Messages in this thread | | | Subject | Re: [PATCH] mutex: Do not spin/queue before performing ww_mutex deadlock avoidance | From | Maarten Lankhorst <> | Date | Thu, 26 May 2016 13:08:58 +0200 |
| |
Op 26-05-16 om 12:43 schreef Chris Wilson: > On Thu, May 26, 2016 at 12:37:30PM +0200, Maarten Lankhorst wrote: >> The check should also not be for NULL, but for use_ww_ctx. >> This way the if check is optimized out for the ww_ctx path, where >> ww_ctx is always non-null. > The compiler can see use_ww_ctx == false => ww_ctx == NULL just as well > to do dead-code elimination, i.e. use_ww_ctx is superflouus and does not > reduce the code size. (gcc 4.7.2, 4.9.1, 5.3.1) That's true, but it cannot do the same when use_ww_ctx = true. In this case the function will always be called with ww_ctx != NULL, but the compiler can't see that, so it will keep the check even if it's always true.
~Maarten
| |