Re: [PATCH 02/33] PCI: Protect against concurrent change of housekeeping cpumask

[Frederic Weisbecker]

Le Mon, Sep 22, 2025 at 05:51:39PM -0400, Waiman Long a écrit :
> On 9/18/25 10:00 AM, Frederic Weisbecker wrote:
> > No the point is that I need to keep the target selection
> > (housekeeping_cpumask() read) and the work queue within the same
> > RCU critical section so that things are synchronized that way:
> > 
> >      CPU 0                                          CPU 1
> >      -----                                          -----
> >      rcu_read_lock()                                housekeeping_update()
> >      cpu = cpumask_any(housekeeping_cpumask(...))       housekeeping_cpumask &= ~val
> >      queue_work_on(cpu, pci_probe_wq, work)             synchronize_rcu()
> >      rcu_read_unlock()                                  flush_workqueue(pci_probe_wq)
> >      flush_work(work)
> > And I can't include the whole work_on_cpu() within rcu_read_lock() because
> > flush_work() may sleep.
> 
> Right, you are trying to avoid flush_work() within rcu_read_lock() critical
> section. It makes it easier to review if you mention that in the commit log.

Good point!

> 
> > 
> > Also now that you mention it, I need to create that pci_probe_wq and flush it :-)
> 
> OK, another wq :-)

Yeah I know :-s

> 
> Cheers,
> Longman
> 

-- 
Frederic Weisbecker
SUSE Labs