[Bug 221346] Bluetooth: btintel_pcie (8086:e476) may hang in shutdown path (synchronize_irq) during reboot stress test

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221346

--- Comment #6 from Zhang Zhigang (zhangzhigang1996@gmail.com) ---
I would like to provide more details about my system setup, as it may be
relevant to the shutdown hang issue.

My filesystem layout is non-standard. In addition to `/boot` and `/`, I have a
separate `/data` partition, and several key directories are bind-mounted from
it.

Current block layout:

* nvme0n1p1 → /boot
* nvme0n1p3 → / (root filesystem)
* nvme0n1p5 → /data

The `/data` partition contains subdirectories which are bind-mounted to
standard system paths:

* /data/home      → /home
* /data/var       → /var
* /data/local     → /usr/local
* /data/opt       → /opt

Example mount output:

```
aa [ ~ ]$ lsblk 
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
nvme0n1     259:0    0 476.9G  0 disk 
├─nvme0n1p1 259:1    0   511M  0 part /boot
├─nvme0n1p2 259:2    0  14.6G  0 part 
├─nvme0n1p3 259:3    0  19.5G  0 part /
├─nvme0n1p4 259:4    0  19.5G  0 part 
└─nvme0n1p5 259:5    0 422.7G  0 part /var
                                      /usr/local
                                      /opt
                                      /home
                                      /data
aa [ ~ ]$ mount | grep nvme
/dev/nvme0n1p3 on / type ext4 (rw,relatime,seclabel)
/dev/nvme0n1p1 on /boot type vfat
(rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro)
/dev/nvme0n1p5 on /data type ext4 (rw,relatime,seclabel)
/dev/nvme0n1p5 on /home type ext4 (rw,relatime,seclabel)
/dev/nvme0n1p5 on /opt type ext4 (rw,relatime,seclabel)
/dev/nvme0n1p5 on /usr/local type ext4 (rw,relatime,seclabel)
/dev/nvme0n1p5 on /var type ext4 (rw,relatime,seclabel)

aa [ ~ ]$ ls -a /data/
.  ..  home  local  opt  .swap.img  var
```



These mounts are managed via systemd `.mount` units .
Key characteristics:

1. `/data` is mounted early with `DefaultDependencies=no`
2. Other mount points (`/home`, `/var`, `/usr/local`, `/opt`) are bind mounts
with:

   * `BindsTo=data.mount`
   * `After=data.mount`
3. All mount units explicitly include:

   * `Conflicts=umount.target shutdown.target`
4. Additional ordering is enforced via:
   `/etc/systemd/system/sysinit.target.d/data-mount.conf`

This setup ensures that `/data` is mounted before other system paths and that
dependent mounts are tied to it.

```
cat >/etc/systemd/system/data.mount <<"EOF"
[Unit]
Description=Data Partition
DefaultDependencies=no

After=systemd-udevd.service
Before=systemd-journald.service sysinit.target local-fs.target

OnFailure=emergency.target
Conflicts=umount.target shutdown.target

[Mount]
What=/dev/disk/by-uuid/UUID
Where=/data
Type=ext4
Options=defaults

[Install]
WantedBy=local-fs.target
EOF

cat >/etc/systemd/system/home.mount <<"EOF"
[Unit]
Description=Bind /data/home → /home
DefaultDependencies=no

BindsTo=data.mount
After=data.mount
Before=sysinit.target local-fs.target
Conflicts=umount.target shutdown.target

[Mount]
What=/data/home
Where=/home
Type=none
Options=bind

[Install]
WantedBy=local-fs.target
EOF

cat >/etc/systemd/system/var.mount <<"EOF"
[Unit]
Description=Bind /data/var → /var
DefaultDependencies=no

BindsTo=data.mount
After=data.mount
Before=systemd-journald.service sysinit.target local-fs.target
Conflicts=umount.target shutdown.target

[Mount]
What=/data/var
Where=/var
Type=none
Options=bind

[Install]
WantedBy=local-fs.target
EOF

cat >/etc/systemd/system/usr-local.mount <<"EOF"
[Unit]
Description=Bind /data/local → /usr/local
DefaultDependencies=no

BindsTo=data.mount
After=data.mount
Before=sysinit.target local-fs.target
Conflicts=umount.target shutdown.target

[Mount]
What=/data/local
Where=/usr/local
Type=none
Options=bind

[Install]
WantedBy=local-fs.target
EOF

cat >/etc/systemd/system/opt.mount <<"EOF"
[Unit]
Description=Bind /data/opt → /opt
DefaultDependencies=no

BindsTo=data.mount
After=data.mount
Before=sysinit.target local-fs.target
Conflicts=umount.target shutdown.target

[Mount]
What=/data/opt
Where=/opt
Type=none
Options=bind

[Install]
WantedBy=local-fs.target
EOF

mkdir -pv /etc/systemd/system/sysinit.target.d
cat >/etc/systemd/system/sysinit.target.d/data-mount.conf <<"EOF"
[Unit]
Requires=data.mount var.mount home.mount usr-local.mount opt.mount
After=data.mount var.mount home.mount usr-local.mount opt.mount
EOF
```

However, I suspect this layout might be contributing to the shutdown hang,
especially during the late unmount phase. Since multiple critical directories
(e.g. `/var`) are bind-mounted from a single filesystem, there may be ordering
or dependency issues when systemd tries to unmount them.

The issue still occurs intermittently and typically at a late stage of
shutdown, where logging is limited.

If this filesystem layout or mount configuration could potentially trigger such
behavior, I would appreciate any guidance on how to further debug or simplify
the setup for testing.

Thank you.

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