Re: [PATCH [RT] 11/14] optimize the !printk fastpath through thelock acquisition

[Gregory Haskins]

Pavel Machek wrote:
> Hi!
>
> > Decorate the printk path with an "unlikely()"
> >
> > Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
> > ---
> >
> >  kernel/rtmutex.c |    8 ++++----
> >  1 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
> > index 122f143..ebdaa17 100644
> > --- a/kernel/rtmutex.c
> > +++ b/kernel/rtmutex.c
> > @@ -660,12 +660,12 @@ rt_spin_lock_fastlock(struct rt_mutex *lock,
> >  		void fastcall (*slowfn)(struct rt_mutex *lock))
> >  {
> >  	/* Temporary HACK! */
> > -	if (!current->in_printk)
> > -		might_sleep();
> > -	else if (in_atomic() || irqs_disabled())
> > +	if (unlikely(current->in_printk) && (in_atomic() || irqs_disabled()))
> >  		/* don't grab locks for printk in atomic */
> >  		return;
> >  
> > +	might_sleep();
>
> I think you changed the code here... you call might_sleep() in
> different cases afaict.

Agreed, but it's still correct afaict.  I added an extra might_sleep() 
to a path that really might sleep.  I should have mentioned that in the 
header.

In any case, its moot.  Andi indicated this patch is probably a no-op so 
I was considering dropping it on the v2 pass.

Regards,
-Greg



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