linux-kernel - [PATCH AUTOSEL 3.18 84/98] perf: Fix PERF_EVENT_IOC

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Message-Id: <20181025141853.214051-84-sashal@kernel.org>
Date:   Thu, 25 Oct 2018 10:18:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Alexander Potapenko <glider@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sasha.levin@...cle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 3.18 84/98] perf: Fix PERF_EVENT_IOC_PERIOD deadlock

From: Peter Zijlstra <peterz@...radead.org>

[ Upstream commit 642c2d671ceff40e9453203ea0c66e991e11e249 ]

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>
Signed-off-by: Sasha Levin <sashal@...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 1f08f691de59..7b2f9d432fe7 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3929,7 +3929,14 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg)
 		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;
-- 
2.17.1