Re: [PATCH] md: fix deadlock causing by sysfs_notify

[Junxiao Bi]

On 7/14/20 9:18 AM, Song Liu wrote:

> On Mon, Jul 13, 2020 at 11:41 PM Junxiao Bi <junxiao.bi@xxxxxxxxxx> wrote:
> > On 7/13/20 11:17 PM, Song Liu wrote:
> >
> > > On Thu, Jul 9, 2020 at 4:36 PM Junxiao Bi <junxiao.bi@xxxxxxxxxx> wrote:
> > > > The following deadlock was captured. The first process is holding 'kernfs_mutex'
> > > > and hung by io. The io was staging in 'r1conf.pending_bio_list' of raid1 device,
> > > > this pending bio list would be flushed by second process 'md127_raid1', but
> > > > it was hung by 'kernfs_mutex'. Using sysfs_notify_dirent_safe() to replace
> > > > sysfs_notify() can fix it. There were other sysfs_notify() invoked from io
> > > > path, removed all of them.
> > > [...]
> > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > Signed-off-by: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
> > > Thanks for the patch. It looks good in general. One question though, do we
> > > need the same change the following line in md.c:level_store()?
> > >
> > >       sysfs_notify(&mddev->kobj, NULL, "level");
> > Thanks for the review. This one is not in io path, looks it's safe. I
> > can change it if you want to align it with others.
> This one is the only leftover. Let's also change it.

Sure, i will send a v2.

Thanks,

Junxiao.

> Thanks,
> Song