lkml.org 
[lkml]   [2019]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Input: alps: Drop unlikely before IS_ERR(_OR_NULL)
Hi Joe,

On Wed, Jun 05, 2019 at 07:28:53PM -0700, Joe Perches wrote:
> On Thu, 2019-06-06 at 09:08 +0800, Kefeng Wang wrote:
> > On 2019/6/5 22:42, Pali Rohár wrote:
> > > On Wednesday 05 June 2019 22:24:28 Kefeng Wang wrote:
> > > > IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag,
> > > > so no need to do that again from its callers. Drop it.
> > > Hi! I already reviewed this patch and rejected it, see:
> > > https://patchwork.kernel.org/patch/10817475/
> > OK, please ignore it.
>
> I think the stated reason of better readability isn't
> particularly sensible as the object code produced is
> actually slightly larger.
>
> x86-64 defconfig (gcc 8.3.0)
>
> $ size drivers/input/mouse/alps.o*
> text data bss dec hex filename
> 29416 56 0 29472 7320 drivers/input/mouse/alps.o.new
> 29432 56 0 29488 7330 drivers/input/mouse/alps.o.old

If gcc produces worse code for double unlikely, you should probably
report it to gcc folks, no? Or double unlikely turns into likely?

>
> Also if this unlikely is _really_ useful, perhaps the
> !IS_ERR immediately after could also use likely as the
> test seems only done for an OOM condition.

No, once you take the IS_ERR_OR_NULL(priv->dev3) == true branch it stops
being hot path and additional annotations are completely unneeded.

And if we failed to create and register priv->dev3 device - that's an
error and system is degraded. Can't do much here.

Thanks.

--
Dmitry

\
 
 \ /
  Last update: 2019-06-12 02:59    [W:0.109 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site