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

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Message-ID: <57A91F5D.1060605@oracle.com>
Date:	Mon, 8 Aug 2016 17:10:05 -0700
From:	Qing Huang <qing.huang@...cle.com>
To:	Shamir Rabinovitch <shamir.rabinovitch@...cle.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	Santosh Shilimkar <santosh.shilimkar@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] device probe: add self triggered delayed work request



On 08/08/2016 03:42 AM, Shamir Rabinovitch wrote:
> Hi Qing,
>
> I suspect there is potential dead-lock with this patch:
>
> cpu0                                                    cpu1
>
> driver_deferred_probe_add                               deferred_probe_work_func
>   ...                                                     mutex_unlock(&deferred_probe_mutex)
>   mutex_lock(&deferred_probe_mutex)                        bus_probe_device(dev)
>    ...                                                      device return -EPROBE_DEFER
>    ...                                                       driver_deferred_probe_add
>    ...                                                        mutex_lock(&deferred_probe_mutex)
>    ...                                                         <deadlock!>
>    cancel_delayed_work(&deferred_probe_trigger_work)
>     <work will never end - deadlock!>
Not sure if I understood your scenario. Why there is a deadlock here?

>
> Please confirm if this scenario is possible.
>
> BR, Shamir Rabinovitch