Re: [PATCH v3] PCI: pci_call_probe: call local_pci_probe() when selected cpu is offline

[Hongchen Zhang]

Hi Ethan,
On 2024/7/22 PM 3:39, Ethan Zhao wrote:
> On 6/13/2024 3:42 PM, Hongchen Zhang wrote:
> > Call work_on_cpu(cpu, fn, arg) in pci_call_probe() while the argument
> > @cpu is a offline cpu would cause system stuck forever.
> >
> > This can be happen if a node is online while all its CPUs are
> > offline (We can use "maxcpus=1" without "nr_cpus=1" to reproduce it).
> >
> > So, in the above case, let pci_call_probe() call local_pci_probe()
> > instead of work_on_cpu() when the best selected cpu is offline.
> >
> > Fixes: 69a18b18699b ("PCI: Restrict probe functions to housekeeping 
> > CPUs")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > Signed-off-by: Hongchen Zhang <zhanghongchen@xxxxxxxxxxx>
> > ---
> > v2 -> v3: Modify commit message according to Markus's suggestion
> > v1 -> v2: Add a method to reproduce the problem
> > ---
> >   drivers/pci/pci-driver.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index af2996d0d17f..32a99828e6a3 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -386,7 +386,7 @@ static int pci_call_probe(struct pci_driver *drv, 
> > struct pci_dev *dev,
> >           free_cpumask_var(wq_domain_mask);
> >       }
> > -    if (cpu < nr_cpu_ids)
>
> Why not choose the right cpu to callwork_on_cpu() ? the one that is 
> online. Thanks, Ethan
Yes, let housekeeping_cpumask() return online cpu is a good idea, but it 
may be changed by command line. so the simplest way is to call 
local_pci_probe when the best selected cpu is offline.
> > +    if ((cpu < nr_cpu_ids) && cpu_online(cpu))
> >           error = work_on_cpu(cpu, local_pci_probe, &ddi);
> >       else
> >           error = local_pci_probe(&ddi);


--
Best Regards
Hongchen Zhang