Re: [PATCH] mutex: Do not spin/queue before performing ww_mutex deadlock avoidance

From: Chris Wilson
Date: Thu May 26 2016 - 06:43:38 EST

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)

Chris Wilson, Intel Open Source Technology Centre