From: Peter Zijlstra <peterz@infradead.org>
To: Alex Kogan <alex.kogan@oracle.com>
Cc: linux-arch@vger.kernel.org, guohanjun@huawei.com, arnd@arndb.de,
dave.dice@oracle.com, jglauber@marvell.com, x86@kernel.org,
will.deacon@arm.com, linux@armlinux.org.uk,
steven.sistare@oracle.com, linux-kernel@vger.kernel.org,
rahul.x.yadav@oracle.com, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, longman@redhat.com, tglx@linutronix.de,
daniel.m.jordan@oracle.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 2/5] locking/qspinlock: Refactor the qspinlock slow path
Date: Tue, 16 Jul 2019 17:58:39 +0200 [thread overview]
Message-ID: <20190716155839.GF3402@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <9D5B6F33-6003-4CCA-BBE5-998B5A679B9C@oracle.com>
On Tue, Jul 16, 2019 at 10:53:02AM -0400, Alex Kogan wrote:
> On Jul 16, 2019, at 6:20 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Mon, Jul 15, 2019 at 03:25:33PM -0400, Alex Kogan wrote:
> >
> >> +/*
> >> + * set_locked_empty_mcs - Try to set the spinlock value to _Q_LOCKED_VAL,
> >> + * and by doing that unlock the MCS lock when its waiting queue is empty
> >> + * @lock: Pointer to queued spinlock structure
> >> + * @val: Current value of the lock
> >> + * @node: Pointer to the MCS node of the lock holder
> >> + *
> >> + * *,*,* -> 0,0,1
> >> + */
> >> +static __always_inline bool __set_locked_empty_mcs(struct qspinlock *lock,
> >> + u32 val,
> >> + struct mcs_spinlock *node)
> >> +{
> >> + return atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL);
> >> +}
> >
> > That name is nonsense. It should be something like:
> >
> > static __always_inline bool __try_clear_tail(…)
>
> We already have set_locked(), so I was trying to convey the fact that we are
> doing the same here, but only when the MCS chain is empty.
>
> I can use __try_clear_tail() instead.
Thing is, we go into this function with: *,0,1 and are trying to obtain
0,0,1. IOW, we're trying to clear the tail, while preserving pending and
locked.
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next prev parent reply other threads:[~2019-07-16 15:59 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 19:25 [PATCH v3 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-07-15 19:25 ` [PATCH v3 1/5] locking/qspinlock: Make arch_mcs_spin_unlock_contended more generic Alex Kogan
2019-07-16 10:23 ` Peter Zijlstra
2019-07-15 19:25 ` [PATCH v3 2/5] locking/qspinlock: Refactor the qspinlock slow path Alex Kogan
2019-07-16 10:20 ` Peter Zijlstra
2019-07-16 14:53 ` Alex Kogan
2019-07-16 15:58 ` Peter Zijlstra [this message]
2019-07-15 19:25 ` [PATCH v3 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-07-15 21:30 ` Waiman Long
2019-07-16 11:04 ` Peter Zijlstra
2019-07-16 14:26 ` Alex Kogan
2019-07-16 14:44 ` Waiman Long
[not found] ` <aa73b86d-902a-bb6f-d372-8645c8299a6d@redhat.com>
[not found] ` <C1C55A40-FDB1-43B5-B551-F9B8BE776DF8@oracle.com>
2019-07-16 14:50 ` Waiman Long
2019-07-17 17:44 ` Alex Kogan
2019-07-17 17:58 ` Waiman Long
2019-07-16 11:05 ` Peter Zijlstra
2019-07-16 14:30 ` Alex Kogan
2019-07-16 15:50 ` Peter Zijlstra
2019-07-16 17:19 ` Alex Kogan
2019-07-16 18:47 ` Peter Zijlstra
2019-07-17 8:39 ` Peter Zijlstra
2019-07-17 8:59 ` Peter Zijlstra
2019-07-17 14:52 ` Alex Kogan
[not found] ` <FFC2D45A-24B3-40E1-ABBB-1D696E830B23@oracle.com>
2019-07-17 15:09 ` Peter Zijlstra
2019-07-17 2:16 ` Waiman Long
2019-07-17 7:44 ` Peter Zijlstra
2019-07-17 13:35 ` Waiman Long
2019-07-17 14:42 ` Alex Kogan
2019-07-15 19:25 ` [PATCH v3 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-07-16 15:59 ` Peter Zijlstra
2019-07-15 19:25 ` [PATCH v3 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2019-07-16 11:47 ` [PATCH v3 0/5] Add NUMA-awareness to qspinlock Nicholas Piggin
[not found] ` <7D29555E-8F72-4EDD-8A87-B1A59C3945A6@oracle.com>
2019-07-16 23:07 ` Nicholas Piggin
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