcu_torture_init(void)
 		pr_cont("\n");
 		WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
 		firsterr = -EINVAL;
+		cur_ops = NULL;
 		goto unwind;
 	}
 	if (cur_ops->fqs == NULL && fqs_duration != 0) {

kernel/rcu/srcutiny.c

@@ -76,19 +76,16 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
  * Must invoke this after you are finished using a given srcu_struct that
  * was initialized via init_srcu_struct(), else you leak memory.
  */
-void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced)
+void cleanup_srcu_struct(struct srcu_struct *ssp)
 {
 	WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]);
-	if (quiesced)
-		WARN_ON(work_pending(&ssp->srcu_work));
-	else
-		flush_work(&ssp->srcu_work);
+	flush_work(&ssp->srcu_work);
 	WARN_ON(ssp->srcu_gp_running);
 	WARN_ON(ssp->srcu_gp_waiting);
 	WARN_ON(ssp->srcu_cb_head);
 	WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail);
 }
-EXPORT_SYMBOL_GPL(_cleanup_srcu_struct);
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /*
  * Removes the count for the old reader from the appropriate element of

kernel/rcu/srcutree.c

@@ -360,8 +360,14 @@ static unsigned long srcu_get_delay(struct srcu_struct *ssp)
 	return SRCU_INTERVAL;
 }
 
-/* Helper for cleanup_srcu_struct() and cleanup_srcu_struct_quiesced(). */
-void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced)
+/**
+ * cleanup_srcu_struct - deconstruct a sleep-RCU structure
+ * @ssp: structure to clean up.
+ *
+ * Must invoke this after you are finished using a given srcu_struct that
+ * was initialized via init_srcu_struct(), else you leak memory.
+ */
+void cleanup_srcu_struct(struct srcu_struct *ssp)
 {
 	int cpu;
 
@@ -369,24 +375,14 @@ void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced)
 		return; /* Just leak it! */
 	if (WARN_ON(srcu_readers_active(ssp)))
 		return; /* Just leak it! */
-	if (quiesced) {
-		if (WARN_ON(delayed_work_pending(&ssp->work)))
-			return; /* Just leak it! */
-	} else {
-		flush_delayed_work(&ssp->work);
-	}
+	flush_delayed_work(&ssp->work);
 	for_each_possible_cpu(cpu) {
 		struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu);
 
-		if (quiesced) {
-			if (WARN_ON(timer_pending(&sdp->delay_work)))
-				return; /* Just leak it! */
-			if (WARN_ON(work_pending(&sdp->work)))
-				return; /* Just leak it! */
-		} else {
-			del_timer_sync(&sdp->delay_work);
-			flush_work(&sdp->work);
-		}
+		del_timer_sync(&sdp->delay_work);
+		flush_work(&sdp->work);
+		if (WARN_ON(rcu_segcblist_n_cbs(&sdp->srcu_cblist)))
+			return; /* Forgot srcu_barrier(), so just leak it! */
 	}
 	if (WARN_ON(rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
 	    WARN_ON(srcu_readers_active(ssp))) {
@@ -397,7 +393,7 @@ void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced)
 	free_percpu(ssp->sda);
 	ssp->sda = NULL;
 }
-EXPORT_SYMBOL_GPL(_cleanup_srcu_struct);
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /*
  * Counts the new reader in the appropriate per-CPU element of the

kernel/rcu/tiny.c

@@ -52,7 +52,7 @@ void rcu_qs(void)
 	local_irq_save(flags);
 	if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) {
 		rcu_ctrlblk.donetail = rcu_ctrlblk.curtail;
-		raise_softirq(RCU_SOFTIRQ);
+		raise_softirq_irqoff(RCU_SOFTIRQ);
 	}
 	local_irq_restore(flags);
 }

kernel/rcu/tree.h

@@ -393,15 +393,13 @@ static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
 
 int rcu_dynticks_snap(struct rcu_data *rdp);
 
-/* Forward declarations for rcutree_plugin.h */
+/* Forward declarations for tree_plugin.h */
 static void rcu_bootup_announce(void);
 static void rcu_qs(void);
 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 #ifdef CONFIG_HOTPLUG_CPU
 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
-static void rcu_print_detail_task_stall(void);
-static int rcu_print_task_stall(struct rcu_node *rnp);
 static int rcu_print_task_exp_stall(struct rcu_node *rnp);
 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 static void rcu_flavor_sched_clock_irq(int user);
@@ -418,9 +416,6 @@ static void rcu_prepare_for_idle(void);
 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
 static void rcu_preempt_deferred_qs(struct task_struct *t);
-static void print_cpu_stall_info_begin(void);
-static void print_cpu_stall_info(int cpu);
-static void print_cpu_stall_info_end(void);
 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 static bool rcu_nocb_cpu_needs_barrier(int cpu);
 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
@@ -445,3 +440,10 @@ static void rcu_bind_gp_kthread(void);
 static bool rcu_nohz_full_cpu(void);
 static void rcu_dynticks_task_enter(void);
 static void rcu_dynticks_task_exit(void);
+
+/* Forward declarations for tree_stall.h */
+static void record_gp_stall_check_time(void);
+static void rcu_iw_handler(struct irq_work *iwp);
+static void check_cpu_stall(struct rcu_data *rdp);
+static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
+				     const unsigned long gpssdelay);

