Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 41945f6c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf: Avoid RCU vs preemption assumptions 



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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
LKML-Reference: <20100917093009.308453028@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8b8e2ec1

kernel/perf_event.c

+12 −6
Original line number Diff line number Diff line
@@ -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();