From 8238b4579866b7c1bb99883cfe102a43db5506ff Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 26 Aug 2022 09:17:08 -0400 Subject: 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 Acked-by: Will Deacon Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds --- include/linux/bitops.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index cf9bf65039f2..3b89c64bcfd8 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -59,6 +59,7 @@ extern unsigned long __sw_hweight64(__u64 w); #define __test_and_clear_bit(nr, addr) bitop(___test_and_clear_bit, nr, addr) #define __test_and_change_bit(nr, addr) bitop(___test_and_change_bit, nr, addr) #define test_bit(nr, addr) bitop(_test_bit, nr, addr) +#define test_bit_acquire(nr, addr) bitop(_test_bit_acquire, nr, addr) /* * Include this here because some architectures need generic_ffs/fls in -- cgit v1.2.3-73-gaa49b