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perf: Avoid RCU vs preemption assumptions

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The per-pmu per-cpu context patch converted things from
get_cpu_var() to this_cpu_ptr(), but that only works if
rcu_read_lock() actually disables preemption, and since
there is no such guarantee, we need to fix that.

Use the newly introduced {get,put}_cpu_ptr().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
LKML-Reference: <20100917093009.308453028@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-09-16 19:17:24 +02:00 committed by Ingo Molnar
parent 8b8e2ec1ee
commit 41945f6ccf
1 changed files with 12 additions and 6 deletions
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18
kernel/perf_event.c
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@ -3836,18 +3836,20 @@ static void perf_event_task_event(struct perf_task_event *task_event)
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
perf_event_task_ctx(&cpuctx->ctx, task_event);
ctx = task_event->task_ctx;
if (!ctx) {
ctxn = pmu->task_ctx_nr;
if (ctxn < 0)
continue;
goto next;
ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
}
if (ctx)
perf_event_task_ctx(ctx, task_event);
next:
put_cpu_ptr(pmu->pmu_cpu_context);
}
rcu_read_unlock();
}
@ -3969,16 +3971,18 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
perf_event_comm_ctx(&cpuctx->ctx, comm_event);
ctxn = pmu->task_ctx_nr;
if (ctxn < 0)
continue;
goto next;
ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
if (ctx)
perf_event_comm_ctx(ctx, comm_event);
next:
put_cpu_ptr(pmu->pmu_cpu_context);
}
rcu_read_unlock();
}
@ -4152,19 +4156,21 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
perf_event_mmap_ctx(&cpuctx->ctx, mmap_event,
vma->vm_flags & VM_EXEC);
ctxn = pmu->task_ctx_nr;
if (ctxn < 0)
continue;
goto next;
ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
if (ctx) {
perf_event_mmap_ctx(ctx, mmap_event,
vma->vm_flags & VM_EXEC);
}
next:
put_cpu_ptr(pmu->pmu_cpu_context);
}
rcu_read_unlock();