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 <[email protected]> --- 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 6a9c5e0..9a4f9df 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1336,6 +1336,7 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