kernel/rcu/tree_exp.h

@@ -10,6 +10,7 @@
 #include <linux/lockdep.h>
 
 static void rcu_exp_handler(void *unused);
+static int rcu_print_task_exp_stall(struct rcu_node *rnp);
 
 /*
  * Record the start of an expedited grace period.
@@ -633,7 +634,7 @@ static void rcu_exp_handler(void *unused)
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->expmask & rdp->grpmask) {
 			rdp->deferred_qs = true;
-			WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true);
+			t->rcu_read_unlock_special.b.exp_hint = true;
 		}
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 		return;
@@ -648,7 +649,7 @@ static void rcu_exp_handler(void *unused)
 	 *
 	 * If the CPU is fully enabled (or if some buggy RCU-preempt
 	 * read-side critical section is being used from idle), just
-	 * invoke rcu_preempt_defer_qs() to immediately report the
+	 * invoke rcu_preempt_deferred_qs() to immediately report the
 	 * quiescent state.  We cannot use rcu_read_unlock_special()
 	 * because we are in an interrupt handler, which will cause that
 	 * function to take an early exit without doing anything.
@@ -670,6 +671,27 @@ static void sync_sched_exp_online_cleanup(int cpu)
 {
 }
 
+/*
+ * Scan the current list of tasks blocked within RCU read-side critical
+ * sections, printing out the tid of each that is blocking the current
+ * expedited grace period.
+ */
+static int rcu_print_task_exp_stall(struct rcu_node *rnp)
+{
+	struct task_struct *t;
+	int ndetected = 0;
+
+	if (!rnp->exp_tasks)
+		return 0;
+	t = list_entry(rnp->exp_tasks->prev,
+		       struct task_struct, rcu_node_entry);
+	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
+		pr_cont(" P%d", t->pid);
+		ndetected++;
+	}
+	return ndetected;
+}
+
 #else /* #ifdef CONFIG_PREEMPT_RCU */
 
 /* Invoked on each online non-idle CPU for expedited quiescent state. */
@@ -709,6 +731,16 @@ static void sync_sched_exp_online_cleanup(int cpu)
 	WARN_ON_ONCE(ret);
 }
 
+/*
+ * Because preemptible RCU does not exist, we never have to check for
+ * tasks blocked within RCU read-side critical sections that are
+ * blocking the current expedited grace period.
+ */
+static int rcu_print_task_exp_stall(struct rcu_node *rnp)
+{
+	return 0;
+}
+
 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 
 /**

kernel/rcu/tree_plugin.h

@@ -285,7 +285,7 @@ static void rcu_qs(void)
 				       TPS("cpuqs"));
 		__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
 		barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */
-		current->rcu_read_unlock_special.b.need_qs = false;
+		WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false);
 	}
 }
 
@@ -642,100 +642,6 @@ static void rcu_read_unlock_special(struct task_struct *t)
 	rcu_preempt_deferred_qs_irqrestore(t, flags);
 }
 
