This would be better titled as:
compiler: don't return a value from WRITE_ONCE() ... since we do want the WRITE_ONCE() itself to be evaluated. On Fri, May 24, 2019 at 12:35:36PM +0200, Andrea Parri wrote: > Now that there's no single use of the value of WRITE_ONCE(), change > the implementation to eliminate it. I hope that's the case, but it's possible that some macros might be relying on this, so it's probably worth waiting to see if the kbuild test robot screams. Otherwise, I agree that WRITE_ONCE() returning a value is surprising, and unnecessary. IIRC you said that trying to suport that in other implementations was painful, so aligning on a non-returning version sounds reasonable to me. > > Suggested-by: Mark Rutland <[email protected]> > Signed-off-by: Andrea Parri <[email protected]> > Cc: Arnd Bergmann <[email protected]> > Cc: Greg Kroah-Hartman <[email protected]> > Cc: Jorgen Hansen <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Will Deacon <[email protected]> > Cc: Mark Rutland <[email protected]> > Cc: "Paul E. McKenney" <[email protected]> > --- > include/linux/compiler.h | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 8aaf7cd026b06..4024c809a6c63 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -277,12 +277,11 @@ unsigned long read_word_at_a_time(const void *addr) > } > > #define WRITE_ONCE(x, val) \ > -({ \ > +do { \ > union { typeof(x) __val; char __c[1]; } __u = \ > { .__val = (__force typeof(x)) (val) }; \ > __write_once_size(&(x), __u.__c, sizeof(x)); \ > - __u.__val; \ > -}) > +} while (0) With the title fixed, and assuming that the kbuild test robot doesn't find uses we've missed: Acked-by: Mark Rutland <[email protected]> Thanks, Mark. > > #endif /* __KERNEL__ */ > > -- > 2.7.4 >
