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

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Date:	Mon, 8 Aug 2016 13:42:51 +0300
From:	Shamir Rabinovitch <shamir.rabinovitch@...cle.com>
To:	Qing Huang <qing.huang@...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, shamir.rabinovitch@...cle.com
Subject: Re: [PATCH] device probe: add self triggered delayed work request

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!>

Please confirm if this scenario is possible.

BR, Shamir Rabinovitch