Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD

cpu.2014.11.03a: Changes for per-CPU variables.
doc.2014.11.13a: Documentation updates.
fixes.2014.11.13a: Miscellaneous fixes.
signal.2014.10.29a: Signal changes.
rt.2014.10.29a: Real-time changes.
torture.2014.11.03a: torture-test changes.

This commit affines rcu_tasks_kthread() to the housekeeping CPUs
in CONFIG_NO_HZ_FULL builds.  This is just a default, so systems
administrators are free to put this kthread somewhere else if they wish.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The comment above rcu_read_unlock() explains the potential deadlock
if the caller holds one of the locks taken by rt_mutex_unlock() paths,
but it is not clear from this documentation that any lock which can
be taken from interrupt can lead to deadlock as well and we need to
take rt_mutex_lock() into account too.

The problem is that rt_mutex_lock() takes wait_lock without disabling
irqs, and thus an interrupt taking some LOCK can obviously race with
rcu_read_unlock_special() called with the same LOCK held.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The current implementation of cond_resched_rcu_qs() can invoke
rcu_note_voluntary_context_switch() twice in the should_resched()
case, once via the call to __schedule() and once directly.  However, as
noted by Joe Lawrence in a patch to the team subsystem, cond_resched()
returns an indication as to whether or not the call to __schedule()
actually happened.  This commit therefore changes cond_resched_rcu_qs()
so as to invoke rcu_note_voluntary_context_switch() only when __schedule()
was not called.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Add a sparse check when RCU_INIT_POINTER() is used to assign a non __rcu
annotated pointer.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Correct the example of memory orderings in memory-barriers.txt

Commit 615cc2c9 "Documentation/memory-barriers.txt: fix important typo re
memory barriers" changed the assignment to x and y. Change the rest of the
example to match this change.
Reported-by: Ganesh Rapolu <ganesh.rapolu@hotmail.com>
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Short-circuit booleans are not defences against compilers breaking
your intended control dependencies.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Document the RCU self test boot parameters in kernel-parameters.txt.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Commit 38706bc5 (rcutorture: Add callback-flood test) vmalloc()ed
a bunch of RCU callbacks, but failed to free them.  This commit fixes
that oversight.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Now that we have removed configs based on kernel version, we can also remove the
kversion parameter in kvm.sh.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Remove rcutorture configuration files which are no longer necessary.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Add config and boot parameters to enable the self tests in rcutorture testing.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Add early boot self tests for RCU under CONFIG_PROVE_RCU.

Currently the only test is adding a dummy callback which increments a counter
which we then later verify after calling rcu_barrier*().
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The rcutorture scripts create a qemu-cmd script containing the actual
qemu command.  However, this command references the build directory,
which will be overwritten by later builds.  This commit therefore runs
the kernel out of the results directory so that less hand-editing is
required to re-run a previous test.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