-/*
- * Dump detailed information for all tasks blocking the current RCU
- * grace period on the specified rcu_node structure.
- */
-static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
-{
-	unsigned long flags;
-	struct task_struct *t;
-
-	raw_spin_lock_irqsave_rcu_node(rnp, flags);
-	if (!rcu_preempt_blocked_readers_cgp(rnp)) {
-		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-		return;
-	}
-	t = list_entry(rnp->gp_tasks->prev,
-		       struct task_struct, rcu_node_entry);
-	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
-		/*
-		 * We could be printing a lot while holding a spinlock.
-		 * Avoid triggering hard lockup.
-		 */
-		touch_nmi_watchdog();
-		sched_show_task(t);
-	}
-	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-}
-
-/*
- * Dump detailed information for all tasks blocking the current RCU
- * grace period.
- */
-static void rcu_print_detail_task_stall(void)
-{
-	struct rcu_node *rnp = rcu_get_root();
-
-	rcu_print_detail_task_stall_rnp(rnp);
-	rcu_for_each_leaf_node(rnp)
-		rcu_print_detail_task_stall_rnp(rnp);
-}
-
-static void rcu_print_task_stall_begin(struct rcu_node *rnp)
-{
-	pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
-	       rnp->level, rnp->grplo, rnp->grphi);
-}
-
-static void rcu_print_task_stall_end(void)
-{
-	pr_cont("\n");
-}
-
-/*
- * Scan the current list of tasks blocked within RCU read-side critical
- * sections, printing out the tid of each.
- */
-static int rcu_print_task_stall(struct rcu_node *rnp)
-{
-	struct task_struct *t;
-	int ndetected = 0;
-
-	if (!rcu_preempt_blocked_readers_cgp(rnp))
-		return 0;
-	rcu_print_task_stall_begin(rnp);
-	t = list_entry(rnp->gp_tasks->prev,
-		       struct task_struct, rcu_node_entry);
-	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
-		pr_cont(" P%d", t->pid);
-		ndetected++;
-	}
-	rcu_print_task_stall_end();
-	return ndetected;
-}
-
-/*
- * Scan the current list of tasks blocked within RCU read-side critical
- * sections, printing out the tid of each that is blocking the current
- * expedited grace period.
- */
-static int rcu_print_task_exp_stall(struct rcu_node *rnp)
-{
-	struct task_struct *t;
-	int ndetected = 0;
-
-	if (!rnp->exp_tasks)
-		return 0;
-	t = list_entry(rnp->exp_tasks->prev,
-		       struct task_struct, rcu_node_entry);
-	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
-		pr_cont(" P%d", t->pid);
-		ndetected++;
-	}
-	return ndetected;
-}
-
 /*
  * Check that the list of blocked tasks for the newly completed grace
  * period is in fact empty.  It is a serious bug to complete a grace
@@ -804,19 +710,25 @@ static void rcu_flavor_sched_clock_irq(int user)
 
 /*
  * Check for a task exiting while in a preemptible-RCU read-side
- * critical section, clean up if so.  No need to issue warnings,
- * as debug_check_no_locks_held() already does this if lockdep
- * is enabled.
+ * critical section, clean up if so.  No need to issue warnings, as
+ * debug_check_no_locks_held() already does this if lockdep is enabled.
+ * Besides, if this function does anything other than just immediately
+ * return, there was a bug of some sort.  Spewing warnings from this
+ * function is like as not to simply obscure important prior warnings.
  */
 void exit_rcu(void)
 {
 	struct task_struct *t = current;
 
-	if (likely(list_empty(&current->rcu_node_entry)))
+	if (unlikely(!list_empty(&current->rcu_node_entry))) {
+		t->rcu_read_lock_nesting = 1;
+		barrier();
+		WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true);
+	} else if (unlikely(t->rcu_read_lock_nesting)) {
+		t->rcu_read_lock_nesting = 1;
+	} else {
 		return;
-	t->rcu_read_lock_nesting = 1;
-	barrier();
-	t->rcu_read_unlock_special.b.blocked = true;
+	}
 	__rcu_read_unlock();
 	rcu_preempt_deferred_qs(current);
 }
@@ -979,33 +891,6 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
 }
 static void rcu_preempt_deferred_qs(struct task_struct *t) { }
 
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * tasks blocked within RCU read-side critical sections.
- */
-static void rcu_print_detail_task_stall(void)
-{
-}
-
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * tasks blocked within RCU read-side critical sections.
- */
-static int rcu_print_task_stall(struct rcu_node *rnp)
-{
-	return 0;
-}
-
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * tasks blocked within RCU read-side critical sections that are
- * blocking the current expedited grace period.
- */
-static int rcu_print_task_exp_stall(struct rcu_node *rnp)
-{
-	return 0;
-}
-
 /*
  * Because there is no preemptible RCU, there can be no readers blocked,
  * so there is no need to check for blocked tasks.  So check only for
@@ -1185,8 +1070,6 @@ static int rcu_boost_kthread(void *arg)
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
 	__releases(rnp->lock)
 {
-	struct task_struct *t;
-
 	raw_lockdep_assert_held_rcu_node(rnp);
 	if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -1200,9 +1083,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
 		if (rnp->exp_tasks == NULL)
 			rnp->boost_tasks = rnp->gp_tasks;
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-		t = rnp->boost_kthread_task;
-		if (t)
-			rcu_wake_cond(t, rnp->boost_kthread_status);
+		rcu_wake_cond(rnp->boost_kthread_task,
+			      rnp->boost_kthread_status);
 	} else {
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	}
@@ -1649,98 +1531,6 @@ static void rcu_cleanup_after_idle(void)
 
