From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, vince@deater.net,
eranian@google.com, Arnaldo Carvalho de Melo <acme@infradead.org>,
Jiri Olsa <jolsa@kernel.org>
Subject: Re: [PATCH] perf: Synchronously cleanup child events
Date: Mon, 18 Jan 2016 14:37:06 +0200 [thread overview]
Message-ID: <8760yr83nx.fsf@ashishki-desk.ger.corp.intel.com> (raw)
In-Reply-To: <20160115175759.GL3421@worktop>
Peter Zijlstra <peterz@infradead.org> writes:
> I suspect this races against inherit_event(), like:
>
> inherit_event() perf_event_release_kernel()
>
> if (is_orphaned_event(parent_event) /* false */
>
> event->owner = NULL
>
> mutex_lock(child_mutex);
> list_splice
> mutex_unlock(child_mutex);
>
> mutex_lock(child_mutex);
> list_add_tail
> mutex_unlock(child_mutex);
Or how about this instead:
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8eb3fee429..cd9f1ac537 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3786,8 +3786,9 @@ int perf_event_release_kernel(struct perf_event *event)
event->owner = NULL;
+retry:
/*
- * event::child_mutex nests inside ctx::lock, so move children
+ * event::child_mutex nests inside ctx::mutex, so move children
* to a safe place first and avoid inversion
*/
mutex_lock(&event->child_mutex);
@@ -3818,8 +3819,13 @@ int perf_event_release_kernel(struct perf_event *event)
put_event(event);
}
- /* Must be the last reference */
+ /* Must be the last reference, .. */
put_event(event);
+
+ /* .. unless we raced with inherit_event(), in which case, repeat */
+ if (atomic_long_inc_not_zero(&event->refcount))
+ goto retry;
+
return 0;
}
EXPORT_SYMBOL_GPL(perf_event_release_kernel);
next prev parent reply other threads:[~2016-01-18 12:37 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 11:22 [PATCH] perf: Cleanup user's child events Alexander Shishkin
2016-01-15 12:54 ` Peter Zijlstra
2016-01-15 13:05 ` Alexander Shishkin
2016-01-15 13:09 ` Peter Zijlstra
2016-01-15 14:07 ` [PATCH] perf: Synchronously cleanup " Alexander Shishkin
2016-01-15 17:57 ` Peter Zijlstra
2016-01-18 12:07 ` Alexander Shishkin
2016-01-18 12:37 ` Alexander Shishkin [this message]
2016-01-18 14:44 ` Peter Zijlstra
2016-01-19 15:12 ` [PATCH v2] " Alexander Shishkin
2016-01-19 20:05 ` Peter Zijlstra
2016-01-19 21:58 ` Alexei Starovoitov
2016-01-20 8:32 ` Peter Zijlstra
2016-01-21 4:55 ` Alexei Starovoitov
2016-01-20 7:04 ` Alexander Shishkin
2016-01-20 8:03 ` Peter Zijlstra
2016-01-22 11:35 ` Alexander Shishkin
2016-01-22 12:12 ` Peter Zijlstra
2016-01-22 12:38 ` Peter Zijlstra
2016-01-22 19:44 ` Alexei Starovoitov
2016-01-25 11:48 ` Peter Zijlstra
2016-01-25 14:54 ` Peter Zijlstra
2016-01-25 21:04 ` Peter Zijlstra
2016-01-26 4:59 ` Alexei Starovoitov
2016-01-26 16:16 ` Peter Zijlstra
2016-01-26 17:24 ` Peter Zijlstra
2016-01-26 23:31 ` Alexei Starovoitov
2016-01-27 9:58 ` Peter Zijlstra
2016-01-27 17:52 ` Alexei Starovoitov
2016-01-29 11:28 ` [tip:perf/urgent] perf/bpf: Convert perf_event_array to use struct file tip-bot for Alexei Starovoitov
2016-01-29 20:01 ` Alexei Starovoitov
2016-01-19 20:07 ` [PATCH v2] perf: Synchronously cleanup child events Peter Zijlstra
2016-01-19 7:45 ` [PATCH] " Ingo Molnar
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