Re: mhi resume failure on reboot with 6.13-rc2

[Johan Hovold <johan@kernel.org>]

On Wed, Dec 18, 2024 at 06:00:19PM +0530, Manivannan Sadhasivam wrote:
> On Wed, Dec 18, 2024 at 01:02:39PM +0100, Johan Hovold wrote:
> > On Wed, Dec 18, 2024 at 05:08:30PM +0530, Manivannan Sadhasivam wrote:
> > > On Wed, Dec 18, 2024 at 09:40:45AM +0100, Johan Hovold wrote:
> > 
> > > > I've tracked down the hang to a deadlock on the parent device lock.
> > > > 
> > > > Driver core takes the parent device lock before calling shutdown(), and
> > > > then mhi_pci_shutdown() waits indefinitely for the recovery thread to
> > > > finish.
> > 
> > > Thanks for tracking the deadlock. I think we should use pci_try_reset_function()
> > > instead of pci_reset_function() in mhi_pci_recovery_work().
> > > 
> > > If the pci_dev_lock() is already taken, it will return with -EAGAIN and we do
> > > not need to worry in that case since the host is going to be powered off anyway
> > > (and so the device).
> > 
> > That may work. But note that I've now also seen this deadlock during
> > suspend (i.e. when the device is not going away). The
> > pci_try_reset_function() should avoid the deadlock here too, but we'll
> > end up in funny state.
> 
> Hopefully, recovery_work() started by mhi_pci_runtime_resume() would be able to
> reset the device.

But that's not going to happen as that reset is what is currently
causing the deadlock and which would simply be skipped if you switch to
pci_try_reset_function().

Johan