 #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
 
-#ifdef CONFIG_RCU_FAST_NO_HZ
-
-static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
-{
-	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
-
-	sprintf(cp, "last_accelerate: %04lx/%04lx, Nonlazy posted: %c%c%c",
-		rdp->last_accelerate & 0xffff, jiffies & 0xffff,
-		".l"[rdp->all_lazy],
-		".L"[!rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)],
-		".D"[!rdp->tick_nohz_enabled_snap]);
-}
-
-#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
-
-static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
-{
-	*cp = '\0';
-}
-
-#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */
-
-/* Initiate the stall-info list. */
-static void print_cpu_stall_info_begin(void)
-{
-	pr_cont("\n");
-}
-
-/*
- * Print out diagnostic information for the specified stalled CPU.
- *
- * If the specified CPU is aware of the current RCU grace period, then
- * print the number of scheduling clock interrupts the CPU has taken
- * during the time that it has been aware.  Otherwise, print the number
- * of RCU grace periods that this CPU is ignorant of, for example, "1"
- * if the CPU was aware of the previous grace period.
- *
- * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info.
- */
-static void print_cpu_stall_info(int cpu)
-{
-	unsigned long delta;
-	char fast_no_hz[72];
-	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
-	char *ticks_title;
-	unsigned long ticks_value;
-
-	/*
-	 * We could be printing a lot while holding a spinlock.  Avoid
-	 * triggering hard lockup.
-	 */
-	touch_nmi_watchdog();
-
-	ticks_value = rcu_seq_ctr(rcu_state.gp_seq - rdp->gp_seq);
-	if (ticks_value) {
-		ticks_title = "GPs behind";
-	} else {
-		ticks_title = "ticks this GP";
-		ticks_value = rdp->ticks_this_gp;
-	}
-	print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
-	delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq);
-	pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%#lx softirq=%u/%u fqs=%ld %s\n",
-	       cpu,
-	       "O."[!!cpu_online(cpu)],
-	       "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],
-	       "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)],
-	       !IS_ENABLED(CONFIG_IRQ_WORK) ? '?' :
-			rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :
-				"!."[!delta],
-	       ticks_value, ticks_title,
-	       rcu_dynticks_snap(rdp) & 0xfff,
-	       rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
-	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
-	       READ_ONCE(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
-	       fast_no_hz);
-}
-
-/* Terminate the stall-info list. */
-static void print_cpu_stall_info_end(void)
-{
-	pr_err("\t");
-}
-
-/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */
-static void zero_cpu_stall_ticks(struct rcu_data *rdp)
-{
-	rdp->ticks_this_gp = 0;
-	rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id());
-	WRITE_ONCE(rdp->last_fqs_resched, jiffies);
-}
-
 #ifdef CONFIG_RCU_NOCB_CPU
 
 /*
@@ -1766,11 +1556,22 @@ static void zero_cpu_stall_ticks(struct rcu_data *rdp)
  */
 
 
-/* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */
+/*
+ * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
+ * The string after the "rcu_nocbs=" is either "all" for all CPUs, or a
+ * comma-separated list of CPUs and/or CPU ranges.  If an invalid list is
+ * given, a warning is emitted and all CPUs are offloaded.
+ */
 static int __init rcu_nocb_setup(char *str)
 {
 	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
-	cpulist_parse(str, rcu_nocb_mask);
+	if (!strcasecmp(str, "all"))
+		cpumask_setall(rcu_nocb_mask);
+	else
+		if (cpulist_parse(str, rcu_nocb_mask)) {
+			pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
+			cpumask_setall(rcu_nocb_mask);
+		}
 	return 1;
 }
 __setup("rcu_nocbs=", rcu_nocb_setup);

kernel/rcu/update.c

@@ -424,68 +424,11 @@ EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
 #endif
 
