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Subject[PATCH v3 14/14] 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>
---
kernel/events/uprobes.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 2d5b7bd..4e5e979 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);

--
1.5.5.1


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