linux-kernel - Re: likely unlikely annotation (spinlock status)

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Date:	Fri, 07 Jan 2011 10:38:29 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	manikanta <manikanta4u@...il.com>
Cc:	mpm@...enic.com, linux-kernel@...r.kernel.org,
	cl@...ux-foundation.org
Subject: Re: likely unlikely annotation (spinlock status)

On Fri, 2011-01-07 at 15:57 +0530, manikanta wrote:
> Hi Rostedt,
>  
> Problem:    
> Likely and unlikely annotation branch summary is showing
> status for spinlocks(below is the result of enabling
> CONFIG_PROFILE_ANNOTATED_BRANCHES).
> Is it right(eventhough at line no 6753 i can see spin_unlock(lock))???

Your spin_unlock is probably a macro which contains an "if (likely())"
in it. If this is the case then it would definitely show a location of
the spin lock, because that spinlock is nothing more than an if
statement to gcc.

>  
> 0       19 100 __cond_resched_lock            sched.c
> 6753
> 0        0   X   dsp_event                             audio_xwb.c
> 355
>  
> I am seeing the same results for my drivers also i.e. where we have
> used spinlocks.
> It is showing the spinlocks results.At line number 355 there is a
> spinlock call in file
> audio_xwb.c.
>  
> Is it right to show spinlock status instead of likely and unlikely
> notations???

Yes, if the spinlocks are macros with likely/unlikely annotations.

>  
> Setup:Android + mach-msm

Unfortunately, I don't have this setup to look at it.

-- Steve



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