 #ifdef CONFIG_RCU_STALL_COMMON
-
-#ifdef CONFIG_PROVE_RCU
-#define RCU_STALL_DELAY_DELTA	       (5 * HZ)
-#else
-#define RCU_STALL_DELAY_DELTA	       0
-#endif
-
 int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
-static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
-
 module_param(rcu_cpu_stall_suppress, int, 0644);
+int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
 module_param(rcu_cpu_stall_timeout, int, 0644);
-
-int rcu_jiffies_till_stall_check(void)
-{
-	int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);
-
-	/*
-	 * Limit check must be consistent with the Kconfig limits
-	 * for CONFIG_RCU_CPU_STALL_TIMEOUT.
-	 */
-	if (till_stall_check < 3) {
-		WRITE_ONCE(rcu_cpu_stall_timeout, 3);
-		till_stall_check = 3;
-	} else if (till_stall_check > 300) {
-		WRITE_ONCE(rcu_cpu_stall_timeout, 300);
-		till_stall_check = 300;
-	}
-	return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
-}
-EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
-
-void rcu_sysrq_start(void)
-{
-	if (!rcu_cpu_stall_suppress)
-		rcu_cpu_stall_suppress = 2;
-}
-
-void rcu_sysrq_end(void)
-{
-	if (rcu_cpu_stall_suppress == 2)
-		rcu_cpu_stall_suppress = 0;
-}
-
-static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
-{
-	rcu_cpu_stall_suppress = 1;
-	return NOTIFY_DONE;
-}
-
-static struct notifier_block rcu_panic_block = {
-	.notifier_call = rcu_panic,
-};
-
-static int __init check_cpu_stall_init(void)
-{
-	atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
-	return 0;
-}
-early_initcall(check_cpu_stall_init);
-
 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 
 #ifdef CONFIG_TASKS_RCU

kernel/torture.c

@@ -88,6 +88,8 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
 
 	if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
 		return false;
+	if (num_online_cpus() <= 1)
+		return false;  /* Can't offline the last CPU. */
 
 	if (verbose > 1)
 		pr_alert("%s" TORTURE_FLAG

net/ipv4/netfilter/ipt_CLUSTERIP.c

@@ -56,7 +56,7 @@ struct clusterip_config {
 #endif
 	enum clusterip_hashmode hash_mode;	/* which hashing mode */
 	u_int32_t hash_initval;			/* hash initialization */
-	struct rcu_head rcu;			/* for call_rcu_bh */
+	struct rcu_head rcu;			/* for call_rcu */
 	struct net *net;			/* netns for pernet list */
 	char ifname[IFNAMSIZ];			/* device ifname */
 };

tools/memory-model/README

@@ -20,13 +20,17 @@ that litmus test to be exercised within the Linux kernel.
 REQUIREMENTS
 ============
 
-Version 7.49 of the "herd7" and "klitmus7" tools must be downloaded
-separately:
+Version 7.52 or higher of the "herd7" and "klitmus7" tools must be
+downloaded separately:
 
   https://github.com/herd/herdtools7
 
 See "herdtools7/INSTALL.md" for installation instructions.
 
+Note that although these tools usually provide backwards compatibility,
+this is not absolutely guaranteed.  Therefore, if a later version does
+not work, please try using the exact version called out above.
+
 
 ==================
 BASIC USAGE: HERD7
@@ -221,8 +225,29 @@ The Linux-kernel memory model has the following limitations:
 		additional call_rcu() process to the site of the
 		emulated rcu-barrier().
 
-	e.	Sleepable RCU (SRCU) is not modeled.  It can be
-		emulated, but perhaps not simply.
+	e.	Although sleepable RCU (SRCU) is now modeled, there
+		are some subtle differences between its semantics and
+		those in the Linux kernel.  For example, the kernel
+		might interpret the following sequence as two partially
+		overlapping SRCU read-side critical sections:
+
+			 1  r1 = srcu_read_lock(&my_srcu);
+			 2  do_something_1();
+			 3  r2 = srcu_read_lock(&my_srcu);
+			 4  do_something_2();
+			 5  srcu_read_unlock(&my_srcu, r1);
+			 6  do_something_3();
+			 7  srcu_read_unlock(&my_srcu, r2);
+
+		In contrast, LKMM will interpret this as a nested pair of
+		SRCU read-side critical sections, with the outer critical
+		section spanning lines 1-7 and the inner critical section
+		spanning lines 3-5.
+
+		This difference would be more of a concern had anyone
+		identified a reasonable use case for partially overlapping
+		SRCU read-side critical sections.  For more information,
+		please see: https://paulmck.livejournal.com/40593.html
 
 	f.	Reader-writer locking is not modeled.  It can be
 		emulated in litmus tests using atomic read-modify-write

tools/memory-model/linux-kernel.bell

@@ -33,8 +33,14 @@ enum Barriers = 'wmb (*smp_wmb*) ||
 		'after-unlock-lock (*smp_mb__after_unlock_lock*)
 instructions F[Barriers]
 
+(* SRCU *)
+enum SRCU = 'srcu-lock || 'srcu-unlock || 'sync-srcu
+instructions SRCU[SRCU]
+(* All srcu events *)
+let Srcu = Srcu-lock | Srcu-unlock | Sync-srcu
+
 (* Compute matching pairs of nested Rcu-lock and Rcu-unlock *)
-let matched = let rec
+let rcu-rscs = let rec
 	    unmatched-locks = Rcu-lock \ domain(matched)
 	and unmatched-unlocks = Rcu-unlock \ range(matched)
 	and unmatched = unmatched-locks | unmatched-unlocks
@@ -46,8 +52,27 @@ let matched = let rec
 	in matched
 
