From: Chris Metcalf Date: Mon, 23 Nov 2015 22:04:17 +0000 (-0500) Subject: Documentation/memory-barriers.txt: Fix ACCESS_ONCE thinko X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=f84cfbb0ff269b427a0db591e22ac6948c554ab4;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git Documentation/memory-barriers.txt: Fix ACCESS_ONCE thinko In commit 2ecf810121c7 ("Documentation/memory-barriers.txt: Add needed ACCESS_ONCE() calls to memory-barriers.txt") the statement "Q = P" was converted to "ACCESS_ONCE(Q) = P". This should have been "Q = ACCESS_ONCE(P)". It later became "WRITE_ONCE(Q, P)". This doesn't match the following text, which is "Q = LOAD P". Change the statement to be "Q = READ_ONCE(P)". Signed-off-by: Chris Metcalf Signed-off-by: Paul E. McKenney --- diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index aef9487303d0..85304ebd187c 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -194,7 +194,7 @@ There are some minimal guarantees that may be expected of a CPU: (*) On any given CPU, dependent memory accesses will be issued in order, with respect to itself. This means that for: - WRITE_ONCE(Q, P); smp_read_barrier_depends(); D = READ_ONCE(*Q); + Q = READ_ONCE(P); smp_read_barrier_depends(); D = READ_ONCE(*Q); the CPU will issue the following memory operations: @@ -202,9 +202,9 @@ There are some minimal guarantees that may be expected of a CPU: and always in that order. On most systems, smp_read_barrier_depends() does nothing, but it is required for DEC Alpha. The READ_ONCE() - and WRITE_ONCE() are required to prevent compiler mischief. Please - note that you should normally use something like rcu_dereference() - instead of open-coding smp_read_barrier_depends(). + is required to prevent compiler mischief. Please note that you + should normally use something like rcu_dereference() instead of + open-coding smp_read_barrier_depends(). (*) Overlapping loads and stores within a particular CPU will appear to be ordered within that CPU. This means that for: