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Message-Id: <20190919173705.2181-2-mathieu.desnoyers@efficios.com>
Date: Thu, 19 Sep 2019 13:36:59 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Peter Zijlstra <peterz@...radead.org>,
"Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
Oleg Nesterov <oleg@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Russell King - ARM Linux admin <linux@...linux.org.uk>,
Chris Metcalf <cmetcalf@...hip.com>,
Christoph Lameter <cl@...ux.com>,
Kirill Tkhai <tkhai@...dex.ru>, Mike Galbraith <efault@....de>,
Thomas Gleixner <tglx@...utronix.de>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH for 5.4 1/7] Fix: sched/membarrier: Private expedited registration check
Fix a logic flaw in the way membarrier_register_private_expedited()
handles ready state checks for private expedited sync core and private
expedited registrations.
If a private expedited membarrier registration is first performed, and
then a private expedited sync_core registration is performed, the ready
state check will skip the second registration when it really should not.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc: Chris Metcalf <cmetcalf@...hip.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Kirill Tkhai <tkhai@...dex.ru>
Cc: Mike Galbraith <efault@....de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
---
kernel/sched/membarrier.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index aa8d75804108..5110d91b1b0e 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -226,7 +226,7 @@ static int membarrier_register_private_expedited(int flags)
* groups, which use the same mm. (CLONE_VM but not
* CLONE_THREAD).
*/
- if (atomic_read(&mm->membarrier_state) & state)
+ if ((atomic_read(&mm->membarrier_state) & state) == state)
return 0;
atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED, &mm->membarrier_state);
if (flags & MEMBARRIER_FLAG_SYNC_CORE)
--
2.17.1
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