40 lines
1.4 KiB
Diff
40 lines
1.4 KiB
Diff
From: Peter Zijlstra <peterz@infradead.org>
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Date: Wed, 22 Mar 2017 11:35:49 +0100
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Subject: [PATCH] futex: Use smp_store_release() in mark_wake_futex()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patches-4.11.9-rt7.tar.xz
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Upstream commit 1b367ece0d7e696cab1c8501bab282cc6a538b3f
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Since the futex_q can dissapear the instruction after assigning NULL,
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this really should be a RELEASE barrier. That stops loads from hitting
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dead memory too.
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Cc: juri.lelli@arm.com
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Cc: bigeasy@linutronix.de
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Cc: xlpang@redhat.com
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Cc: rostedt@goodmis.org
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Cc: mathieu.desnoyers@efficios.com
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Cc: jdesfossez@efficios.com
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Cc: dvhart@infradead.org
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Cc: bristot@redhat.com
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Link: http://lkml.kernel.org/r/20170322104151.604296452@infradead.org
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/futex.c | 3 +--
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1 file changed, 1 insertion(+), 2 deletions(-)
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--- a/kernel/futex.c
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+++ b/kernel/futex.c
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@@ -1290,8 +1290,7 @@ static void mark_wake_futex(struct wake_
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* memory barrier is required here to prevent the following
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* store to lock_ptr from getting ahead of the plist_del.
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*/
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- smp_wmb();
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- q->lock_ptr = NULL;
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+ smp_store_release(&q->lock_ptr, NULL);
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}
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static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *top_waiter,
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