sched/membarrier: Fix private expedited registration check

BugLink: https://bugs.launchpad.net/bugs/1848039
[ Upstream commit fc0d77387cb5ae883fd774fc559e056a8dde024c ]

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@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190919173705.2181-2-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index aa8d7580410887d319623353c88b37dfe54d7645..5110d91b1b0eab771febf668c678893055b0c77e 100644 (file)
--- 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)