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

[Paul Cercueil]

Hi Sergei,


Le sam. 23 janv. 2021 à 19:41, Sergei Shtylyov 
<sergei.shtylyov@xxxxxxxxx> a écrit :
> 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. :-)

Oops. Hopefully Bin or Greg can fix it when merging (if I don't need to 
v2, that is to say - feedback welcome).

Cheers,
-Paul

> >  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@xxxxxxxxxxxxxxx # v4.9+
> >  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  Reviewed-by: Tony Lindgren <tony@xxxxxxxxxxx>
> >  Tested-by: Tony Lindgren <tony@xxxxxxxxxxx>
> [...]
>
>
> MBR, Sergei