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

[Junxiao Bi]

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.

Thanks,

Junxiao.

> Thanks,
> Song
>
> [...]