Those two APIs were provided to optimize the calls of
tick_nohz_idle_enter() and rcu_idle_enter() into a single
irq disabled section. This way no interrupt happening in-between would
needlessly process any RCU job.

Now we are talking about an optimization for which benefits
have yet to be measured. Let's start simple and completely decouple
idle rcu and dyntick idle logics to simplify.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

It is assumed that rcu won't be used once we switch to tickless
mode and until we restart the tick. However this is not always
true, as in x86-64 where we dereference the idle notifiers after
the tick is stopped.

To prepare for fixing this, add two new APIs:
tick_nohz_idle_enter_norcu() and tick_nohz_idle_exit_norcu().

If no use of RCU is made in the idle loop between
tick_nohz_enter_idle() and tick_nohz_exit_idle() calls, the arch
must instead call the new *_norcu() version such that the arch doesn't
need to call rcu_idle_enter() and rcu_idle_exit().

Otherwise the arch must call tick_nohz_enter_idle() and
tick_nohz_exit_idle() and also call explicitly:

- rcu_idle_enter() after its last use of RCU before the CPU is put
to sleep.
- rcu_idle_exit() before the first use of RCU after the CPU is woken
up.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The tick_nohz_stop_sched_tick() function, which tries to delay
the next timer tick as long as possible, can be called from two
places:

- From the idle loop to start the dytick idle mode
- From interrupt exit if we have interrupted the dyntick
idle mode, so that we reprogram the next tick event in
case the irq changed some internal state that requires this
action.

There are only few minor differences between both that
are handled by that function, driven by the ts->inidle
cpu variable and the inidle parameter. The whole guarantees
that we only update the dyntick mode on irq exit if we actually
interrupted the dyntick idle mode, and that we enter in RCU extended
quiescent state from idle loop entry only.

Split this function into:

- tick_nohz_idle_enter(), which sets ts->inidle to 1, enters
dynticks idle mode unconditionally if it can, and enters into RCU
extended quiescent state.

- tick_nohz_irq_exit() which only updates the dynticks idle mode
when ts->inidle is set (ie: if tick_nohz_idle_enter() has been called).

To maintain symmetry, tick_nohz_restart_sched_tick() has been renamed
into tick_nohz_idle_exit().

This simplifies the code and micro-optimize the irq exit path (no need
for local_irq_save there). This also prepares for the split between
dynticks and rcu extended quiescent state logics. We'll need this split to
further fix illegal uses of RCU in extended quiescent states in the idle
loop.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Previous patches allow the NMI subsystem to process multipe NMI events
in one NMI.  As previously discussed this can cause issues when an event
triggered another NMI but is processed in the current NMI.  This causes the
next NMI to go unprocessed and become an 'unknown' NMI.

To handle this, we first have to flag whether or not the NMI handler handled
more than one event or not.  If it did, then there exists a chance that
the next NMI might be already processed.  Once the NMI is flagged as a
candidate to be swallowed, we next look for a back-to-back NMI condition.

This is determined by looking at the %rip from pt_regs.  If it is the same
as the previous NMI, it is assumed the cpu did not have a chance to jump
back into a non-NMI context and execute code and instead handled another NMI.

If both of those conditions are true then we will swallow any unknown NMI.

There still exists a chance that we accidentally swallow a real unknown NMI,
but for now things seem better.

An optimization has also been added to the nmi notifier rountine.  Because x86
can latch up to one NMI while currently processing an NMI, we don't have to
worry about executing _all_ the handlers in a standalone NMI.  The idea is
if multiple NMIs come in, the second NMI will represent them.  For those
back-to-back NMI cases, we have the potentail to drop NMIs.  Therefore only
execute all the handlers in the second half of a detected back-to-back NMI.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317409584-23662-5-git-send-email-dzickus@redhat.comSigned-off-by: Ingo Molnar <mingo@elte.hu>

This patch fixes the typo in parameters passed to
x86_32 switch_to() description.
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

cpuidle users should call cpuidle_call_idle() directly
rather than via (pm_idle)() function pointer.

Architecture may choose to continue using (pm_idle)(),
but cpuidle need not depend on it:

  my_arch_cpu_idle()
	...
	if(cpuidle_call_idle())
		pm_idle();

cc: Kevin Hilman <khilman@deeprootsystems.com>
cc: Paul Mundt <lethal@linux-sh.org>
cc: x86@kernel.org
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

Unconditionally changing the address limit to USER_DS and not restoring
it to its old value in the error path is wrong because it prevents us
using kernel memory on repeated calls to this function.  This, in fact,
breaks the fallback of hard coded paths to the init program from being
ever successful if the first candidate fails to load.

