Re: [PATCH] device probe: add self triggered delayed work request

From	Qing Huang <qing.huang@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] device probe: add self triggered delayed work request
Date	2016-08-09 23:00 +0200
Message-ID	<s4mhX-437-5@gated-at.bofh.it> (permalink)
References	<s3Qi5-e1-13@gated-at.bofh.it> <s42Mh-8w3-1@gated-at.bofh.it> <s4ciB-6ek-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 08/09/2016 03:11 AM, Shamir Rabinovitch wrote:
> On Mon, Aug 08, 2016 at 05:10:05PM -0700, Qing Huang wrote:
>> Not sure if I understood your scenario. Why there is a deadlock here?
>>
>   CPU0                                                   | CPU1
> ---------------------------------------------------------------------------------------------
>   driver_deferred_probe_add                              | driver_deferred_probe_trigger_wrapper
>    mutex_lock(&deferred_probe_mutex)                     |  driver_deferred_probe_trigger
>     cancel_delayed_work(&deferred_probe_trigger_work)    |   mutex_lock(&deferred_probe_mutex)
>      wait for "driver_deferred_probe_trigger_wrapper"    |    wait for "deferred_probe_mutex"
>
> is this possible scenario with this patch?
>
> if yes then CPU0 will wait for CPU1 to finish the delayed work whith
> mutex deferred_probe_mutex held while CPU1 will try to finish the
> delayed work and will wait for the same mutex forever.

CPU0 will not wait for "driver_deferred_probe_trigger_wrapper" to 
finish, it simply puts the work request onto the queue and returns.

Qing

>
> it seems like dead lock scenario to me.
>
> please say if this scenario is possible.
>
> BR, Shamir Rabinovitch

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Re: [PATCH] device probe: add self triggered delayed work request Shamir Rabinovitch <shamir.rabinovitch@oracle.com> - 2016-08-08 12:50 +0200
  Re: [PATCH] device probe: add self triggered delayed work request Qing Huang <qing.huang@oracle.com> - 2016-08-09 02:10 +0200
    Re: [PATCH] device probe: add self triggered delayed work request Shamir Rabinovitch <shamir.rabinovitch@oracle.com> - 2016-08-09 12:20 +0200
      Re: [PATCH] device probe: add self triggered delayed work request Qing Huang <qing.huang@oracle.com> - 2016-08-09 23:00 +0200

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