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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: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Like Xu <like.xu@linux.intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Like Xu 2019-10-27 18:52:39 +08:00 committed by Paolo Bonzini
parent 3ca270fc9e
commit 52ba4b0b99
2 changed files with 23 additions and 0 deletions
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5
include/linux/perf_event.h
View File

@ -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)

18
kernel/events/core.c
View File

@ -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