From: Davidlohr Bueso <dave@stgolabs.net>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Waiman Long <Waiman.Long@hpe.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [PATCH tip/locking/core v8 1/5] locking/qspinlock: Use _acquire/_release versions of cmpxchg & xchg
Date: Mon, 19 Oct 2015 20:46:02 -0700 [thread overview]
Message-ID: <20151020034602.GC27292@linux-uzut.site> (raw)
In-Reply-To: <20151020031714.GA935@fixme-laptop.cn.ibm.com>
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On Tue, 20 Oct 2015, Boqun Feng wrote:
>> @@ -93,7 +94,7 @@ static __always_inline void queued_spin_unlock(struct qspinlock *lock)
>> /*
>> * smp_mb__before_atomic() in order to guarantee release semantics
>> */
>> - smp_mb__before_atomic_dec();
>> + smp_mb__before_atomic();
>> atomic_sub(_Q_LOCKED_VAL, &lock->val);
>
>Just be curious, you don't use atomic_sub_release() here on purpose?
atomic_sub() does not imply barriers, so there's no relaxed variants; that's
only for _return() (and such) to the caller.
Thanks,
Davidlohr
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next prev parent reply other threads:[~2015-10-20 3:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-15 22:51 [PATCH tip/locking/core v8 0/5] locking/qspinlock: Enhance pvqspinlock performance Waiman Long
2015-10-15 22:51 ` [PATCH tip/locking/core v8 1/5] locking/qspinlock: Use _acquire/_release versions of cmpxchg & xchg Waiman Long
2015-10-20 3:17 ` Boqun Feng
2015-10-20 3:46 ` Davidlohr Bueso [this message]
2015-10-20 3:48 ` Boqun Feng
2015-10-15 22:51 ` [PATCH tip/locking/core v8 2/5] locking/pvqspinlock, x86: Optimize PV unlock code path Waiman Long
2015-10-15 22:51 ` [PATCH tip/locking/core v8 3/5] locking/pvqspinlock: Collect slowpath lock statistics Waiman Long
2015-10-15 22:51 ` [PATCH tip/locking/core v8 4/5] locking/pvqspinlock: Allow 1 lock stealing attempt Waiman Long
2015-10-15 22:51 ` [PATCH tip/locking/core v8 5/5] locking/pvqspinlock: Queue node adaptive spinning Waiman Long
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