linux-kernel - Re: [PATCH] Revert "usb: core: remove local_irq

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Message-ID: <23aebb29-db6f-95fb-5cad-10d9b45fcd57@web.de>
Date:   Mon, 17 Jun 2019 12:12:19 +0200
From:   Soeren Moch <smoch@....de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Alan Stern <stern@...land.harvard.edu>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH] Revert "usb: core: remove local_irq_save() around
 ->complete() handler"



On 12.06.19 16:47, Sebastian Andrzej Siewior wrote:
> On 2019-06-12 10:38:11 [-0400], Alan Stern wrote:
>>> When stopping hostapd after it hangs:
>>> [  903.504475] ieee80211 phy0: rt2x00queue_flush_queue: Warning - Queue
>>> 14 failed to flush
>> Instead of reverting the original commit, can you prevent the problem 
>> by adding local_irq_save() and local_irq_restore() to the URB 
>> completion routines in that wireless driver?
>>
>> Probably people who aren't already pretty familiar with the driver code
>> won't easily be able to locate the race.  Still, a little overkill may
>> be an acceptable solution.
> Not from RT point of view because you do
> 	local_irq_save() -> spin_lock()
>
> but it might be worth checking if the local_irq_save() within that
> wireless driver avoids the race or not.
I just sent a patch for the underlying problem in the rt2x00 driver, see
[1].
So we can drop this patch here and keep RT folks happy.
I really hope that no other usb drivers are affected by similar problems.

Zyxel support just sent me (some?) source code for the firmware of my
internet router (my real problem I mentioned before). Need to look into
this...

Thanks for your help,
Soeren


[1] https://lkml.org/lkml/2019/6/17/238
>> Alan Stern
> Sebastian