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

[Qing Huang]

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