Re: Race condition between driver_probe_device and device_shutdown‏

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Wed, 23 May 2012, Ming Lei wrote:

> >> Do you think that a buggy driver should be able to prevent the system
> >> from shutting down?
> 
> IMO, the buggy driver should be fixed first, not only in .probe or .release, but
> also in .runtime_resume, all may affect shutting down.
> 
> >
> > The original intent of the shutdown callback was to just the hardware
> > part of the device shutdown and not do muck with kernel data structures
> > because just the device portion should be more reliable and was all
> > that is needed.
> 
> The .shutdown callback pointer is got from device->driver, which is
> changed in probe and release path. Also runtime PM thing has been
> involved into shutting down recently, so looks not only hardware parts
> are involved now.

This is a tricky question.  Overall I think you're probably right.  

It's certainly true that holding the device lock across the shutdown
callback is the easiest and most reliable way to prevent these races.

Alan Stern

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