From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: "Chris Wilson" <chris@chris-wilson.co.uk>,
"Peter Zijlstra" <peterz@infradead.org>,
"Ingo Molnar" <mingo@redhat.com>,
intel-gfx@lists.freedesktop.org,
"Christian König" <christian.koenig@amd.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mutex: Do not spin/queue before performing ww_mutex deadlock avoidance
Date: Thu, 26 May 2016 13:08:58 +0200 [thread overview]
Message-ID: <5c99773f-448d-6ca7-e28e-c262a82ee58a@linux.intel.com> (raw)
In-Reply-To: <20160526104329.GS15901@nuc-i3427.alporthouse.com>
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
next prev parent reply other threads:[~2016-05-26 11:08 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-26 8:31 [PATCH] mutex: Do not spin/queue before performing ww_mutex deadlock avoidance Chris Wilson
2016-05-26 8:31 ` Chris Wilson
2016-05-26 9:02 ` ✗ Ro.CI.BAT: warning for " Patchwork
2016-05-26 10:37 ` [PATCH] " Maarten Lankhorst
2016-05-26 10:43 ` Chris Wilson
2016-05-26 10:43 ` Chris Wilson
2016-05-26 11:08 ` Maarten Lankhorst [this message]
2016-05-26 20:08 ` [PATCH] mutex: Report recursive ww_mutex locking early Chris Wilson
2016-05-26 20:08 ` Chris Wilson
2016-05-30 7:43 ` Maarten Lankhorst
2016-05-30 9:11 ` Peter Zijlstra
2016-05-30 9:11 ` Peter Zijlstra
2016-05-30 9:43 ` Maarten Lankhorst
2016-05-30 9:43 ` Maarten Lankhorst
2016-05-30 10:27 ` Peter Zijlstra
2016-05-30 10:45 ` Chris Wilson
2016-05-30 11:16 ` Maarten Lankhorst
2016-05-30 11:16 ` Maarten Lankhorst
2016-06-03 10:46 ` [tip:locking/core] locking/ww_mutex: " tip-bot for Chris Wilson
2016-05-27 5:34 ` ✗ Ro.CI.BAT: warning for mutex: Do not spin/queue before performing ww_mutex deadlock avoidance (rev2) Patchwork
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5c99773f-448d-6ca7-e28e-c262a82ee58a@linux.intel.com \
--to=maarten.lankhorst@linux.intel.com \
--cc=chris@chris-wilson.co.uk \
--cc=christian.koenig@amd.com \
--cc=intel-gfx@lists.freedesktop.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.