>From 8d2b219794221e3ef1a1ec90e0f4fe344af9a55d Mon Sep 17 00:00:00 2001 From: Manfred Spraul Date: Fri, 11 Oct 2019 10:33:26 +0200 Subject: [PATCH 1/5] smp_mb__{before,after}_atomic(): Update Documentation When adding the _{acquire|release|relaxed}() variants of some atomic operations, it was forgotten to update Documentation/memory_barrier.txt: smp_mb__before_atomic and smp_mb__after_atomic can be combined with all RMW operations that do not imply memory barriers. In order to avoid that this happens again: Remove the paragraph from Documentation/memory_barrier.txt, the functions are sufficiently documented in Documentation/atomic_{t,bitops}.txt Fixes: 654672d4ba1a ("locking/atomics: Add _{acquire|release|relaxed}() variants of some atomic operations") Signed-off-by: Manfred Spraul Acked-by: Waiman Long Cc: Davidlohr Bueso Cc: Peter Zijlstra Cc: Will Deacon --- Documentation/memory-barriers.txt | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 1adbb8a371c7..16dfb4cde1e1 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -1873,25 +1873,7 @@ There are some more advanced barrier functions: (*) smp_mb__before_atomic(); (*) smp_mb__after_atomic(); - These are for use with atomic (such as add, subtract, increment and - decrement) functions that don't return a value, especially when used for - reference counting. These functions do not imply memory barriers. - - These are also used for atomic bitop functions that do not return a - value (such as set_bit and clear_bit). - - As an example, consider a piece of code that marks an object as being dead - and then decrements the object's reference count: - - obj->dead = 1; - smp_mb__before_atomic(); - atomic_dec(&obj->ref_count); - - This makes sure that the death mark on the object is perceived to be set - *before* the reference counter is decremented. - - See Documentation/atomic_{t,bitops}.txt for more information. - + See Documentation/atomic_{t,bitops}.txt for information. (*) dma_wmb(); (*) dma_rmb(); -- 2.23.0