Commit cf4957f1 authored Oct 24, 2012 by Jiri Olsa Committed by Arnaldo Carvalho de Melo Aug 07, 2013

perf: Add PERF_EVENT_IOC_ID ioctl to return event ID



The only way to get the event ID is by reading the event fd,
followed by parsing the ID value out of the returned data.

While this is ok for current read format used by perf tool,
it is not ok when we use PERF_FORMAT_GROUP format.

With this format the data are returned for the whole group
and there's no way to find out what ID belongs to our fd
(if we are not group leader event).

Adding a simple ioctl that returns event primary ID for given fd.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-v1bn5cto707jn0bon34afqr1@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 93786a5f

include/uapi/linux/perf_event.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -321,6 +321,7 @@ struct perf_event_attr {
		#define PERF_EVENT_IOC_PERIOD _IOW('$', 4, __u64)
		#define PERF_EVENT_IOC_SET_OUTPUT _IO ('$', 5)
		#define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
		#define PERF_EVENT_IOC_ID _IOR('$', 7, u64 *)

		enum perf_event_ioc_flags {
		PERF_IOC_FLAG_GROUP = 1U << 0,

kernel/events/core.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -3568,6 +3568,15 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
		case PERF_EVENT_IOC_PERIOD:
		return perf_event_period(event, (u64 __user *)arg);

		case PERF_EVENT_IOC_ID:
		{
		u64 id = primary_event_id(event);

		if (copy_to_user((void __user *)arg, &id, sizeof(id)))
		return -EFAULT;
		return 0;
		}

		case PERF_EVENT_IOC_SET_OUTPUT:
		{
		int ret;

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