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Date: Sun, 7 Jul 2013 11:59:07 +0800
From: Wang YanQing <udknight@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Chuansheng Liu <chuansheng.liu@intel.com>, mingo@kernel.org,
        peterz@infradead.org, jbeulich@suse.com, paulmck@linux.vnet.ibm.com,
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        srivatsa.bhat@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
        jun.zhang@intel.com, fengguang.wu@intel.com
Subject: Re: [PATCH V2] smp: Give WARN()ing when calling
 smp_call_function_many()/single() in serving irq
Message-ID: <20130707035907.GA2875@udknight>
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On Fri, Jul 05, 2013 at 04:37:14PM +0200, Thomas Gleixner wrote:
> Hmm, even there it matters, because of the following scenario:
> 
> CPU 0
> smp_call_function_single(CPU 1)
>     csd_lock(CPU 1)

No, smpl_call_function_single(CPU 1)
will csd_lock(CPU 0), not csd_lock(CPU 1)

>     irq_enter()
>     irq_exit()
>     __do_softirq()
>     smp_call_function_many()
>       setup csd (CPU 1)
>         csd_lock(CPU 1) ==> CPU 0 deadlocked itself.
> 

maybe below is the scenario:
     irq_enter()
     irq_exit()
     __do_softirq()
     smp_call_function_single()
       setup csd (CPU 1)
         csd_lock(CPU 0) ==> CPU 0 deadlocked itself.
 

> And this is even more likely to happen than the lock issue.
> 
> Thanks,
> 
> 	tglx
> --
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