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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>
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Impact: cleanup
Fix:
WARNING: Use #include <linux/uaccess.h> instead of <asm/uaccess.h>
WARNING: Use #include <linux/io.h> instead of <asm/io.h>
WARNING: Use #include <linux/kdebug.h> instead of <asm/kdebug.h>
WARNING: Use #include <linux/smp.h> instead of <asm/smp.h>
ERROR: "foo * bar" should be "foo *bar"
ERROR: trailing whitespace
ERROR: spaces required around that ':' (ctx:WxO)
ERROR: spaces required around that ':' (ctx:OxW)
total: 7 errors, 4 warnings
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Impact: introduce new ptrace facility
Add arch_ptrace_untrace() function that is called when the tracer
detaches (either voluntarily or when the tracing task dies);
ptrace_disable() is only called on a voluntary detach.
Add ptrace_fork() and arch_ptrace_fork(). They are called when a
traced task is forked.
Clear DS and BTS related fields on fork.
Release DS resources and reclaim memory in ptrace_untrace(). This
releases resources already when the tracing task dies. We used to do
that when the traced task dies.
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Impact: cleanup
Move the BTS bits from ptrace.c into ds.c.
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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special functions
Impact: trace more functions
When the function graph tracer is configured, three more files are not
traced to prevent only four functions to be traced. And this impacts the
normal function tracer too.
arch/x86/kernel/process_64/32.c:
I had crashes when I let this file traced. After some debugging, I saw
that the "current" task point was changed inside__swtich_to(), ie:
"write_pda(pcurrent, next_p);" inside process_64.c Since the tracer store
the original return address of the function inside current, we had
crashes. Only __switch_to() has to be excluded from tracing.
kernel/module.c and kernel/extable.c:
Because of a function used internally by the function graph tracer:
__kernel_text_address()
To let the other functions inside these files to be traced, this patch
introduces the __notrace_funcgraph function prefix which is __notrace if
function graph tracer is configured and nothing if not.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Currently the low-level function to dump user-passed registers on i386 is
called __show_registers() whereas on x86-64 it's called __show_regs(). Unify
the API to simplify porting of kmemcheck to x86-64.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
arch/x86/kernel/cpu/common.c
arch/x86/kernel/process_64.c
arch/x86/xen/enlighten.c
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'x86/crashdump', 'x86/debug', 'x86/defconfig', 'x86/doc', 'x86/exports', 'x86/fpu', 'x86/gart', 'x86/idle', 'x86/mm', 'x86/mtrr', 'x86/nmi-watchdog', 'x86/oprofile', 'x86/paravirt', 'x86/reboot', 'x86/sparse-fixes', 'x86/tsc', 'x86/urgent' and 'x86/vmalloc' into x86-v28-for-linus-phase1
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Conflicts:
arch/x86/kernel/process_32.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
include/asm-x86/ds.h
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Fix build error introduced by commit 4faac97d44ac27 ("x86: prevent stale
state of c1e_mask across CPU offline/online").
process_32.c needs to include idle.h to get the prototype for
c1e_remove_cpu()
Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Impact: hang which happens across CPU offline/online on AMD C1E systems.
When a CPU goes offline then the corresponding bit in the broadcast
mask is cleared. For AMD C1E enabled CPUs we do not reenable the
broadcast when the CPU comes online again as we do not clear the
corresponding bit in the c1e_mask, which keeps track which CPUs
have been switched to broadcast already. So on those !$@#& machines
we never switch back to broadcasting after a CPU offline/online cycle.
Clear the bit when the CPU plays dead.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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in order to diagnose hard system specific issues, it's useful to
have the system name in the oops (as provided by DMI)
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Move reset_lazy_tlbstate into tlb_32.c, and define noop versions of
play_dead() in process_{32,64}.c when !CONFIG_SMP.
Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Add the new play_dead into smpboot.c, as it fits more cleanly in there
alongside other CONFIG_HOTPLUG functions.
Separate out the common code into its own function.
Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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The removal of the CPU from the various maps was redundant as it already
happened in cpu_disable.
After cleaning this up, cpu_uninit only resets the tlb state, so rename
it and create a noop version for the X86_64 case (so the two play_deads
can be unified later).
Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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When a CPU core is shut down, all of its caches need to be flushed
to prevent stale data from causing errors if the core is resumed.
Current Linux suspend code performs an assignment after the flush,
which can add dirty data back to the cache. On some AMD platforms,
additional speculative reads have caused crashes on resume because
of this dirty data.
Relocate the cache flush to be the very last thing done before
halting. Tie into an assembly line so the compile will not
reorder it. Add some documentation explaining what is going
on and why we're doing this.
Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
Acked-by: Mark Borden <mark.borden@amd.com>
Acked-by: Michael Hohmuth <michael.hohmuth@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
include/asm-x86/dma-mapping.h
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
arch/x86/Kconfig.cpu
arch/x86/kernel/cpu/intel.c
arch/x86/kernel/setup_64.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Moved DECLARE_PER_CPU(int, cpu_number) from CONFIG_X86_32_SMP to CONFIG_X86_32
because cpu_number is required for both.
