netdev - Re: [PATCH v3] rfkill: Add rfkill-any LED trigger

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Date:   Mon, 02 Jan 2017 12:12:13 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Michał Kępień <kernel@...pniu.pl>,
        "David S . Miller" <davem@...emloft.net>
Cc:     Михаил Кринкин 
        <krinkin.m.u@...il.com>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] rfkill: Add rfkill-any LED trigger


>   - Handle the global mutex properly when rfkill_set_{hw,sw}_state()
> or
>     rfkill_set_states() is called from within an rfkill callback.  v2
>     always tried to lock the global mutex in such a case, which led
> to a
>     deadlock when an rfkill driver called one of the above functions
>     from its query or set_block callback.  This is solved by defining
> a
>     new bitfield, RFKILL_BLOCK_SW_HASLOCK, which is set before the
> above
>     callbacks are invoked and cleared afterwards; the functions
> listed
>     above use this bitfield to tell rfkill_any_led_trigger_event()
>     whether the global mutex is currently held or not.
>     RFKILL_BLOCK_SW_SETCALL cannot be reused for this purpose as
> setting
>     it before invoking the query callback would cause any calls to
>     rfkill_set_sw_state() made from within that callback to work on
>     RFKILL_BLOCK_SW_PREV instead of RFKILL_BLOCK_SW and thus change
> the
>     way rfkill_set_block() behaves.

I'm not super happy with this conditional locking - can't we instead
defer the necessary work to a workqueue, or so, for purposes of the
LED?

johannes