Re: [RE-RESEND PATCH 1/4] usb: musb: Fix runtime PM race in musb_queue_resume_work

[Sergei Shtylyov <sergei.shtylyov@gmail.com>]

On 1/23/21 5:24 PM, Paul Cercueil wrote:

> musb_queue_resume_work() would call the provided callback if the runtime
> PM status was 'active'. Otherwise, it would enqueue the request if the
> hardware was still suspended (musb->is_runtime_suspended is true).
> 
> This causes a race with the runtime PM handlers, as it is possible to be
> in the case where the runtime PM status is not yet 'active', but the
> hardware has been awaken (PM resume function has been called).

   Awakened. :-)

> When hitting the race, the resume work was not enqueued, which probably
> triggered other bugs further down the stack. For instance, a telnet
> connection on Ingenic SoCs would result in a 50/50 chance of a
> segmentation fault somewhere in the musb code.
> 
> Rework the code so that either we call the callback directly if
> (musb->is_runtime_suspended == 0), or enqueue the query otherwise.
> 
> Fixes: ea2f35c01d5e ("usb: musb: Fix sleeping function called from invalid context for hdrc glue")
> Cc: stable@vger.kernel.org # v4.9+
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> Reviewed-by: Tony Lindgren <tony@atomide.com>
> Tested-by: Tony Lindgren <tony@atomide.com>
[...]


MBR, Sergei