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authorPeter Zijlstra <peterz@infradead.org>2019-10-01 10:50:33 +0200
committerIngo Molnar <mingo@kernel.org>2019-10-01 21:27:50 +0200
commit73956fc07dd7b25d4a33ab3fdd6247c60d0b237c (patch)
treecbfbc86f18448d0e9cfd044bb2f0d6bf4389b423 /kernel
parentLinux 5.4-rc1 (diff)
downloadlinux-73956fc07dd7b25d4a33ab3fdd6247c60d0b237c.tar.xz
linux-73956fc07dd7b25d4a33ab3fdd6247c60d0b237c.zip
membarrier: Fix RCU locking bug caused by faulty merge
The following commit: 227a4aadc75b ("sched/membarrier: Fix p->mm->membarrier_state racy load") got fat fingered by me when merging it with other patches. It meant to move the RCU section out of the for loop but ended up doing it partially, leaving a superfluous rcu_read_lock() inside, causing havok. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> 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: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> 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> Cc: linux-tip-commits@vger.kernel.org Fixes: 227a4aadc75b ("sched/membarrier: Fix p->mm->membarrier_state racy load") Link: https://lkml.kernel.org/r/20191001085033.GP4519@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/membarrier.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index a39bed2c784f..168479a7d61b 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -174,7 +174,6 @@ static int membarrier_private_expedited(int flags)
*/
if (cpu == raw_smp_processor_id())
continue;
- rcu_read_lock();
p = rcu_dereference(cpu_rq(cpu)->curr);
if (p && p->mm == mm)
__cpumask_set_cpu(cpu, tmpmask);