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authorOleg Nesterov <oleg@redhat.com>2015-07-21 15:40:36 +0200
committerIngo Molnar <mingo@kernel.org>2015-07-31 10:38:07 +0200
commit2a742cedcf13572999436676cbe36c3a9b733b0f (patch)
treebb614fd0d0204a48f9ff739bced7cb45567f9fdb /kernel/events
parent704bde3cc26a4cb34386c164107b59e09745a022 (diff)
uprobes: Fix the waitqueue_active() check in xol_free_insn_slot()
The xol_free_insn_slot()->waitqueue_active() check is buggy. We need mb() after we set the conditon for wait_event(), or xol_take_insn_slot() can miss the wakeup. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Pratyush Anand <panand@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134036.GA4799@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/uprobes.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 2d5b7bd337a7..4e5e9798aa0c 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1337,6 +1337,7 @@ static void xol_free_insn_slot(struct task_struct *tsk)
clear_bit(slot_nr, area->bitmap);
atomic_dec(&area->slot_count);
+ smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
if (waitqueue_active(&area->wq))
wake_up(&area->wq);