Messages in this thread | | | Subject | Re: [PATCH] cred: Remove unnecessary kdebug atomic reads | From | Joe Perches <> | Date | Tue, 25 Aug 2015 13:51:06 -0700 |
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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.
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