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From: Christoph Paasch <christoph.paasch@uclouvain.be>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: g@neilslaptop.think-freely.org,
	Bart Van Assche <bvanassche@acm.org>,
	David Miller <davem@davemloft.net>,
	netdev@vger.kernel.org
Subject: Re: [PATCH RFC] spinlock: split out debugging check from spin_lock_mutex
Date: Thu, 11 Apr 2013 19:51:20 +0200	[thread overview]
Message-ID: <3142935.JcJEKt2WmH@cpaasch-mac> (raw)
In-Reply-To: <20130411170404.GE8986@neilslaptop.think-freely.org>

On Thursday 11 April 2013 13:04:05 Neil Horman wrote:
> I dont believe the deadlock you describe can happen.  The spin_lock_mutex
> operation disables irqs on the local cpu with local_irq_save, so we won't
> loose the cpu while we're holding the spinlock.  Likewise we don't restore
> the irq flags until after we release said lock.  Once we have the mutex, if
> we're preempted by another path that goes through the netpoll_poll_dev
> path, then we hit the trylock api call.  The spinlock is either released or
> held on another cpu (read: no deadlock), and if the mutex is held, then the
> trylock simply fails.

Thanks for explaining this to me. I was looking for a local_bh_disable() - but 
local_irq_save does the job too.


Thanks,
Christoph

-- 
IP Networking Lab --- http://inl.info.ucl.ac.be
MultiPath TCP in the Linux Kernel --- http://multipath-tcp.org
UCLouvain
--

  reply	other threads:[~2013-04-11 17:51 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-11 13:42 Netpoll triggers soft lockup Bart Van Assche
2013-04-11 14:08 ` Neil Horman
2013-04-11 15:18 ` [PATCH RFC] spinlock: split out debugging check from spin_lock_mutex Neil Horman
2013-04-11 15:54   ` Christoph Paasch
2013-04-11 17:04     ` Neil Horman
2013-04-11 17:51       ` Christoph Paasch [this message]
2013-04-11 15:57   ` Eric Dumazet
2013-04-11 16:56     ` Neil Horman
2013-04-11 17:31   ` Bart Van Assche
2013-04-11 17:52     ` Neil Horman
2013-04-11 19:14     ` Neil Horman
2013-04-12  6:27       ` Bart Van Assche
2013-04-12 11:32         ` Neil Horman
2013-04-12 14:01           ` Bart Van Assche
2013-04-12 18:45             ` Neil Horman
2013-04-13  7:35               ` Bart Van Assche
2013-04-13 12:03                 ` Neil Horman
2013-04-15 14:16                 ` Neil Horman
     [not found]                   ` <CAO+b5-oBfH3M0dnrQSs-p1BF_5hKy2tsU-dD=EP9+S=iqPs5ew@mail.gmail.com>
2013-04-16 17:24                     ` Neil Horman
2013-04-18 19:29                       ` Neil Horman
2013-04-22 20:12                         ` Neil Horman
     [not found]                           ` <CAO+b5-r5jVJNZWuREUH5MQ3baeSPR8fVV1p9pMnukmiZd9nRhg@mail.gmail.com>
2013-04-23 13:23                             ` Neil Horman
     [not found]                               ` <CAO+b5-rQPyO9QE9v+oQTeo+G-ftcsehSB5=63AZ13QW4EJ1X0Q@mail.gmail.com>
2013-04-23 13:44                                 ` Neil Horman
2013-04-23 17:33                                   ` David Miller
2013-04-23 17:50                                     ` Neil Horman
2013-04-27 18:53                                       ` bvba Bart Van Assche
2013-04-29 18:13                                         ` Neil Horman
2013-04-29 19:12                                           ` Bart Van Assche
2013-04-30 15:35                                           ` [PATCH RFC] netpoll: convert mutex into a semaphore Neil Horman
2013-05-01 19:00                                             ` David Miller
2013-05-01 19:34                                               ` Neil Horman
2013-04-19  8:38             ` [PATCH RFC] spinlock: split out debugging check from spin_lock_mutex Ingo Molnar
2013-04-19 12:52               ` Neil Horman
2013-04-28  2:34 Neil Horman

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