linux-kernel - [PATCH] afs: Add missing memory barriers in afs_manage

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Date:   Mon, 26 Nov 2018 17:44:12 +0100
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Andrea Parri <andrea.parri@...rulasolutions.com>
Subject: [PATCH] afs: Add missing memory barriers in afs_manage_cell()

As the comments for wake_up_bit() and waitqueue_active() point out,
the barriers are needed to order the clearing of the _FL_NOT_READY
bit and the waitqueue_active() load; match the implicit barrier in
prepare_to_wait().

Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
---
 fs/afs/cell.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index cf445dbd5f2e0..a9488abe56029 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -637,6 +637,7 @@ static void afs_manage_cell(struct work_struct *work)
 		cell->state = AFS_CELL_ACTIVE;
 		smp_wmb();
 		clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
+		smp_mb__after_atomic(); /* see comment for wake_up_bit() */
 		wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
 		goto again;
 
@@ -678,6 +679,7 @@ static void afs_manage_cell(struct work_struct *work)
 	cell->state = AFS_CELL_ACTIVE;
 	smp_wmb();
 	clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
+	smp_mb__after_atomic(); /* see comment for wake_up_bit() */
 	wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
 	_leave(" [deact->act]");
 	return;
-- 
2.17.1