linux-kernel - Re: [tip: locking/urgent] locking/ww_mutex: Simplify use_ww_ctx & ww

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Message-ID: <YFIKWCUAZabBsji0@hirez.programming.kicks-ass.net>
Date:   Wed, 17 Mar 2021 14:55:36 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>,
        Davidlohr Bueso <dbueso@...e.de>, x86@...nel.org
Subject: Re: [tip: locking/urgent] locking/ww_mutex: Simplify use_ww_ctx &
 ww_ctx handling

On Wed, Mar 17, 2021 at 09:43:20AM -0400, Waiman Long wrote:

> Using gcc 8.4.1, the generated __mutex_lock function has the same size (with
> last instruction at offset +5179) with or without this patch. Well, you can
> say that this patch is an no-op wrt generated code.

OK, then GCC has gotten better. Because back then I tried really hard
but it wouldn't remove the if (ww_ctx) branches unless I had that extra
const bool argument.