A long string of get_online_cpus() with each followed by a
put_online_cpu() that fails to acquire cpu_hotplug.lock can result in
overflow of the cpu_hotplug.puts_pending counter.  Although this is
perhaps improbably, a system with absolutely no CPU-hotplug operations
will have an arbitrarily long time in which this overflow could occur.
This commit therefore adds overflow checks to get_online_cpus() and
try_get_online_cpus().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The "cpu" argument to rcu_cleanup_after_idle() is always the current
CPU, so drop it.  This moves the smp_processor_id() from the caller to
rcu_cleanup_after_idle(), saving argument-passing overhead.  Again,
the anticipated cross-CPU uses of these functions has been replaced
by NO_HZ_FULL.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The "cpu" argument to rcu_prepare_for_idle() is always the current
CPU, so drop it.  This in turn allows two of the uses of "cpu" in
this function to be replaced with a this_cpu_ptr() and the third by
smp_processor_id(), replacing that of the call to rcu_prepare_for_idle().
Again, the anticipated cross-CPU uses of these functions has been replaced
by NO_HZ_FULL.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The "cpu" argument to rcu_needs_cpu() is always the current CPU, so drop
it.  This in turn allows the "cpu" argument to rcu_cpu_has_callbacks()
to be removed, which allows the uses of "cpu" in both functions to be
replaced with a this_cpu_ptr().  Again, the anticipated cross-CPU uses
of these functions has been replaced by NO_HZ_FULL.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The "cpu" argument to rcu_note_context_switch() is always the current
CPU, so drop it.  This in turn allows the "cpu" argument to
rcu_preempt_note_context_switch() to be removed, which allows the sole
use of "cpu" in both functions to be replaced with a this_cpu_ptr().
Again, the anticipated cross-CPU uses of these functions has been
replaced by NO_HZ_FULL.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Because rcu_preempt_check_callbacks()'s argument is guaranteed to
always be the current CPU, drop the argument and replace per_cpu()
with __this_cpu_read().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Because rcu_pending()'s argument is guaranteed to always be the current
CPU, drop the argument and replace per_cpu_ptr() with this_cpu_ptr().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The "cpu" argument was kept around on the off-chance that RCU might
offload scheduler-clock interrupts.  However, this offload approach
has been replaced by NO_HZ_FULL, which offloads -all- RCU processing
from qualifying CPUs.  It is therefore time to remove the "cpu" argument
to rcu_check_callbacks(), which this commit does.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The rcu_data per-CPU variable has a number of fields that are atomically
manipulated, potentially by any CPU.  This situation can result in false
sharing with per-CPU variables that have the misfortune of being allocated
adjacent to rcu_data in memory.  This commit therefore changes the
DEFINE_PER_CPU() to DEFINE_PER_CPU_SHARED_ALIGNED() in order to avoid
this false sharing.
Reported-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

For some functions in kernel/rcu/tree* the rdtp parameter is always
this_cpu_ptr(rdtp).  Remove the parameter if constant and calculate the
pointer in function.

This will have the advantage that it is obvious that the address are
all per cpu offsets and thus it will enable the use of this_cpu_ops in
the future.
Signed-off-by: Christoph Lameter <cl@linux.com>
[ paulmck: Forward-ported to rcu/dev, whitespace adjustment. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Commit 35ce7f29 (rcu: Create rcuo kthreads only for onlined CPUs)
contains checks for the case where CPUs are brought online out of
order, re-wiring the rcuo leader-follower relationships as needed.
Unfortunately, this rewiring was broken.  This apparently went undetected
due to the tendency of systems to bring CPUs online in order.  This commit
nevertheless fixes the rewiring.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

If a no-CBs CPU were to post an RCU callback with interrupts disabled
after it entered the idle loop for the last time, there might be no
deferred wakeup for the corresponding rcuo kthreads.  This commit
therefore adds a set of calls to do_nocb_deferred_wakeup() after the
CPU has gone completely offline.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after
TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU
and uses PREEMPT_RCU config option in its place.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this
value for both the per-CPU kthreads (rcuc/N) and the rcu boosting
threads (rcub/n).

Also, create the module_parameter rcutree.kthread_prio to be used on
the kernel command line at boot to set a new value (rcutree.kthread_prio=N).
Signed-off-by: Clark Williams <clark.williams@gmail.com>
[ paulmck: Ported to rcu/dev, applied Paul Bolle and Peter Zijlstra feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

__cleanup_sighand() frees sighand without RCU grace period. This is
correct but this looks "obviously buggy" and constantly confuses the
readers, add the comments to explain how this works.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The kill_pid_info() can potentially loop indefinitely if tasks are created
and deleted sufficiently quickly, and if this happens, this function
will remain in a single RCU read-side critical section indefinitely.
This commit therefore exits the RCU read-side critical section on each
pass through the loop.  Because a race must happen to retry the loop,
this should have no performance impact in the common case.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Currently, synchronize_sched_expedited() sends IPIs to all online CPUs,
even those that are idle or executing in nohz_full= userspace.  Because
idle CPUs and nohz_full= userspace CPUs are in extended quiescent states,
there is no need to IPI them in the first place.  This commit therefore
avoids IPIing CPUs that are already in extended quiescent states.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

