linux-kernel - Re: [PATCH] usb: cdc-acm: fix cooldown mechanism

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Date:   Tue, 20 Oct 2020 09:41:34 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Pascal Vizeli <pascal.vizeli@...ucasa.com>
Subject: Re: [PATCH] usb: cdc-acm: fix cooldown mechanism

Am Montag, den 19.10.2020, 19:07 +0200 schrieb Jerome Brunet:
> Commit a4e7279cd1d1 ("cdc-acm: introduce a cool down") is causing
> regression if there is some USB error, such as -EPROTO.
> 
> This has been reported on some samples of the Odroid-N2 using the Combee II
> Zibgee USB dongle.
> 
> > struct acm *acm = container_of(work, struct acm, work)
> 
> is incorrect in case of a delayed work and causes warnings, usually from
> the workqueue:
> 
> > WARNING: CPU: 0 PID: 0 at kernel/workqueue.c:1474 __queue_work+0x480/0x528.
> 
> When this happens, USB eventually stops working completely after a while.
> Also the ACM_ERROR_DELAY bit is never set, so the cooldown mechanism
> previously introduced cannot be triggered and acm_submit_read_urb() is
> never called.
> 
> This changes makes the cdc-acm driver use a single delayed work, fixing the
> pointer arithmetic in acm_softint() and set the ACM_ERROR_DELAY when the
> cooldown mechanism appear to be needed.
> 
> Fixes: a4e7279cd1d1 ("cdc-acm: introduce a cool down")
> Reported-by: Pascal Vizeli <pascal.vizeli@...ucasa.com>
> Cc: Oliver Neukum <oneukum@...e.com>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
Acked-by: Oliver Neukum <oneukum@...e.com>