[PATCH 1/3] writeback: add memory barrier before wake_up_bit() in bdi_work_free()

[Jens Axboe]

As per wake_up_bit() documentation, was also triggered in the wild.
Process got stuck forever waiting for a bit clear that had happened.

Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
---
 fs/fs-writeback.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index a287c09..6052701 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -102,6 +102,7 @@ static void bdi_work_free(struct rcu_head *head)
 		kfree(work);
 	else {
 		clear_bit(0, &work->state);
+		smp_mb__after_clear_bit();
 		wake_up_bit(&work->state, 0);
 	}
 }
-- 
1.6.3.9.g6345


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