There are some RCU_BOOST-specific per-CPU variable declarations that
are needlessly defined under #ifdef in kernel/rcu/tree.c.  This commit
therefore moves these declarations into a pre-existing #ifdef in
kernel/rcu/tree_plugin.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Every choice item of the "Build-forced no-CBs CPUs" choice had a
dependency to RCU_NOCB_CPU.  It's more comprehensible if the choice
itself has the dependency instead of every choice item.  The choice
itself doesn't need to be visible if there are no items selectable
(i.e.  on arch/frv) or RCU_NOCB_CPU is not defined.
Signed-off-by: Stefan Hengelein <stefan.hengelein@fau.de>
Signed-off-by: Andreas Ruprecht <rupran@einserver.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The CONFIG_RCU_CPU_STALL_VERBOSE Kconfig parameter causes preemptible
RCU's CPU stall warnings to dump out any preempted tasks that are blocking
the current RCU grace period.  This information is useful, and the default
has been CONFIG_RCU_CPU_STALL_VERBOSE=y for some years.  It is therefore
time for this commit to remove this Kconfig parameter, so that future
kernel builds will always act as if CONFIG_RCU_CPU_STALL_VERBOSE=y.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Commit 35ce7f29 (rcu: Create rcuo kthreads only for onlined CPUs)
avoids creating rcuo kthreads for CPUs that never come online.  This
fixes a bug in many instances of firmware: Instead of lying about their
age, these systems instead lie about the number of CPUs that they have.
Before commit 35ce7f29, this could result in huge numbers of useless
rcuo kthreads being created.

It appears that experience indicates that I should have told the
people suffering from this problem to fix their broken firmware, but
I instead produced what turned out to be a partial fix.   The missing
piece supplied by this commit makes sure that rcu_barrier() knows not to
post callbacks for no-CBs CPUs that have not yet come online, because
otherwise rcu_barrier() will hang on systems having firmware that lies
about the number of CPUs.

It is tempting to simply have rcu_barrier() refuse to post a callback on
any no-CBs CPU that does not have an rcuo kthread.  This unfortunately
does not work because rcu_barrier() is required to wait for all pending
callbacks.  It is therefore required to wait even for those callbacks
that cannot possibly be invoked.  Even if doing so hangs the system.

Given that posting a callback to a no-CBs CPU that does not yet have an
rcuo kthread can hang rcu_barrier(), It is tempting to report an error
in this case.  Unfortunately, this will result in false positives at
boot time, when it is perfectly legal to post callbacks to the boot CPU
before the scheduler has started, in other words, before it is legal
to invoke rcu_barrier().

So this commit instead has rcu_barrier() avoid posting callbacks to
CPUs having neither rcuo kthread nor pending callbacks, and has it
complain bitterly if it finds CPUs having no rcuo kthread but some
pending callbacks.  And when rcu_barrier() does find CPUs having no rcuo
kthread but pending callbacks, as noted earlier, it has no choice but
to hang indefinitely.
Reported-by: Yanko Kaneti <yaneti@declera.com>
Reported-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Reported-by: Meelis Roos <mroos@linux.ee>
Reported-by: Eric B Munson <emunson@akamai.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Eric B Munson <emunson@akamai.com>
Tested-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Tested-by: Yanko Kaneti <yaneti@declera.com>
Tested-by: Kevin Fenzi <kevin@scrye.com>
Tested-by: Meelis Roos <mroos@linux.ee>

Commit dd56af42 (rcu: Eliminate deadlock between CPU hotplug and
expedited grace periods) was incomplete.  Although it did eliminate
deadlocks involving synchronize_sched_expedited()'s acquisition of
cpu_hotplug.lock via get_online_cpus(), it did nothing about the similar
deadlock involving acquisition of this same lock via put_online_cpus().
This deadlock became apparent with testing involving hibernation.

This commit therefore changes put_online_cpus() acquisition of this lock
to be conditional, and increments a new cpu_hotplug.puts_pending field
in case of acquisition failure.  Then cpu_hotplug_begin() checks for this
new field being non-zero, and applies any changes to cpu_hotplug.refcount.
Reported-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Tested-by: Borislav Petkov <bp@suse.de>

Pull ARM SoC fixes from Olof Johansson:
 "A batch of fixes that have come in during the merge window.