 (* Validate nesting *)
-flag ~empty Rcu-lock \ domain(matched) as unbalanced-rcu-locking
-flag ~empty Rcu-unlock \ range(matched) as unbalanced-rcu-locking
+flag ~empty Rcu-lock \ domain(rcu-rscs) as unbalanced-rcu-locking
+flag ~empty Rcu-unlock \ range(rcu-rscs) as unbalanced-rcu-locking
+
+(* Compute matching pairs of nested Srcu-lock and Srcu-unlock *)
+let srcu-rscs = let rec
+	    unmatched-locks = Srcu-lock \ domain(matched)
+	and unmatched-unlocks = Srcu-unlock \ range(matched)
+	and unmatched = unmatched-locks | unmatched-unlocks
+	and unmatched-po = ([unmatched] ; po ; [unmatched]) & loc
+	and unmatched-locks-to-unlocks =
+		([unmatched-locks] ; po ; [unmatched-unlocks]) & loc
+	and matched = matched | (unmatched-locks-to-unlocks \
+		(unmatched-po ; unmatched-po))
+	in matched
+
+(* Validate nesting *)
+flag ~empty Srcu-lock \ domain(srcu-rscs) as unbalanced-srcu-locking
+flag ~empty Srcu-unlock \ range(srcu-rscs) as unbalanced-srcu-locking
+
+(* Check for use of synchronize_srcu() inside an RCU critical section *)
+flag ~empty rcu-rscs & (po ; [Sync-srcu] ; po) as invalid-sleep
 
-(* Outermost level of nesting only *)
-let crit = matched \ (po^-1 ; matched ; po^-1)
+(* Validate SRCU dynamic match *)
+flag ~empty different-values(srcu-rscs) as srcu-bad-nesting

tools/memory-model/linux-kernel.cat

@@ -33,7 +33,7 @@ let mb = ([M] ; fencerel(Mb) ; [M]) |
 	([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) |
 	([M] ; po ; [UL] ; (co | po) ; [LKW] ;
 		fencerel(After-unlock-lock) ; [M])
-let gp = po ; [Sync-rcu] ; po?
+let gp = po ; [Sync-rcu | Sync-srcu] ; po?
 
 let strong-fence = mb | gp
 
@@ -91,32 +91,47 @@ acyclic pb as propagation
 (*******)
 
 (*
- * Effect of read-side critical section proceeds from the rcu_read_lock()
- * onward on the one hand and from the rcu_read_unlock() backwards on the
- * other hand.
+ * Effects of read-side critical sections proceed from the rcu_read_unlock()
+ * or srcu_read_unlock() backwards on the one hand, and from the
+ * rcu_read_lock() or srcu_read_lock() forwards on the other hand.
+ *
+ * In the definition of rcu-fence below, the po term at the left-hand side
+ * of each disjunct and the po? term at the right-hand end have been factored
+ * out.  They have been moved into the definitions of rcu-link and rb.
+ * This was necessary in order to apply the "& loc" tests correctly.
  *)
-let rscs = po ; crit^-1 ; po?
+let rcu-gp = [Sync-rcu]		(* Compare with gp *)
+let srcu-gp = [Sync-srcu]
+let rcu-rscsi = rcu-rscs^-1
+let srcu-rscsi = srcu-rscs^-1
 
 (*
  * The synchronize_rcu() strong fence is special in that it can order not
  * one but two non-rf relations, but only in conjunction with an RCU
  * read-side critical section.
  *)
-let rcu-link = hb* ; pb* ; prop
+let rcu-link = po? ; hb* ; pb* ; prop ; po
 
 (*
  * Any sequence containing at least as many grace periods as RCU read-side
  * critical sections (joined by rcu-link) acts as a generalized strong fence.
+ * Likewise for SRCU grace periods and read-side critical sections, provided
+ * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same
+ * struct srcu_struct location.
  *)
-let rec rcu-fence = gp |
-	(gp ; rcu-link ; rscs) |
-	(rscs ; rcu-link ; gp) |
-	(gp ; rcu-link ; rcu-fence ; rcu-link ; rscs) |
-	(rscs ; rcu-link ; rcu-fence ; rcu-link ; gp) |
+let rec rcu-fence = rcu-gp | srcu-gp |
+	(rcu-gp ; rcu-link ; rcu-rscsi) |
+	((srcu-gp ; rcu-link ; srcu-rscsi) & loc) |
+	(rcu-rscsi ; rcu-link ; rcu-gp) |
+	((srcu-rscsi ; rcu-link ; srcu-gp) & loc) |
+	(rcu-gp ; rcu-link ; rcu-fence ; rcu-link ; rcu-rscsi) |
+	((srcu-gp ; rcu-link ; rcu-fence ; rcu-link ; srcu-rscsi) & loc) |
+	(rcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; rcu-gp) |
+	((srcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; srcu-gp) & loc) |
 	(rcu-fence ; rcu-link ; rcu-fence)
 
