From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Daniel Walker <dwalker@mvista.com>
Cc: mingo@elte.hu, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] RT: Checks for cmpxchg in get_task_struct_rcu()
Date: Thu, 22 Sep 2005 15:05:37 +1000 [thread overview]
Message-ID: <43323BA1.6000100@yahoo.com.au> (raw)
In-Reply-To: <1127364629.8950.6.camel@c-67-188-6-232.hsd1.ca.comcast.net>
Daniel Walker wrote:
> +#else
> + raw_local_irq_disable();
> + oldusage = atomic_read(&t->usage);
> + if (oldusage == 0) {
> + raw_local_irq_enable();
> + return 0;
> + }
Isn't this still racy if another cpu drops the last reference
to task struct here? Or can't that happen?
When you said "disable preempt", I had some silly idea that this
function was only used in PREEMPT_RT mode, and that you would
simply disallow architectures without cmpxchg from configuring
PREEMPT_RT.
> + atomic_inc(&t->usage);
> + raw_local_irq_enable();
> +#endif
--
SUSE Labs, Novell Inc.
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next prev parent reply other threads:[~2005-09-22 5:04 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-21 23:37 [PATCH] RT: Checks for cmpxchg in get_task_struct_rcu() Daniel Walker
2005-09-22 0:59 ` Nick Piggin
2005-09-22 2:18 ` Daniel Walker
2005-09-22 3:27 ` Nick Piggin
2005-09-22 4:50 ` Daniel Walker
2005-09-22 5:05 ` Nick Piggin [this message]
2005-09-26 6:25 ` Ingo Molnar
2005-09-26 14:44 ` Daniel Walker
2005-09-26 6:26 ` Ingo Molnar
2005-09-26 6:39 ` Nick Piggin
2005-09-26 6:48 ` Ingo Molnar
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