From: Peter Zijlstra <peterz@infradead.org>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Alex Shi <alex.shi@intel.com>, Andi Kleen <andi@firstfloor.org>,
Michel Lespinasse <walken@google.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Matthew R Wilcox <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Rik van Riel <riel@redhat.com>,
Peter Hurley <peter@hurleysoftware.com>,
linux-kernel@vger.kernel.org, linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH v2 5/5] rwsem: do optimistic spinning for writer lock acquisition
Date: Wed, 26 Jun 2013 14:53:38 +0200 [thread overview]
Message-ID: <20130626125338.GK28407@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1372116051.22432.95.camel@schen9-DESK>
On Mon, Jun 24, 2013 at 04:20:51PM -0700, Tim Chen wrote:
> +#ifdef CONFIG_RWSEM_SPIN_ON_WRITE_OWNER
> +static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
> +{
> + int retval;
> + task_struct *owner;
> +
> + rcu_read_lock();
> + owner = sem->owner;
That wants to be: owner = ACCESS_ONCE(sem->owner);
> +
> + /* Spin only if active writer running */
> + if (owner)
> + retval = owner->on_cpu;
> + else
> + retval = false;
> +
> + rcu_read_unlock();
> + /*
> + * if lock->owner is not set, the sem owner may have just acquired
> + * it and not set the owner yet, or the sem has been released, or
> + * reader active.
> + */
> + return retval;
> +}
prev parent reply other threads:[~2013-06-26 15:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1372112541.git.tim.c.chen@linux.intel.com>
2013-06-24 23:20 ` [PATCH v2 1/5] rwsem: check the lock before cpmxchg in down_write_trylock Tim Chen
2013-06-24 23:20 ` [PATCH v2 2/5] rwsem: remove 'out' label in do_wake Tim Chen
2013-06-24 23:20 ` [PATCH v2 3/5] rwsem: remove try_reader_grant label do_wake Tim Chen
2013-06-24 23:20 ` [PATCH v2 4/5] rwsem/wake: check lock before do atomic update Tim Chen
2013-06-24 23:20 ` [PATCH v2 5/5] rwsem: do optimistic spinning for writer lock acquisition Tim Chen
2013-06-26 12:53 ` Peter Zijlstra [this message]
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