On Mon, Jun 03, 2019 at 06:46:54AM -0700, tip-bot for Peter Zijlstra wrote: > Commit-ID: fff9b6c7d26943a8eb32b58364b7ec6b9369746a > Gitweb: > https://git.kernel.org/tip/fff9b6c7d26943a8eb32b58364b7ec6b9369746a > Author: Peter Zijlstra <pet...@infradead.org> > AuthorDate: Fri, 24 May 2019 13:52:31 +0200 > Committer: Ingo Molnar <mi...@kernel.org> > 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) <pet...@infradead.org> > Reviewed-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> > Acked-by: Will Deacon <will.dea...@arm.com> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Thomas Gleixner <t...@linutronix.de> > Link: > https://lkml.kernel.org/r/20190524115231.gn2...@hirez.programming.kicks-ass.net > Signed-off-by: Ingo Molnar <mi...@kernel.org>
I'd appreciate if you could Cc: me in future changes to this doc. (as currently suggested by get_maintainer.pl). This is particularly annoying when you spend time to review such changes: https://lkml.kernel.org/r/20190528111558.GA9106@andrea Thanks, Andrea > --- > 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