With this patch applied switching to USER_DS is delayed until the point
of no return is reached which makes it possible to have a multi-arch
rootfs with one arch specific init binary for each of the (hard coded)
probed paths.

Since the address limit is already set to USER_DS when start_thread()
will be invoked, this redundancy can be safely removed.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

cpuidle/x86/perf: fix power:cpu_idle double end events and throw cpu_idle events from the cpuidle layer

Currently intel_idle and acpi_idle driver show double cpu_idle "exit idle"
events -> this patch fixes it and makes cpu_idle events throwing less complex.

It also introduces cpu_idle events for all architectures which use
the cpuidle subsystem, namely:
  - arch/arm/mach-at91/cpuidle.c
  - arch/arm/mach-davinci/cpuidle.c
  - arch/arm/mach-kirkwood/cpuidle.c
  - arch/arm/mach-omap2/cpuidle34xx.c
  - arch/drivers/acpi/processor_idle.c (for all cases, not only mwait)
  - arch/x86/kernel/process.c (did throw events before, but was a mess)
  - drivers/idle/intel_idle.c (did throw events before)

Convention should be:
Fire cpu_idle events inside the current pm_idle function (not somewhere
down the the callee tree) to keep things easy.

Current possible pm_idle functions in X86:
c1e_idle, poll_idle, cpuidle_idle_call, mwait_idle, default_idle
-> this is really easy is now.

This affects userspace:
The type field of the cpu_idle power event can now direclty get
mapped to:
/sys/devices/system/cpu/cpuX/cpuidle/stateX/{name,desc,usage,time,...}
instead of throwing very CPU/mwait specific values.
This change is not visible for the intel_idle driver.
For the acpi_idle driver it should only be visible if the vendor
misses out C-states in his BIOS.
Another (perf timechart) patch reads out cpuidle info of cpu_idle
events from:
/sys/.../cpuidle/stateX/*, then the cpuidle events are mapped
to the correct C-/cpuidle state again, even if e.g. vendors miss
out C-states in their BIOS and for example only export C1 and C3.
-> everything is fine.
Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: Robert Schoene <robert.schoene@tu-dresden.de>
CC: Jean Pihet <j-pihet@ti.com>
CC: Arjan van de Ven <arjan@linux.intel.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: linux-pm@lists.linux-foundation.org
CC: linux-acpi@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: linux-perf-users@vger.kernel.org
CC: linux-omap@vger.kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>

Add these new power trace events:

 power:cpu_idle
 power:cpu_frequency
 power:machine_suspend

The old C-state/idle accounting events:
  power:power_start
  power:power_end

Have now a replacement (but we are still keeping the old
tracepoints for compatibility):

  power:cpu_idle

and
  power:power_frequency

is replaced with:
  power:cpu_frequency

power:machine_suspend is newly introduced.

Jean Pihet has a patch integrated into the generic layer
(kernel/power/suspend.c) which will make use of it.

the type= field got removed from both, it was never
used and the type is differed by the event type itself.

perf timechart userspace tool gets adjusted in a separate patch.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Jean Pihet <jean.pihet@newoldbits.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: rjw@sisk.pl
LKML-Reference: <1294073445-14812-3-git-send-email-trenn@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <1290072314-31155-2-git-send-email-trenn@suse.de>

Systems using the idle thread from process_32.c and process_64.c
do not generate power_end events which could be traced using
perf. This patch adds the event generation for such systems.
Signed-off-by: Robert Schoene <robert.schoene@tu-dresden.de>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1276515440.5441.45.camel@localhost>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Currently all fpu state access is through tsk->thread.xstate.  Since we wish
to generalize fpu access to non-task contexts, wrap the state in a new
'struct fpu' and convert existing access to use an fpu API.

Signal frame handlers are not converted to the API since they will remain
task context only things.
Signed-off-by: Avi Kivity <avi@redhat.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1273135546-29690-3-git-send-email-avi@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Support for the PMU's BTS features has been upstreamed in
v2.6.32, but we still have the old and disabled ptrace-BTS,
as Linus noticed it not so long ago.

It's buggy: TIF_DEBUGCTLMSR is trampling all over that MSR without
regard for other uses (perf) and doesn't provide the flexibility
needed for perf either.

Its users are ptrace-block-step and ptrace-bts, since ptrace-bts
was never used and ptrace-block-step can be implemented using a
much simpler approach.