 (* rb orders instructions just as pb does *)
-let rb = prop ; rcu-fence ; hb* ; pb*
+let rb = prop ; po ; rcu-fence ; po? ; hb* ; pb*
 
 irreflexive rb as rcu
 

tools/memory-model/linux-kernel.def

@@ -47,6 +47,12 @@ rcu_read_unlock() { __fence{rcu-unlock}; }
 synchronize_rcu() { __fence{sync-rcu}; }
 synchronize_rcu_expedited() { __fence{sync-rcu}; }
 
+// SRCU
+srcu_read_lock(X)  __srcu{srcu-lock}(X)
+srcu_read_unlock(X,Y) { __srcu{srcu-unlock}(X,Y); }
+synchronize_srcu(X)  { __srcu{sync-srcu}(X); }
+synchronize_srcu_expedited(X)  { __srcu{sync-srcu}(X); }
+
 // Atomic
 atomic_read(X) READ_ONCE(*X)
 atomic_set(X,V) { WRITE_ONCE(*X,V); }

tools/memory-model/lock.cat

@@ -6,9 +6,6 @@
 
 (*
  * Generate coherence orders and handle lock operations
- *
- * Warning: spin_is_locked() crashes herd7 versions strictly before 7.48.
- * spin_is_locked() is functional from herd7 version 7.49.
  *)
 
 include "cross.cat"

tools/testing/selftests/rcutorture/bin/configNR_CPUS.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Extract the number of CPUs expected from the specified Kconfig-file
 # fragment by checking CONFIG_SMP and CONFIG_NR_CPUS.  If the specified
@@ -7,23 +8,9 @@
 #
 # Usage: configNR_CPUS.sh config-frag
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2013
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 cf=$1
 if test ! -r $cf

tools/testing/selftests/rcutorture/bin/config_override.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # config_override.sh base override
 #
@@ -6,23 +7,9 @@
 # that conflict with any in override, concatenating what remains and
 # sending the result to standard output.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2017
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 base=$1
 if test -r $base

tools/testing/selftests/rcutorture/bin/configcheck.sh

 #!/bin/bash
-# Usage: configcheck.sh .config .config-template
-#
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
+# SPDX-License-Identifier: GPL-2.0+
 #
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
+# Usage: configcheck.sh .config .config-template
 #
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 T=${TMPDIR-/tmp}/abat-chk-config.sh.$$
 trap 'rm -rf $T' 0
@@ -26,6 +14,7 @@ mkdir $T
 cat $1 > $T/.config
 
 cat $2 | sed -e 's/\(.*\)=n/# \1 is not set/' -e 's/^#CHECK#//' |
+grep -v '^CONFIG_INITRAMFS_SOURCE' |
 awk	'
 {
 		print "if grep -q \"" $0 "\" < '"$T/.config"'";

tools/testing/selftests/rcutorture/bin/configinit.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Usage: configinit.sh config-spec-file build-output-dir results-dir
 #
@@ -14,23 +15,9 @@
 # for example, "O=/tmp/foo".  If this argument is omitted, the .config
 # file will be generated directly in the current directory.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2013
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 T=${TMPDIR-/tmp}/configinit.sh.$$
 trap 'rm -rf $T' 0

tools/testing/selftests/rcutorture/bin/cpus2use.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Get an estimate of how CPU-hoggy to be.
 #
 # Usage: cpus2use.sh
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2013
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 ncpus=`grep '^processor' /proc/cpuinfo | wc -l`
 idlecpus=`mpstat | tail -1 | \

tools/testing/selftests/rcutorture/bin/functions.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Shell functions for the rest of the scripts.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2013
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 # bootparam_hotplug_cpu bootparam-string
 #

tools/testing/selftests/rcutorture/bin/jitter.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Alternate sleeping and spinning on randomly selected CPUs.  The purpose
 # of this script is to inflict random OS jitter on a concurrently running
@@ -11,23 +12,9 @@
 # sleepmax: Maximum microseconds to sleep, defaults to one second.
 # spinmax: Maximum microseconds to spin, defaults to one millisecond.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2016
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 me=$(($1 * 1000))
 duration=$2

