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17 May 2024, 09:02:56 UTC
Revision 6e7ca09b583de4be6c27d9d4b06e8c5dd46a58fa authored by Nikolay Borisov on 25 July 2019, 08:27:29 UTC, committed by David Sterba on 25 July 2019, 15:34:08 UTC 
btrfs: Fix deadlock caused by missing memory barrier
 
Commit 06297d8cefca ("btrfs: switch extent_buffer blocking_writers from
atomic to int") changed the type of blocking_writers but forgot to
adjust relevant code in btrfs_tree_unlock by converting the
smp_mb__after_atomic to smp_mb.  This opened up the possibility of a
deadlock due to re-ordering of setting blocking_writers and
checking/waking up the waiter. This particular lockup is explained in a
comment above waitqueue_active() function.

Fix it by converting the memory barrier to a full smp_mb, accounting
for the fact that blocking_writers is a simple integer.

Fixes: 06297d8cefca ("btrfs: switch extent_buffer blocking_writers from atomic to int")
Tested-by: Johannes Thumshirn <jthumshirn@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
1 parent 373c3b8
History
Tip revision: 6e7ca09b583de4be6c27d9d4b06e8c5dd46a58fa authored by Nikolay Borisov on 25 July 2019, 08:27:29 UTC
btrfs: Fix deadlock caused by missing memory barrier
Tip revision: 6e7ca09
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