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authorMikulas Patocka <mpatocka@redhat.com>2022-08-26 16:17:08 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-08-26 19:30:25 +0300
commit8238b4579866b7c1bb99883cfe102a43db5506ff (patch)
treea61b3a10f1d6b53bc7c05b08b8b49bb84156ee2e /kernel/sched
parent4c612826bec1441214816827979b62f84a097e91 (diff)
downloadlinux-8238b4579866b7c1bb99883cfe102a43db5506ff.tar.xz
wait_on_bit: add an acquire memory barrier
There are several places in the kernel where wait_on_bit is not followed by a memory barrier (for example, in drivers/md/dm-bufio.c:new_read). On architectures with weak memory ordering, it may happen that memory accesses that follow wait_on_bit are reordered before wait_on_bit and they may return invalid data. Fix this class of bugs by introducing a new function "test_bit_acquire" that works like test_bit, but has acquire memory ordering semantics. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Acked-by: Will Deacon <will@kernel.org> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/wait_bit.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/wait_bit.c b/kernel/sched/wait_bit.c
index d4788f810b55..0b1cd985dc27 100644
--- a/kernel/sched/wait_bit.c
+++ b/kernel/sched/wait_bit.c
@@ -47,7 +47,7 @@ __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_
prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);
if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags))
ret = (*action)(&wbq_entry->key, mode);
- } while (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret);
+ } while (test_bit_acquire(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret);
finish_wait(wq_head, &wbq_entry->wq_entry);