lkml.org 
[lkml]   [2015]   [Aug]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] cred: Remove unnecessary kdebug atomic reads
From
Date
On Tue, 2015-08-25 at 13:39 -0700, Andrew Morton wrote:
> On Tue, 25 Aug 2015 09:53:51 -0700 Joe Perches <joe@perches.com> wrote:
> > commit e0e817392b9a ("CRED: Add some configurable debugging [try #6]")
> > added the kdebug mechanism to this file back in 2009.
> >
> > The kdebug macro calls no_printk which always evaluates arguments.
> >
> > Most of the kdebug uses have an unnecessary call of
> > atomic_read(&cred->usage)
> >
> > Make the kdebug macro do nothing by defining it with
> > do { if (0) no_printk(...); } while (0)
> > when not enabled.
[]
> Did you consider doing this within no_printk()?

Yes.

> That would break code
> which is relying on side-effects in the evaluation of a printk arg but
> that's pretty weird and I bet there isn't (and won't be) such code.

I'll bet you there is more than a little and I don't want to
experiment with it unconditionally.

All printks would need to be evaluated for that side-effect.

Safer would be to create a new no_eval_printk macro and convert
the no_printk uses over to that as appropriate and possibly create
a CONFIG_ option to use no_eval_printk instead of no_printk/printk
and let the adventurous find the side-effects.

Maybe a coccinelle script can be written to find all the locations
with evaluated non-constant expression arguments with side-effects.



\
 
 \ /
  Last update: 2015-08-25 23:21    [W:0.075 / U:0.992 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site