And include asm/smp.h in process_32.c
Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
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Declaring arch-dependent syscalls for x86 architecture
Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
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Jack Ren and Eric Miao tracked down the following long standing
problem in the NOHZ code:
scheduler switch to idle task
enable interrupts
Window starts here
----> interrupt happens (does not set NEED_RESCHED)
irq_exit() stops the tick
----> interrupt happens (does set NEED_RESCHED)
return from schedule()
cpu_idle(): preempt_disable();
Window ends here
The interrupts can happen at any point inside the race window. The
first interrupt stops the tick, the second one causes the scheduler to
rerun and switch away from idle again and we end up with the tick
disabled.
The fact that it needs two interrupts where the first one does not set
NEED_RESCHED and the second one does made the bug obscure and extremly
hard to reproduce and analyse. Kudos to Jack and Eric.
Solution: Limit the NOHZ functionality to the idle loop to make sure
that we can not run into such a situation ever again.
cpu_idle()
{
preempt_disable();
while(1) {
tick_nohz_stop_sched_tick(1); <- tell NOHZ code that we
are in the idle loop
while (!need_resched())
halt();
tick_nohz_restart_sched_tick(); <- disables NOHZ mode
preempt_enable_no_resched();
schedule();
preempt_disable();
}
}
In hindsight we should have done this forever, but ...
/me grabs a large brown paperbag.
Debugged-by: Jack Ren <jack.ren@marvell.com>,
Debugged-by: eric miao <eric.y.miao@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Conflicts:
arch/x86/kernel/entry_32.S
arch/x86/kernel/process_32.c
arch/x86/kernel/process_64.c
arch/x86/lib/Makefile
include/asm-x86/irqflags.h
kernel/Makefile
kernel/sched.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Take it out of smpboot.c, and move it to process_32.c, closer
to its only user.
Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Patrick McHardy reported a crash:
> > I get this oops once a day, its apparently triggered by something
> > run by cron, but the process is a different one each time.
> >
> > Kernel is -git from yesterday shortly before the -rc6 release
> > (last commit is the usb-2.6 merge, the x86 patches are missing),
> > .config is attached.
> >
> > I'll retry with current -git, but the patches that have gone in
> > since I last updated don't look related.
> >
> > [62060.043009] BUG: unable to handle kernel NULL pointer dereference at
> > 000001ff
> > [62060.043009] IP: [<c0102a9b>] __switch_to+0x2f/0x118
> > [62060.043009] *pde = 00000000
> > [62060.043009] Oops: 0002 [#1] PREEMPT
Vegard Nossum analyzed it:
> This decodes to
>
> 0: 0f ae 00 fxsave (%eax)
>
> so it's related to the floating-point context. This is the exact
> location of the crash:
>
> $ addr2line -e arch/x86/kernel/process_32.o -i ab0
> include/asm/i387.h:232
> include/asm/i387.h:262
> arch/x86/kernel/process_32.c:595
>
> ...so it looks like prev_task->thread.xstate->fxsave has become NULL.
> Or maybe it never had any other value.
Somehow (as described below) TS_USEDFPU is set but the fpu is not
allocated or freed.
Another possible FPU pre-emption issue with the sleazy FPU optimization
which was benign before but not so anymore, with the dynamic FPU allocation
patch.
New task is getting exec'd and it is prempted at the below point.
flush_thread() {
...
/*
* Forget coprocessor state..
*/
clear_fpu(tsk);
<----- Preemption point
clear_used_math();
...
}
Now when it context switches in again, as the used_math() is still set
and fpu_counter can be > 5, we will do a math_state_restore() which sets
the task's TS_USEDFPU. After it continues from the above preemption point
it does clear_used_math() and much later free_thread_xstate().
Now, at the next context switch, it is quite possible that xstate is
null, used_math() is not set and TS_USEDFPU is still set. This will
trigger unlazy_fpu() causing kernel oops.
Fix this by clearing tsk's fpu_counter before clearing task's fpu.
Reported-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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more unification. Should cause no change in functionality.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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default_idle is selected in cpu_idle(), when no other idle routine is
selected. Select it in select_idle_routine() when mwait is not
selected.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Jürgen Mell reported an FPU state corruption bug under CONFIG_PREEMPT,
and bisected it to commit v2.6.19-1363-gacc2076, "i386: add sleazy FPU
optimization".
Add tsk_used_math() checks to prevent calling math_state_restore()
which can sleep in the case of !tsk_used_math(). This prevents
making a blocking call in __switch_to().
Apparently "fpu_counter > 5" check is not enough, as in some signal handling
and fork/exec scenarios, fpu_counter > 5 and !tsk_used_math() is possible.
It's a side effect though. This is the failing scenario:
process 'A' in save_i387_ia32() just after clear_used_math()
Got an interrupt and pre-empted out.
At the next context switch to process 'A' again, kernel tries to restore
the math state proactively and sees a fpu_counter > 0 and !tsk_used_math()
This results in init_fpu() during the __switch_to()'s math_state_restore()
And resulting in fpu corruption which will be saved/restored
(save_i387_fxsave and restore_i387_fxsave) during the remaining
part of the signal handling after the context switch.