So axe all 3000 lines of it. That includes the *locked_memory*()
APIs in mm/mlock.c as well.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Markus Metzger <markus.t.metzger@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20100325135413.938004390@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Using kernel_stack_pointer() allows 32-bit and 64-bit versions to
be merged.  This is more correct for 64-bit, since the old %rsp is
always saved on the stack.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1263397555-27695-1-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Andrew Morton reported a strange looking kmemcheck warning:

  WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (ffff88004fba6c20)
  0000000000000000310000000000000000000000000000002413000000c9ffff
   u u u u u u u u u u u u u u u u i i i i i i i i u u u u u u u u

   [<ffffffff810af3aa>] kmemleak_scan+0x25a/0x540
   [<ffffffff810afbcb>] kmemleak_scan_thread+0x5b/0xe0
   [<ffffffff8104d0fe>] kthread+0x9e/0xb0
   [<ffffffff81003074>] kernel_thread_helper+0x4/0x10
   [<ffffffffffffffff>] 0xffffffffffffffff

The above printout is missing register dump completely. The
problem here is that the output comes from syslog which doesn't
show KERN_INFO log-level messages. We didn't see this before
because both of us were testing on 32-bit kernels which use the
_default_ log-level.

Fix that up by explicitly using KERN_DEFAULT log-level for
__show_regs() printks.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1261988819.4641.2.camel@penberg-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260380084-3707-6-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260380084-3707-5-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

The arg should be in %eax, but that is clobbered by the return value
of clone.  The function pointer can be in any register.  Also, don't
push args onto the stack, since regparm(3) is the normal calling
convention now.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260380084-3707-4-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Change 32-bit sys_clone to new PTREGSCALL stub, and merge with 64-bit.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260403316-5679-7-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Change 32-bit sys_execve to PTREGSCALL3, and merge with 64-bit.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260403316-5679-4-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Unify x86_32 and x86_64 implementations of __show_regs() header,
standardizing on the x86_64 format string in the process. Also,
32-bit will now call print_modules.
Signed-off-by: Andy Isaacson <adi@hexapodia.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Robert Hancock <hancockrwd@gmail.com>
Cc: Richard Zidlicky <rz@linux-m68k.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20091208082942.GA27174@hexapodia.org>
[ v2: resolved conflict ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

This patch rebase the implementation of the breakpoints API on top of
perf events instances.

Each breakpoints are now perf events that handle the
register scheduling, thread/cpu attachment, etc..

The new layering is now made as follows:

       ptrace       kgdb      ftrace   perf syscall
          \          |          /         /
           \         |         /         /
                                        /
            Core breakpoint API        /
                                      /
                     |               /
                     |              /

              Breakpoints perf events

                     |
                     |

               Breakpoints PMU ---- Debug Register constraints handling
                                    (Part of core breakpoint API)
                     |
                     |

             Hardware debug registers

Reasons of this rewrite:

- Use the centralized/optimized pmu registers scheduling,
  implying an easier arch integration
- More powerful register handling: perf attributes (pinned/flexible
  events, exclusive/non-exclusive, tunable period, etc...)

Impact:

- New perf ABI: the hardware breakpoints counters
- Ptrace breakpoints setting remains tricky and still needs some per
  thread breakpoints references.

Todo (in the order):

- Support breakpoints perf counter events for perf tools (ie: implement
  perf_bpcounter_event())
- Support from perf tools

Changes in v2:

- Follow the perf "event " rename
- The ptrace regression have been fixed (ptrace breakpoint perf events
  weren't released when a task ended)
- Drop the struct hw_breakpoint and store generic fields in
  perf_event_attr.
- Separate core and arch specific headers, drop
  asm-generic/hw_breakpoint.h and create linux/hw_breakpoint.h
- Use new generic len/type for breakpoint
- Handle off case: when breakpoints api is not supported by an arch

Changes in v3:

- Fix broken CONFIG_KVM, we need to propagate the breakpoint api
  changes to kvm when we exit the guest and restore the bp registers
  to the host.

