From: Thomas Gleixner <tglx@linutronix.de>
To: Davidlohr Bueso <dave@stgolabs.net>,
Alex Shi <alex.shi@linux.alibaba.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] locking/rtmutex: remove unused cmpxchg_relaxed
Date: Fri, 31 Jan 2020 21:23:01 +0100 [thread overview]
Message-ID: <87r1zfxtne.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200131173922.hjvugxuybrn2wbsn@linux-p48b>
Davidlohr Bueso <dave@stgolabs.net> writes:
> On Tue, 21 Jan 2020, Alex Shi wrote:
Subject: locking/rtmutex: remove unused cmpxchg_relaxed
should be
Subject: locking/rtmutex: Remove unused rt_mutex_cmpxchg_relaxed()
You're not removing cmpxchg_relaxed, right?
>> No one use this macro after it was introduced. Better to remove it?
Please make that factual.
The macro was never used at all. Remove it.
> You also need to remove it for the CONFIG_DEBUG_RT_MUTEXES=y case.
Yes.
> Hmm unrelated, but do we want CCAS for rtmutex fastpath? Ie:
>
> (l->owner == c && cmpxchg_acquire(&l->owner, c, n) == c)
>
> That would optimize for the contended case and avoid the cmpxchg - it would
> also help if we ever do the top-waiter spin thing.
Not sure if it buys much, but it kinda makes sense.
Thanks,
tglx
next prev parent reply other threads:[~2020-01-31 20:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 8:34 [PATCH] locking/rtmutex: remove unused cmpxchg_relaxed Alex Shi
2020-01-31 17:39 ` Davidlohr Bueso
2020-01-31 20:23 ` Thomas Gleixner [this message]
2020-02-04 10:18 ` Alex Shi
2020-02-12 15:07 ` Davidlohr Bueso
2020-02-14 15:17 ` [PATCH 1/2] locking/rtmutex: Remove unused rt_mutex_cmpxchg_relaxed() Alex Shi
2020-02-14 15:17 ` [PATCH 2/2] locking/rtmutex: optimize rt_mutex_cmpxchgs Alex Shi
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