Commit-ID: 60beda849343494b2a598b927630bbe293c1cc6e
Gitweb: http://git.kernel.org/tip/60beda849343494b2a598b927630bbe293c1cc6e
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 26 Jan 2016 14:55:02 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 29 Jan 2016 08:35:34 +0100
perf: Untangle 'owner' confusion
There are two concepts of owner wrt an event and they are conflated:
- event::owner / event::owner_list,
used by prctl(.option = PR_TASK_PERF_EVENTS_{EN,DIS}ABLE).
- the 'owner' of the event object, typically the file descriptor.
Currently these two concepts are conflated, which gives trouble with
scm_rights passing of file descriptors. Passing the event and then
closing the creating task would render the event 'orphan' and would
have it cleared out. Unlikely what is expectd.
This patch untangles these two concepts by using PERF_EVENT_STATE_EXIT
to denote the second type.
Reported-by: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/core.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4291a4d..e549cf2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1650,7 +1650,7 @@ out:
*/
static bool is_orphaned_event(struct perf_event *event)
{
- return event && !is_kernel_event(event) && !READ_ONCE(event->owner);
+ return event && event->state == PERF_EVENT_STATE_EXIT;
}
/*
@@ -1771,6 +1771,7 @@ group_sched_out(struct perf_event *group_event,
}
#define DETACH_GROUP 0x01UL
+#define DETACH_STATE 0x02UL
/*
* Cross CPU call to remove a performance event
@@ -1790,6 +1791,8 @@ __perf_remove_from_context(struct perf_event *event,
if (flags & DETACH_GROUP)
perf_group_detach(event);
list_del_event(event, ctx);
+ if (flags & DETACH_STATE)
+ event->state = PERF_EVENT_STATE_EXIT;
if (!ctx->nr_events && ctx->is_active) {
ctx->is_active = 0;
@@ -3801,9 +3804,16 @@ static void put_event(struct perf_event *event)
*/
ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING);
WARN_ON_ONCE(ctx->parent_ctx);
- perf_remove_from_context(event, DETACH_GROUP);
+ perf_remove_from_context(event, DETACH_GROUP | DETACH_STATE);
perf_event_ctx_unlock(event, ctx);
+ /*
+ * At this point we must have event->state == PERF_EVENT_STATE_EXIT,
+ * either from the above perf_remove_from_context() or through
+ * perf_event_exit_event().
+ */
+ WARN_ON_ONCE(event->state != PERF_EVENT_STATE_EXIT);
+
_free_event(event);
}
--
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