Changes in v4:

- Drop the hw_breakpoint_restore() stub as it is only used by KVM
- EXPORT_SYMBOL_GPL hw_breakpoint_restore() as KVM can be built as a
  module
- Restore the breakpoints unconditionally on kvm guest exit:
  TIF_DEBUG_THREAD doesn't anymore cover every cases of running
  breakpoints and vcpu->arch.switch_db_regs might not always be
  set when the guest used debug registers.
  (Waiting for a reliable optimization)

Changes in v5:

- Split-up the asm-generic/hw-breakpoint.h moving to
  linux/hw_breakpoint.h into a separate patch
- Optimize the breakpoints restoring while switching from kvm guest
  to host. We only want to restore the state if we have active
  breakpoints to the host, otherwise we don't care about messed-up
  address registers.
- Add asm/hw_breakpoint.h to Kbuild
- Fix bad breakpoint type in trace_selftest.c

Changes in v6:

- Fix wrong header inclusion in trace.h (triggered a build
  error with CONFIG_FTRACE_SELFTEST
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jan Kiszka <jan.kiszka@web.de>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>

show_regs() is called as a mini BUG() equivalent in some places,
specifically for the "scheduling while atomic" case.

Unfortunately right now it does not print a Code: line unlike
a real bug/oops.

This patch changes the x86 implementation of show_regs() so that
it calls the same function as oopses do to print the registers
as well as the Code: line.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20091102165915.4a980fc0@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The way to obtain a kernel-mode stack pointer from a struct pt_regs in
32-bit mode is "subtle": the stack doesn't actually contain the stack
pointer, but rather the location where it would have been marks the
actual previous stack frame.  For clarity, use kernel_stack_pointer()
instead of coding this weirdness explicitly.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

On x86_64, percpu variables current_task and kernel_stack are used for
get_current() and current_thread_info() respectively and thus are
often used close to each other.  Move definition of current_task to
kernel/cpu/common.c right above kernel_stack definition and align it
to cacheline so that they always fall into the same cacheline.  Two
percpu variables defined there together - irq_stack_ptr and irq_count
- are also pretty hot and will benefit from sharing the cacheline.

For consistency, current_task definition for x86_32 is also moved to
kernel/cpu/common.c.

Putting current_task and kernel_stack into the same cacheline was
suggested by Linus Torvalds.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

If we're preloading the fpu state during context switch, make sure the clts
happens while we're batching the cpu context update, then do the actual
__math_state_restore once the updates are flushed.

This allows more efficient context switches when running paravirtualized,
as all the hypercalls can be folded together into one.

[ Impact: optimise paravirtual FPU context switch ]
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>

This patch enables the use of abstract debug registers in
process-handling routines, according to the new hardware breakpoint
Api.

[ Impact: adapt thread breakpoints handling code to the new breakpoint Api ]
Original-patch-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

<stdarg.h> is not needed by these files, remove them.

[ Impact: cleanup ]
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: akpm@linux-foundation.org
LKML-Reference: <20090512032956.5040.77055.sendpatchset@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Merge arch_align_stack() and arch_randomize_brk(), since
they are the same.

Tested on x86_64.

[ Impact: cleanup ]
Signed-off-by: Amerigo Wang <amwang@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Add a warning in case a debug store context is not removed before
the task it is attached to is freed.

Remove the old warning at thread exit. It is too early.

Declare the debug store context field in thread_struct unconditionally.

Remove ds_copy_thread() and ds_exit_thread() and do the work directly
in process*.c.
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: oleg@redhat.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144601.254472000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

First argument unused since 2.3.11.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Impact: fix lazy context switch API

Pass the previous and next tasks into the context switch start
end calls, so that the called functions can properly access the
task state (esp in end_context_switch, in which the next task
is not yet completely current).
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

Impact: simplification, prepare for later changes

Make lazy cpu mode more specific to context switching, so that
it makes sense to do more context-switch specific things in
the callbacks.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

With x86-32 and -64 using the same mechanism for managing the
tss io permissions bitmap, large chunks of process*.c are
trivially unifyable, including:

 - exit_thread
 - flush_thread
 - __switch_to_xtra (along with tsc enable/disable)

and as bonus pickups:

 - sys_fork
 - sys_vfork

(Note: asmlinkage expands to empty on x86-64)
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Impact: remove 32-bit optimization to prepare unification

x86-32 and -64 differ in the way they context-switch tasks
with io permission bitmaps.  x86-64 simply copies the next
tasks io bitmap into place (if any) on context switch.  x86-32
invalidates the bitmap on context switch, so that the next
IO instruction will fault; at that point it installs the
appropriate IO bitmap.

This makes context switching IO-bitmap-using tasks a bit more
less expensive, at the cost of making the next IO instruction
slower due to the extra fault.  This tradeoff only makes sense
if IO-bitmap-using processes are relatively common, but they
don't actually use IO instructions very often.

