Re: [dm-devel] [PATCH -next v2 2/6] md: refactor action_store() for 'idle' and 'frozen'

[Yu Kuai]

Hi,

在 2023/06/13 20:25, Xiao Ni 写道:
> On Tue, Jun 13, 2023 at 8:00 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > 在 2023/06/13 16:02, Xiao Ni 写道:
> > > 在 2023/5/29 下午9:20, Yu Kuai 写道:
> > > > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> > > >
> > > > Prepare to handle 'idle' and 'frozen' differently to fix a deadlock,
> > > > there
> > > > are no functional changes except that MD_RECOVERY_RUNNING is checked
> > > > again after 'reconfig_mutex' is held.
> > >
> > >
> > > Can you explain more about why it needs to check MD_RECOVERY_RUNNING
> > > again here?
> >
> > As I explain in the following comment:
>
> Hi
>
> Who can clear the flag before the lock is held?

Basically every where that can clear the flag...

// This context 	// Other context
			mutex_lock
			...
test_bit -> pass
			clear_bit
			mutex_unlock
mutex_lock
test_bit -> check again

Thanks,
Kuai
> Regards
> Xiao
> > > > +    /*
> > > > +     * Check again in case MD_RECOVERY_RUNNING is cleared before lock is
> > > > +     * held.
> > > > +     */
> > > > +    if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
> > > > +        mddev_unlock(mddev);
> > > > +        return;
> > > > +    }
> >
> > Thanks,
> > Kuai
>
> .