From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
x86@kernel.org, Zhenzhong Duan <zhenzhong.duan@oracle.com>,
James Morse <james.morse@arm.com>,
SRINIVAS <srinivas.eeda@oracle.com>
Subject: Re: [PATCH 1/5] locking/qspinlock: Safely handle > 4 nesting levels
Date: Tue, 22 Jan 2019 05:44:19 +0000 [thread overview]
Message-ID: <20190122054417.GC6445@brain-police> (raw)
In-Reply-To: <20190121091234.GG27931@hirez.programming.kicks-ass.net>
On Mon, Jan 21, 2019 at 10:12:34AM +0100, Peter Zijlstra wrote:
> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
> index 8a8c3c208c5e..983b49a75826 100644
> --- a/kernel/locking/qspinlock.c
> +++ b/kernel/locking/qspinlock.c
> @@ -412,6 +412,12 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
> idx = node->count++;
> tail = encode_tail(smp_processor_id(), idx);
>
> + if (idx >= MAX_NODES) {
> + while (!queued_spin_trylock(lock))
> + cpu_relax();
> + goto release;
> + }
> +
> node = grab_mcs_node(node, idx);
With an unlikely() and a comment, I /much/ prefer this approach!
Will
next prev parent reply other threads:[~2019-01-22 5:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-21 2:49 [PATCH 0/5] locking/qspinlock: Safely handle > 4 nesting levels Waiman Long
2019-01-21 2:49 ` [PATCH 1/5] " Waiman Long
2019-01-21 9:12 ` Peter Zijlstra
2019-01-21 13:13 ` Waiman Long
2019-01-22 5:44 ` Will Deacon [this message]
2019-01-21 2:49 ` [PATCH 2/5] locking/qspinlock_stat: Track the no MCS node available case Waiman Long
2019-01-21 2:49 ` [PATCH 3/5] locking/qspinlock_stat: Separate out the PV specific stat counts Waiman Long
2019-01-21 2:49 ` [PATCH 4/5] locking/qspinlock_stat: Allow QUEUED_LOCK_STAT for all archs Waiman Long
2019-01-21 2:49 ` [PATCH 5/5] locking/qspinlock: Add some locking debug code Waiman Long
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