From: David Miller <davem@davemloft.net>
To: liuxiang_1999@126.com
Cc: liu.xiang6@zte.com.cn, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] net: davicom: dm9000: Avoid spinlock recursion during dm9000_timeout routine
Date: Wed, 18 Apr 2018 13:35:39 -0400 (EDT) [thread overview]
Message-ID: <20180418.133539.1514284482902646647.davem@davemloft.net> (raw)
In-Reply-To: <72770aae.bb31.162d9036874.Coremail.liuxiang_1999@126.com>
From: liuxiang <liuxiang_1999@126.com>
Date: Wed, 18 Apr 2018 21:48:22 +0800 (CST)
> Because the timeout task gets the main spinlock and disable the
> current cpu's irq, there is no other task on the same cpu can run,
> and tasks on the other cpus can not enter the dm9000_timeout()
> again. So in the whole dm9000_timeout() routine, db->timeout_cpu can
> not be changed by other tasks. Although smp_processor_id() may
> change after preempt_enable(), these tasks always get the false
> result when call dm9000_current_in_timeout. Only the timeout task
> get the true result. And if there is no timeout, all the tasks that
> want to do asynchronous phy operation get the false result. So I
> think this can avoid racy.
This is a very shaky foundation upon which to base the correctness
of your driver's synchronization in my opinion.
prev parent reply other threads:[~2018-04-18 17:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-14 8:50 [PATCH v3] net: davicom: dm9000: Avoid spinlock recursion during dm9000_timeout routine Liu Xiang
2018-04-16 15:05 ` David Miller
2018-04-18 13:48 ` liuxiang
2018-04-18 17:35 ` David Miller [this message]
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