However, in a typical desktop system, the only process likely
to be using IO bitmaps is the X server, and nothing at all on
a server.  Therefore the lazy context switch doesn't really win
all that much, and its just a gratuitious difference from
64-bit code.

This patch removes the lazy context switch, with a view to
unifying this code in a later change.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Damien Wyart reported high ksoftirqd CPU usage (20%) on an
otherwise idle system.

The function-graph trace Damien provided:

>   799.521187 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.521371 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.521555 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.521738 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.521934 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.522068 |   1)  ksoftir-2324  |               |                rcu_check_callbacks() {
>   799.522208 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.522392 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.522575 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.522759 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.522956 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.523074 |   1)  ksoftir-2324  |               |                  rcu_check_callbacks() {
>   799.523214 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.523397 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.523579 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.523762 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.523960 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.524079 |   1)  ksoftir-2324  |               |                  rcu_check_callbacks() {
>   799.524220 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.524403 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.524587 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
>   799.524770 |   1)    <idle>-0    |               |  rcu_check_callbacks() {
> [ . . . ]

Shows rcu_check_callbacks() being invoked way too often. It should be called
once per jiffy, and here it is called no less than 22 times in about
3.5 milliseconds, meaning one call every 160 microseconds or so.

Why do we need to call rcu_pending() and rcu_check_callbacks() from the
idle loop of 32-bit x86, especially given that no other architecture does
this?

The following patch removes the call to rcu_pending() and
rcu_check_callbacks() from the x86 32-bit idle loop in order to
reduce the softirq load on idle systems.
Reported-by: Damien Wyart <damien.wyart@free.fr>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Some syscalls need to access the pt_regs structure, either to copy
user register state or to modifiy it.  This patch adds stubs to load
the address of the pt_regs struct into the %eax register, and changes
the syscalls to take the pointer as an argument instead of relying on
the assumption that the pt_regs structure overlaps the function
arguments.

Drop the use of regparm(1) due to concern about gcc bugs, and to move
in the direction of the eventual removal of regparm(0) for asmlinkage.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

Some syscalls need to access the pt_regs structure, either to copy
user register state or to modifiy it.  This patch adds stubs to load
the address of the pt_regs struct into the %eax register, and changes
the syscalls to regparm(1) to receive the pt_regs pointer as the
first argument.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Impact: fix x86_32 stack protector

Brian Gerst found out that %gs was being initialized to stack_canary
instead of stack_canary - 20, which basically gave the same canary
value for all threads.  Fixing this also exposed the following bugs.

* cpu_idle() didn't call boot_init_stack_canary()

* stack canary switching in switch_to() was being done too late making
  the initial run of a new thread use the old stack canary value.

Fix all of them and while at it update comment in cpu_idle() about
calling boot_init_stack_canary().
Reported-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Impact: stack protector for x86_32

Implement stack protector for x86_32.  GDT entry 28 is used for it.
It's set to point to stack_canary-20 and have the length of 24 bytes.
CONFIG_CC_STACKPROTECTOR turns off CONFIG_X86_32_LAZY_GS and sets %gs
to the stack canary segment on entry.  As %gs is otherwise unused by
the kernel, the canary can be anywhere.  It's defined as a percpu
variable.

x86_32 exception handlers take register frame on stack directly as
struct pt_regs.  With -fstack-protector turned on, gcc copies the
whole structure after the stack canary and (of course) doesn't copy
back on return thus losing all changed.  For now, -fno-stack-protector
is added to all files which contain those functions.  We definitely
need something better.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Impact: pt_regs changed, lazy gs handling made optional, add slight
        overhead to SAVE_ALL, simplifies error_code path a bit

On x86_32, %gs hasn't been used by kernel and handled lazily.  pt_regs
doesn't have place for it and gs is saved/loaded only when necessary.
In preparation for stack protector support, this patch makes lazy %gs
handling optional by doing the followings.

* Add CONFIG_X86_32_LAZY_GS and place for gs in pt_regs.

* Save and restore %gs along with other registers in entry_32.S unless
  LAZY_GS.  Note that this unfortunately adds "pushl $0" on SAVE_ALL
  even when LAZY_GS.  However, it adds no overhead to common exit path
  and simplifies entry path with error code.

* Define different user_gs accessors depending on LAZY_GS and add
  lazy_save_gs() and lazy_load_gs() which are noop if !LAZY_GS.  The
  lazy_*_gs() ops are used to save, load and clear %gs lazily.

* Define ELF_CORE_COPY_KERNEL_REGS() which always read %gs directly.

xen and lguest changes need to be verified.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>