  Some of them are defconfig updates for things that have now landed,
  some errata additions and a few general scattered fixes.

  There's also a qcom DT update that adds support for SATA on AP148, and
  basic support for Sony Xperia Z1 and CM-QS600 platforms that seemed
  isolated enough that we could merge it even if it's late"

* tag 'arm-soc-fixes-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  MAINTAINERS: corrected bcm2835 search
  ARM: dts: Explicitly set dr_mode on exynos5420-arndale-octa
  ARM: dts: Explicitly set dr_mode on exynos Peach boards
  ARM: dts: qcom: add CM-QS600 board
  ARM: dts: qcom: Add initial DTS file for Sony Xperia Z1 phone
  ARM: dts: qcom: Add SATA support on IPQ8064/AP148
  MAINTAINERS: Update Santosh Shilimkar's email id
  ARM: sunxi_defconfig: enable CONFIG_REGULATOR
  ARM: dts: Disable smc91x on n900 until bootloader dependency is removed
  ARM: omap2plus_defconfig: Enable ARM erratum 430973 for omap3
  ARM: exynos_defconfig: enable USB gadget support
  ARM: exynos_defconfig: Enable Maxim 77693 and I2C GPIO drivers
  ARM: mm: Fix ifdef around cpu_*_do_[suspend, resume] ops
  ARM: EXYNOS: Fix build with PM_SLEEP=n and ARM_EXYNOS_CPUIDLE=n
  ARM: SAMSUNG: Restore Samsung PM Debug functionality
  ARM: dts: Fix pull setting in sd4_width8 pin group for exynos4x12
  ARM: exynos_defconfig: Enable SBS battery support
  ARM: exynos_defconfig: Enable Control Groups support
  ARM: exynos_defconfig: Enable Atmel maXTouch support
  ARM: exynos_defconfig: Enable MAX77802

Pull audit updates from Eric Paris:
 "So this change across a whole bunch of arches really solves one basic
  problem.  We want to audit when seccomp is killing a process.  seccomp
  hooks in before the audit syscall entry code.  audit_syscall_entry
  took as an argument the arch of the given syscall.  Since the arch is
  part of what makes a syscall number meaningful it's an important part
  of the record, but it isn't available when seccomp shoots the
  syscall...

  For most arch's we have a better way to get the arch (syscall_get_arch)
  So the solution was two fold: Implement syscall_get_arch() everywhere
  there is audit which didn't have it.  Use syscall_get_arch() in the
  seccomp audit code.  Having syscall_get_arch() everywhere meant it was
  a useless flag on the stack and we could get rid of it for the typical
  syscall entry.

  The other changes inside the audit system aren't grand, fixed some
  records that had invalid spaces.  Better locking around the task comm
  field.  Removing some dead functions and structs.  Make some things
  static.  Really minor stuff"

* git://git.infradead.org/users/eparis/audit: (31 commits)
  audit: rename audit_log_remove_rule to disambiguate for trees
  audit: cull redundancy in audit_rule_change
  audit: WARN if audit_rule_change called illegally
  audit: put rule existence check in canonical order
  next: openrisc: Fix build
  audit: get comm using lock to avoid race in string printing
  audit: remove open_arg() function that is never used
  audit: correct AUDIT_GET_FEATURE return message type
  audit: set nlmsg_len for multicast messages.
  audit: use union for audit_field values since they are mutually exclusive
  audit: invalid op= values for rules
  audit: use atomic_t to simplify audit_serial()
  kernel/audit.c: use ARRAY_SIZE instead of sizeof/sizeof[0]
  audit: reduce scope of audit_log_fcaps
  audit: reduce scope of audit_net_id
  audit: arm64: Remove the audit arch argument to audit_syscall_entry
  arm64: audit: Add audit hook in syscall_trace_enter/exit()
  audit: x86: drop arch from __audit_syscall_entry() interface
  sparc: implement is_32bit_task
  sparc: properly conditionalize use of TIF_32BIT
  ...