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Commit cca20946 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf/core: Fix event_function_local() 



Vincent reported triggering the WARN_ON_ONCE() in event_function_local().

While thinking through cases I noticed that by using event_function()
directly, we miss the inactive case usually handled by
event_function_call().

Therefore construct a blend of event_function_call() and
event_function() that handles the cases relevant to
event_function_local().

Reported-by: default avatarVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # 4.5+
Fixes: fae3fde6 ("perf: Collapse and fix event_function_call() users")
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 6c4687cc

kernel/events/core.c

+48 −12
Original line number Diff line number Diff line
@@ -242,18 +242,6 @@ static int event_function(void *info) 
	return ret;

}



static void event_function_local(struct perf_event *event, event_f func, void *data)

{

	struct event_function_struct efs = {

		.event = event,

		.func = func,

		.data = data,

	};



	int ret = event_function(&efs);

	WARN_ON_ONCE(ret);

}



static void event_function_call(struct perf_event *event, event_f func, void *data)

{

	struct perf_event_context *ctx = event->ctx;
@@ -303,6 +291,54 @@ static void event_function_call(struct perf_event *event, event_f func, void *da 
	raw_spin_unlock_irq(&ctx->lock);

}



/*

 * Similar to event_function_call() + event_function(), but hard assumes IRQs

 * are already disabled and we're on the right CPU.

 */

static void event_function_local(struct perf_event *event, event_f func, void *data)

{

	struct perf_event_context *ctx = event->ctx;

	struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

	struct task_struct *task = READ_ONCE(ctx->task);

	struct perf_event_context *task_ctx = NULL;



	WARN_ON_ONCE(!irqs_disabled());



	if (task) {

		if (task == TASK_TOMBSTONE)

			return;



		task_ctx = ctx;

	}



	perf_ctx_lock(cpuctx, task_ctx);



	task = ctx->task;

	if (task == TASK_TOMBSTONE)

		goto unlock;



	if (task) {

		/*

		 * We must be either inactive or active and the right task,

		 * otherwise we're screwed, since we cannot IPI to somewhere

		 * else.

		 */

		if (ctx->is_active) {

			if (WARN_ON_ONCE(task != current))

				goto unlock;



			if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))

				goto unlock;

		}

	} else {

		WARN_ON_ONCE(&cpuctx->ctx != ctx);

	}



	func(event, cpuctx, ctx, data);

unlock:

	perf_ctx_unlock(cpuctx, task_ctx);

}



#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\

		       PERF_FLAG_FD_OUTPUT  |\

		       PERF_FLAG_PID_CGROUP |\