Re: [PATCH] PCI: Fix AB-BA deadlock between aer_isr() and device_shutdown()

[duziming]

在 2026/1/14 2:51, Bjorn Helgaas 写道:
> On Fri, Jan 09, 2026 at 05:56:03PM +0800, Ziming Du wrote:
> > During system shutdown, a deadlock may occur between AER recovery process
> > and device shutdown as follows:
> >
> > The device_shutdown path holds the device_lock throughout the entire
> > process and waits for the irq handlers to complete when release nodes:
> >
> >    device_shutdown
> >      device_lock                      # A hold device_lock
> >      pci_device_shutdown
> >        pcie_port_device_remove
> >          remove_iter
> >            device_unregister
> >              device_del
> >                bus_remove_device
> >                  device_release_driver
> >                    devres_release_all
> >                      release_nodes    # B wait for irq handlers
> Can you add the wait location to these example?  release_nodes()
> doesn't wait itself, so I guess it must be in a dr->node.release()
> function?
>
> And I guess it must be related to something in the IRQ path that is
> held while aer_isr() runs?

When releasing the interrupt resources, the process eventually calls 
free_irq(), and then

__synchronize_irq () will be called to wait until all irq handlers have 
finished.

> > The aer_isr path will acquire device_lock in pci_bus_reset():
> >
> >    aer_isr                            # B execute irq process
> >      aer_isr_one_error
> >        aer_process_err_devices
> >          handle_error_source
> >            pcie_do_recovery
> >            aer_root_reset
> >              pci_bus_error_reset
> >                pci_bus_reset          # A acquire device_lock
> >
> > The circular dependency causes system hang. Fix it by using
> > pci_bus_trylock() instead of pci_bus_lock() in pci_bus_reset(). When the
> > lock is unavailable, return -EAGAIN, as in similar cases.
> pci_bus_error_reset() may use either pci_slot_reset() or
> pci_bus_reset(), and this patch addresses only pci_bus_reset().  Is
> the same deadlock possible in the pci_slot_reset() path?

Looking at the code flow, I agree that there is likely a potential issue 
here.

Unfortunately, my current test environment does not support slot_reset, so

I haven't been able to reproduce this specific scenario locally. It would be

incredibly helpful if someone with a compatible setup could help verify 
or reproduce this behavior.

> > Fixes: c4eed62a2143 ("PCI/ERR: Use slot reset if available")
> > Signed-off-by: Ziming Du <duziming2@xxxxxxxxxx>
> > ---
> >   drivers/pci/pci.c | 17 ++++++++++++-----
> >   1 file changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 13dbb405dc31..7471bfa6f32e 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -5515,15 +5515,22 @@ static int pci_bus_reset(struct pci_bus *bus, bool probe)
> >   	if (probe)
> >   		return 0;
> >   
> > -	pci_bus_lock(bus);
> > +	/*
> > +	 * Replace blocking lock with trylock to prevent deadlock during bus reset.
> > +	 * Same as above except return -EAGAIN if the bus cannot be locked.
> Wrap this to fit in 80 columns like the rest of the file.
>
> > +	 */
> > +	if (pci_bus_trylock(bus)) {
> >   
> > -	might_sleep();
> > +		might_sleep();
> >   
> > -	ret = pci_bridge_secondary_bus_reset(bus->self);
> > +		ret = pci_bridge_secondary_bus_reset(bus->self);
> >   
> > -	pci_bus_unlock(bus);
> > +		pci_bus_unlock(bus);
> >   
> > -	return ret;
> > +		return ret;
> > +	}
> > +
> > +	return -EAGAIN;
> >   }
> >   
> >   /**
> > --
> > 2.43.0