Commit 52ba4b0b authored by Like Xu's avatar Like Xu Committed by Paolo Bonzini
Browse files

perf/core: Provide a kernel-internal interface to pause perf_event 



Exporting perf_event_pause() as an external accessor for kernel users (such
as KVM) who may do both disable perf_event and read count with just one
time to hold perf_event_ctx_lock. Also the value could be reset optionally.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarLike Xu <like.xu@linux.intel.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 3ca270fc

include/linux/perf_event.h

+5 −0
Original line number Diff line number Diff line
@@ -1337,6 +1337,7 @@ extern void perf_event_disable_inatomic(struct perf_event *event); 
extern void perf_event_task_tick(void);

extern int perf_event_account_interrupt(struct perf_event *event);

extern int perf_event_period(struct perf_event *event, u64 value);

extern u64 perf_event_pause(struct perf_event *event, bool reset);

#else /* !CONFIG_PERF_EVENTS: */

static inline void *

perf_aux_output_begin(struct perf_output_handle *handle,
@@ -1420,6 +1421,10 @@ static inline int perf_event_period(struct perf_event *event, u64 value) 
{

	return -EINVAL;

}

static inline u64 perf_event_pause(struct perf_event *event, bool reset)

{

	return 0;

}

#endif



#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)

kernel/events/core.c

+18 −0
Original line number Diff line number Diff line
@@ -5029,6 +5029,24 @@ static void _perf_event_reset(struct perf_event *event) 
	perf_event_update_userpage(event);

}



/* Assume it's not an event with inherit set. */

u64 perf_event_pause(struct perf_event *event, bool reset)

{

	struct perf_event_context *ctx;

	u64 count;



	ctx = perf_event_ctx_lock(event);

	WARN_ON_ONCE(event->attr.inherit);

	_perf_event_disable(event);

	count = local64_read(&event->count);

	if (reset)

		local64_set(&event->count, 0);

	perf_event_ctx_unlock(event, ctx);



	return count;

}

EXPORT_SYMBOL_GPL(perf_event_pause);



/*

 * Holding the top-level event's child_mutex means that any

 * descendant process that has inherited this event will block

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