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Message-ID: <20160520150049.GB7086@linux-uzut.site>
Date:	Fri, 20 May 2016 08:00:49 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	manfred@...orfullife.com, Waiman.Long@....com, mingo@...nel.org,
	torvalds@...ux-foundation.org, ggherdovich@...e.com,
	mgorman@...hsingularity.net, linux-kernel@...r.kernel.org
Subject: Re: sem_lock() vs qspinlocks

On Fri, 20 May 2016, Peter Zijlstra wrote:

>On Thu, May 19, 2016 at 10:39:26PM -0700, Davidlohr Bueso wrote:
>>  In addition, this makes me wonder if queued_spin_is_locked() should then be:
>>
>> -	return atomic_read(&lock->val);
>> +	return atomic_read(&lock->val) & _Q_LOCKED_MASK;
>>
>> And avoid considering pending waiters as locked.
>
>Probably

Similarly, and I know you hate it, but afaict, then semantically
queued_spin_is_contended() ought to be:

-       return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
+       return atomic_read(&lock->val);

Thanks,
Davidlohr

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