Commit-ID: fff9b6c7d26943a8eb32b58364b7ec6b9369746a Gitweb: https://git.kernel.org/tip/fff9b6c7d26943a8eb32b58364b7ec6b9369746a Author: Peter Zijlstra <[email protected]> AuthorDate: Fri, 24 May 2019 13:52:31 +0200 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 3 Jun 2019 12:32:57 +0200
Documentation/atomic_t.txt: Clarify pure non-rmw usage Clarify that pure non-RMW usage of atomic_t is pointless, there is nothing 'magical' about atomic_set() / atomic_read(). This is something that seems to confuse people, because I happen upon it semi-regularly. Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Greg Kroah-Hartman <[email protected]> Acked-by: Will Deacon <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- Documentation/atomic_t.txt | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt index dca3fb0554db..89eae7f6b360 100644 --- a/Documentation/atomic_t.txt +++ b/Documentation/atomic_t.txt @@ -81,9 +81,11 @@ Non-RMW ops: The non-RMW ops are (typically) regular LOADs and STOREs and are canonically implemented using READ_ONCE(), WRITE_ONCE(), smp_load_acquire() and -smp_store_release() respectively. +smp_store_release() respectively. Therefore, if you find yourself only using +the Non-RMW operations of atomic_t, you do not in fact need atomic_t at all +and are doing it wrong. -The one detail to this is that atomic_set{}() should be observable to the RMW +A subtle detail of atomic_set{}() is that it should be observable to the RMW ops. That is: C atomic-set
