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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, akpm@linux-foundation.org,
	mina86@mina86.org, 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
Date: Sun, 7 Jul 2013 10:41:13 +0800	[thread overview]
Message-ID: <20130707024113.GA2767@udknight> (raw)
In-Reply-To: <alpine.DEB.2.02.1307051548430.32106@ionos.tec.linutronix.de>

On Fri, Jul 05, 2013 at 03:50:57PM +0200, Thomas Gleixner wrote:
> On Sat, 16 Feb 2013, Chuansheng Liu wrote:
> > There is a real case for softirq DEADLOCK case:
> > 
> > CPUA                            CPUB
> >                                 spin_lock(&spinlock)
> >                                 Any irq coming, call the irq handler
> >                                 irq_exit()
> > spin_lock_irq(&spinlock)
> > <== Blocking here due to
> > CPUB hold it
> >                                   __do_softirq()
> >                                     run_timer_softirq()
> >                                       timer_cb()
> >                                         call smp_call_function_many()
> >                                           send IPI interrupt to CPUA
> >                                             wait_csd()
> > 
> > Then both CPUA and CPUB will be deadlocked here.
> 

Why can't we just use spin_lock_irq instead of spin_lock in CPUB to
prevent this to happen ?

And the according senario for kernel/smp.c is to use raw_spin_lock_irqsave
instead of raw_spin_lock in generic_smp_call_function_single_interrupt
to protect the follow one line codes:

        raw_spin_lock(&q->lock);
        list_replace_init(&q->list, &list);
        raw_spin_unlock(&q->lock);

Thanks.

      parent reply	other threads:[~2013-07-07  2:41 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-06 15:18 [PATCH] smp: give WARN in case of in_interrupt() when calling smp_call_function_many/single Chuansheng Liu
2013-02-06 13:42 ` [tip:core/locking] smp: Give WARN()ing if in_interrupt() when calling smp_call_function_many()/single() tip-bot for Chuansheng Liu
2013-02-11 12:20 ` [tip:core/locking] Revert "smp: Give WARN()ing if in_interrupt() when calling smp_call_function_many()/single()" tip-bot for Ingo Molnar
2013-02-16  5:26   ` Liu, Chuansheng
2013-02-16 13:57 ` [PATCH] smp: Give WARN()ing when calling smp_call_function_many()/single() in serving irq Chuansheng Liu
2013-02-16 14:10   ` [PATCH V2] " Chuansheng Liu
2013-02-18  1:38     ` Fengguang Wu
2013-02-19 23:01       ` Andrew Morton
2013-02-20  1:06         ` Fengguang Wu
2013-02-20  1:22           ` Liu, Chuansheng
2013-02-27 14:50     ` Lai Jiangshan
2013-03-01  3:37       ` Liu, Chuansheng
2013-08-05 22:46         ` Andrew Morton
2013-07-05 13:50     ` Thomas Gleixner
2013-07-05 14:37       ` Thomas Gleixner
2013-07-07  3:59         ` Wang YanQing
2013-07-07 13:47           ` Thomas Gleixner
2013-12-06  1:29         ` Max Filippov
2013-12-06 14:02           ` Thomas Gleixner
2013-12-06 18:31             ` Max Filippov
2013-07-07  2:41       ` Wang YanQing [this message]

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