Bisected-by: Jürgen Mell <j.mell@t-online.de>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Tested-by: Jürgen Mell <j.mell@t-online.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
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Add preempt off timings. A lot of kernel core code is taken from the RT patch
latency trace that was written by Ingo Molnar.
This adds "preemptoff" and "preemptirqsoff" to /debugfs/tracing/available_tracers
Now instead of just tracing irqs off, preemption off can be selected
to be recorded.
When this is selected, it shares the same files as irqs off timings.
One can either trace preemption off, irqs off, or one or the other off.
By echoing "preemptoff" into /debugfs/tracing/current_tracer, recording
of preempt off only is performed. "irqsoff" will only record the time
irqs are disabled, but "preemptirqsoff" will take the total time irqs
or preemption are disabled. Runtime switching of these options is now
supported by simpling echoing in the appropriate trace name into
/debugfs/tracing/current_tracer.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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arch/x86/kernel/process_32.c:566: warning: unused variable 'ds_next'
arch/x86/kernel/process_32.c:566: warning: unused variable 'ds_prev'
Cc: Markus Metzger <markus.t.metzger@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: <juan.villacis@intel.com>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Polish the ds.h interface and add support for PEBS.
Ds.c is meant to be the resource allocator for per-thread and per-cpu
BTS and PEBS recording.
It is used by ptrace/utrace to provide execution tracing of debugged tasks.
It will be used by profilers (e.g. perfmon2).
It may be used by kernel debuggers to provide a kernel execution trace.
Changes in detail:
- guard DS and ptrace by CONFIG macros
- separate DS and BTS more clearly
- simplify field accesses
- add functions to manage PEBS buffers
- add simple protection/allocation mechanism
- added support for Atom
Opens:
- buffer overflow handling
Currently, only circular buffers are supported. This is all we need
for debugging. Profilers would want an overflow notification.
This is planned to be added when perfmon2 is made to use the ds.h
interface.
- utrace intermediate layer
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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OK, so 25-mm1 gave a lockdep error which made me look into this.
The first thing that I noticed was the horrible mess; the second thing I
saw was hacks like: 71e93d15612c61c2e26a169567becf088e71b8ff
The problem is that arch idle routines are somewhat inconsitent with
their IRQ state handling and instead of fixing _that_, we go paper over
the problem.
So the thing I've tried to do is set a standard for idle routines and
fix them all up to adhere to that. So the rules are:
idle routines are entered with IRQs disabled
idle routines will exit with IRQs enabled
Nearly all already did this in one form or another.
Merge the 32 and 64 bit bits so they no longer have different bugs.
As for the actual lockdep warning; __sti_mwait() did a plainly un-annotated
irq-enable.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Only allocate the FPU area when the application actually uses FPU, i.e., in the
first lazy FPU trap. This could save memory for non-fpu using apps.
for example: on my system after boot, there are around 300 processes, with
only 17 using FPU.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Split the FPU save area from the task struct. This allows easy migration
of FPU context, and it's generally cleaner. It also allows the following
two optimizations:
1) only allocate when the application actually uses FPU, so in the first
lazy FPU trap. This could save memory for non-fpu using apps. Next patch
does this lazy allocation.
2) allocate the right size for the actual cpu rather than 512 bytes always.
Patches enabling xsave/xrstor support (coming shortly) will take advantage
of this.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This patch implements the PR_GET_TSC and PR_SET_TSC prctl()
commands on the x86 platform (both 32 and 64 bit.) These
commands control the ability to read the timestamp counter
from userspace (the RDTSC instruction.)
While the RDTSC instuction is a useful profiling tool,
it is also the source of some non-determinism in ring-3.
For deterministic replay applications it is useful to be
able to trap and emulate (and record the outcome of) this
instruction.
This patch uses code earlier used to disable the timestamp
counter for the SECCOMP framework. A side-effect of this
patch is that the SECCOMP environment will now also disable
the timestamp counter on x86_64 due to the addition of the
TIF_NOTSC define on this platform.
The code which enables/disables the RDTSC instruction during
context switches is in the __switch_to_xtra function, which
already handles other unusual conditions, so normal
performance should not have to suffer from this change.
Signed-off-by: Erik Bosman <ejbosman@cs.vu.nl>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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I've made a small investigation about vm86.h inclusion rules and it
looks like everything is more or less ok.
Files that rely on asm/vm86.h symbols are:
- kprobes.c
- process_32.c
- signal_32.c
- traps_32.c
- vm86_32.c
File process_32.c includes vm86.h explicitly. We can remove that
include and it won't break anything.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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This matches x86_64 behaviour, which is a superior one IMHO
Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Otherwise, enabling (or better, subsequent disabling) of single
stepping would cause a kernel oops on CPUs not having this MSR.
The patch could have been added a conditional to the MSR write in
user_disable_single_step(), but centralizing the updates seems safer
and (looking forward) better manageable.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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