linux-kernel - [tip:perf/core] perf: Fix PERF_EVENT_IOC

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Date:	Fri, 4 Dec 2015 03:50:10 -0800
From:	tip-bot for Peter Zijlstra <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	dvyukov@...gle.com, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org, sasha.levin@...cle.com,
	hpa@...or.com, acme@...nel.org, acme@...hat.com, glider@...gle.com,
	edumazet@...gle.com, tglx@...utronix.de, vincent.weaver@...ne.edu,
	jolsa@...hat.com, mingo@...nel.org, torvalds@...ux-foundation.org,
	kcc@...gle.com, peterz@...radead.org, eranian@...gle.com
Subject: [tip:perf/core] perf: Fix PERF_EVENT_IOC_PERIOD deadlock

Commit-ID:  642c2d671ceff40e9453203ea0c66e991e11e249
Gitweb:     http://git.kernel.org/tip/642c2d671ceff40e9453203ea0c66e991e11e249
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Mon, 30 Nov 2015 12:56:15 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 4 Dec 2015 10:08:03 +0100

perf: Fix PERF_EVENT_IOC_PERIOD deadlock

Dmitry reported a fairly silly recursive lock deadlock for
PERF_EVENT_IOC_PERIOD, fix this by explicitly doing the inactive part of
__perf_event_period() instead of calling that function.

Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: <stable@...r.kernel.org>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Kostya Serebryany <kcc@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sasha Levin <sasha.levin@...cle.com>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Fixes: c7999c6f3fed ("perf: Fix PERF_EVENT_IOC_PERIOD migration race")
Link: http://lkml.kernel.org/r/20151130115615.GJ17308@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/events/core.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5854fcf..49a5118 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4225,7 +4225,14 @@ retry:
 		goto retry;
 	}
 
-	__perf_event_period(&pe);
+	if (event->attr.freq) {
+		event->attr.sample_freq = value;
+	} else {
+		event->attr.sample_period = value;
+		event->hw.sample_period = value;
+	}
+
+	local64_set(&event->hw.period_left, 0);
 	raw_spin_unlock_irq(&ctx->lock);
 
 	return 0;
--
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