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perf_counter: Fix cpuctx->task_ctx races 

Peter noticed that we are sometimes reading cpuctx->task_ctx with
interrupts enabled.

Noticed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2009-05-29 11:25:09 +02:00
parent ad3a37de81
commit 3f4dee2273
1 changed files with 20 additions and 8 deletions
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28
kernel/perf_counter.c
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@ -234,15 +234,18 @@ static void __perf_counter_remove_from_context(void *info)
struct perf_counter_context *ctx = counter->ctx;
unsigned long flags;
local_irq_save(flags);
/*
* If this is a task context, we need to check whether it is
* the current task context of this cpu. If not it has been
* scheduled out before the smp call arrived.
*/
if (ctx->task && cpuctx->task_ctx != ctx)
if (ctx->task && cpuctx->task_ctx != ctx) {
local_irq_restore(flags);
return;
}
spin_lock_irqsave(&ctx->lock, flags);
spin_lock(&ctx->lock);
/*
* Protect the list operation against NMI by disabling the
* counters on a global level.
@ -382,14 +385,17 @@ static void __perf_counter_disable(void *info)
struct perf_counter_context *ctx = counter->ctx;
unsigned long flags;
local_irq_save(flags);
/*
* If this is a per-task counter, need to check whether this
* counter's task is the current task on this cpu.
*/
if (ctx->task && cpuctx->task_ctx != ctx)
if (ctx->task && cpuctx->task_ctx != ctx) {
local_irq_restore(flags);
return;
}
spin_lock_irqsave(&ctx->lock, flags);
spin_lock(&ctx->lock);
/*
* If the counter is on, turn it off.
@ -615,6 +621,7 @@ static void __perf_install_in_context(void *info)
unsigned long flags;
int err;
local_irq_save(flags);
/*
* If this is a task context, we need to check whether it is
* the current task context of this cpu. If not it has been
@ -623,12 +630,14 @@ static void __perf_install_in_context(void *info)
* on this cpu because it had no counters.
*/
if (ctx->task && cpuctx->task_ctx != ctx) {
if (cpuctx->task_ctx || ctx->task != current)
if (cpuctx->task_ctx || ctx->task != current) {
local_irq_restore(flags);
return;
}
cpuctx->task_ctx = ctx;
}
spin_lock_irqsave(&ctx->lock, flags);
spin_lock(&ctx->lock);
ctx->is_active = 1;
update_context_time(ctx);
@ -745,17 +754,20 @@ static void __perf_counter_enable(void *info)
unsigned long flags;
int err;
local_irq_save(flags);
/*
* If this is a per-task counter, need to check whether this
* counter's task is the current task on this cpu.
*/
if (ctx->task && cpuctx->task_ctx != ctx) {
if (cpuctx->task_ctx || ctx->task != current)
if (cpuctx->task_ctx || ctx->task != current) {
local_irq_restore(flags);
return;
}
cpuctx->task_ctx = ctx;
}
spin_lock_irqsave(&ctx->lock, flags);
spin_lock(&ctx->lock);
ctx->is_active = 1;
update_context_time(ctx);