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Commit b58f6b0d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf, core: Fix initial task_ctx/event installation 



A lost Quilt refresh of 2c29ef0f (perf: Simplify and fix
__perf_install_in_context()) is causing grief and lockups,
reported by Jiri Olsa.

When installing an event in a task context, there's a number of
issues:

 - there might not be an existing task context, in which case
   we should install the now current context;

 - there might already be a context, not the current one, in
   which case we should de-schedule the old and install the new;

these cases were dealt with in the lost refresh, however there is one
further case that was found in testing:

 - there might already be a context, the current one, in which
   case we should still de-schedule, and should take care
   to re-install it (note that task_ctx_sched_out() clears
   cpuctx->task_ctx).

Reported-by: default avatarJiri Olsa <jolsa@redhat.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1307399008.2497.971.camel@laptop


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3ce2a0bc

kernel/events/core.c

+17 −11
Original line number Original line Diff line number Diff line
@@ -1505,25 +1505,31 @@ static int __perf_install_in_context(void *info) 
	struct perf_event_context *task_ctx = cpuctx->task_ctx;

	struct perf_event_context *task_ctx = cpuctx->task_ctx;

	struct task_struct *task = current;

	struct task_struct *task = current;





	perf_ctx_lock(cpuctx, cpuctx->task_ctx);

	perf_ctx_lock(cpuctx, task_ctx);

	perf_pmu_disable(cpuctx->ctx.pmu);

	perf_pmu_disable(cpuctx->ctx.pmu);





	/*

	/*

	 * If there was an active task_ctx schedule it out.

	 * If there was an active task_ctx schedule it out.

	 */

	 */

	if (task_ctx) {

	if (task_ctx)

		task_ctx_sched_out(task_ctx);

		task_ctx_sched_out(task_ctx);



	/*

	/*

	 * If the context we're installing events in is not the

	 * If the context we're installing events in is not the

	 * active task_ctx, flip them.

	 * active task_ctx, flip them.

	 */

	 */

	if (ctx->task && task_ctx != ctx) {

	if (ctx->task && task_ctx != ctx) {

			raw_spin_unlock(&cpuctx->ctx.lock);

		if (task_ctx)

			raw_spin_unlock(&task_ctx->lock);

		raw_spin_lock(&ctx->lock);

		raw_spin_lock(&ctx->lock);

			cpuctx->task_ctx = task_ctx = ctx;

		task_ctx = ctx;

	}

	}



	if (task_ctx) {

		cpuctx->task_ctx = task_ctx;

		task = task_ctx->task;

		task = task_ctx->task;

	}

	}



	cpu_ctx_sched_out(cpuctx, EVENT_ALL);

	cpu_ctx_sched_out(cpuctx, EVENT_ALL);





	update_context_time(ctx);

	update_context_time(ctx);