Re: [bug report] lockdep WARN at PCI device rescan

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Nov 14, 2023 at 04:57:01PM +0100, Lukas Wunner wrote:
> On Tue, Nov 14, 2023 at 02:04:34PM +0200, Andy Shevchenko wrote:
> > On Tue, Nov 14, 2023 at 11:47:15AM +0100, Heiner Kallweit wrote:
> > > On 14.11.2023 11:16, Wolfram Sang wrote:
> > > > On Tue, Nov 14, 2023 at 06:54:29AM +0000, Shinichiro Kawasaki wrote:

...

> > > > > The lockdep splat indicates possible deadlock between
> > > > > pci_rescan_remove_lock and work_completion lock have deadlock
> > > > > possibility.
> > > > > In the call stack, I found that the workqueue thread for
> > > > > i801_probe() calls p2sb_bar(), which locks pci_rescan_remove_lock.
> > > 
> > > i801 just uses p2sb_bar(), I don't see any issue in i801. Root cause
> > > seems to be in the PCI subsystem. Calling p2sb_bar() from a PCI driver
> > > probe callback seems to be problematic, nevertheless it's a valid API
> > > usage.
> > 
> > So, currently I'm lack of (good) ideas and would like to hear other (more
> > experienced) PCI developers on how is to address this...
> 
> Can you add a p2sb_bar_locked() library call which is used by the
> i801 probe path?
> 
> Basically rename p2sb_bar() to __p2sb_bar() and add a third parameter
> of type boolean which signifies whether it's invoked in locked context
> or not, then call that from p2sb_bar() and p2sb_bar_locked() wrappers.

It may work, I assume. Let me cook the patch.

-- 
With Best Regards,
Andy Shevchenko