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Subject: Re: [PATCH] device probe: add self triggered delayed work request
To: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
References: <20160808104250.GA12480@shamir-linux.uk.oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Grant Likely <grant.likely@linaro.org>,
        Santosh Shilimkar <santosh.shilimkar@oracle.com>,
        linux-kernel@vger.kernel.org
From: Qing Huang <qing.huang@oracle.com>
Message-ID: <57A91F5D.1060605@oracle.com>
Date: Mon, 8 Aug 2016 17:10:05 -0700
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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