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]>
This commit is contained in:
Peter Zijlstra 2019-05-24 13:52:31 +02:00 • committed by Ingo Molnar
commit fff9b6c7d2

View file

@ -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