tools/testing/selftests/rcutorture/bin/kvm-build.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Build a kvm-ready Linux kernel from the tree in the current directory.
 #
 # Usage: kvm-build.sh config-template build-dir resdir
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 config_template=${1}
 if test -z "$config_template" -o ! -f "$config_template" -o ! -r "$config_template"

tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh

 #!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Invoke a text editor on all console.log files for all runs with diagnostics,
 # that is, on all such files having a console.log.diags counterpart.
@@ -10,6 +11,10 @@
 #
 # The "directory" above should end with the date/time directory, for example,
 # "tools/testing/selftests/rcutorture/res/2018.02.25-14:27:27".
+#
+# Copyright (C) IBM Corporation, 2018
+#
+# Author: Paul E. McKenney <paulmck@linux.ibm.com>
 
 rundir="${1}"
 if test -z "$rundir" -o ! -d "$rundir"

tools/testing/selftests/rcutorture/bin/kvm-recheck-lock.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Analyze a given results directory for locktorture progress.
 #
 # Usage: kvm-recheck-lock.sh resdir
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2014
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 i="$1"
 if test -d "$i" -a -r "$i"

tools/testing/selftests/rcutorture/bin/kvm-recheck-rcu.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Analyze a given results directory for rcutorture progress.
 #
 # Usage: kvm-recheck-rcu.sh resdir
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2014
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 i="$1"
 if test -d "$i" -a -r "$i"

tools/testing/selftests/rcutorture/bin/kvm-recheck-rcuperf-ftrace.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Analyze a given results directory for rcuperf performance measurements,
 # looking for ftrace data.  Exits with 0 if data was found, analyzed, and
@@ -7,23 +8,9 @@
 #
 # Usage: kvm-recheck-rcuperf-ftrace.sh resdir
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2016
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 i="$1"
 . functions.sh

tools/testing/selftests/rcutorture/bin/kvm-recheck-rcuperf.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Analyze a given results directory for rcuperf performance measurements.
 #
 # Usage: kvm-recheck-rcuperf.sh resdir
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2016
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 i="$1"
 if test -d "$i" -a -r "$i"

tools/testing/selftests/rcutorture/bin/kvm-recheck.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Given the results directories for previous KVM-based torture runs,
 # check the build and console output for errors.  Given a directory
@@ -6,23 +7,9 @@
 #
 # Usage: kvm-recheck.sh resdir ...
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 PATH=`pwd`/tools/testing/selftests/rcutorture/bin:$PATH; export PATH
 . functions.sh

tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Run a kvm-based test of the specified tree on the specified configs.
 # Fully automated run and error checking, no graphics console.
@@ -20,23 +21,9 @@
 #
 # More sophisticated argument parsing is clearly needed.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 T=${TMPDIR-/tmp}/kvm-test-1-run.sh.$$
 trap 'rm -rf $T' 0

tools/testing/selftests/rcutorture/bin/kvm.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Run a series of tests under KVM.  By default, this series is specified
 # by the relevant CFLIST file, but can be overridden by the --configs
@@ -6,23 +7,9 @@
 #
 # Usage: kvm.sh [ options ]
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 scriptname=$0
 args="$*"

tools/testing/selftests/rcutorture/bin/mkinitrd.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Create an initrd directory if one does not already exist.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2013
 #
 # Author: Connor Shu <Connor.Shu@ibm.com>

tools/testing/selftests/rcutorture/bin/parse-build.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Check the build output from an rcutorture run for goodness.
 # The "file" is a pathname on the local system, and "title" is
@@ -8,23 +9,9 @@
 #
 # Usage: parse-build.sh file title
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 F=$1
 title=$2

tools/testing/selftests/rcutorture/bin/parse-console.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Check the console output from an rcutorture run for oopses.
 # The "file" is a pathname on the local system, and "title" is
@@ -6,23 +7,9 @@
 #
 # Usage: parse-console.sh file title
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2011
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 T=${TMPDIR-/tmp}/parse-console.sh.$$
 file="$1"

tools/testing/selftests/rcutorture/configs/lock/ver_functions.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Kernel-version-dependent shell functions for the rest of the scripts.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2014
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 # locktorture_param_onoff bootparam-string config-file
 #

tools/testing/selftests/rcutorture/configs/rcu/ver_functions.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Kernel-version-dependent shell functions for the rest of the scripts.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2013
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 # rcutorture_param_n_barrier_cbs bootparam-string
 #

tools/testing/selftests/rcutorture/configs/rcuperf/ver_functions.sh

 #!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Torture-suite-dependent shell functions for the rest of the scripts.
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
 # Copyright (C) IBM Corporation, 2015
 #
-# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
 # per_version_boot_params bootparam-string config-file seconds
 #