[PATCH v8 3/4] driver core: shut down devices asynchronously

[Nathan Chancellor]

Hi Stuart,

On Thu, Aug 22, 2024 at 03:28:04PM -0500, Stuart Hayes wrote:
> Add code to allow asynchronous shutdown of devices, ensuring that each
> device is shut down before its parents & suppliers.
> 
> Only devices with drivers that have async_shutdown_enable enabled will be
> shut down asynchronously.
> 
> This can dramatically reduce system shutdown/reboot time on systems that
> have multiple devices that take many seconds to shut down (like certain
> NVMe drives). On one system tested, the shutdown time went from 11 minutes
> without this patch to 55 seconds with the patch.
> 
> Signed-off-by: Stuart Hayes <stuart.w.hayes at gmail.com>
> Signed-off-by: David Jeffery <djeffery at redhat.com>

I am noticing several QEMU machines hang while shutting down after this
change as commit 8064952c6504 ("driver core: shut down devices
asynchronously") in -next. An easy test case due to the size of the
configuration:

  $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- mrproper virtconfig Image.gz

  $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20230707-182910/arm64-rootfs.cpio.zst | zstd -d >rootfs.cpio

  $ timeout --foreground 3m \
    qemu-system-aarch64 \
      -display none \
      -nodefaults \
      -cpu max,pauth-impdef=true \
      -machine virt,gic-version=max,virtualization=true \
      -append 'console=ttyAMA0 earlycon' \
      -kernel arch/arm64/boot/Image.gz \
      -initrd rootfs.cpio \
      -m 512m \
      -serial mon:stdio
  [    0.000000] Linux version 6.11.0-rc4-00022-g8064952c6504 (nathan at thelio-3990X) (aarch64-linux-gcc (GCC) 14.2.0, GNU ld (GNU Binutils) 2.42) #1 SMP PREEMPT Thu Sep  5 15:02:42 MST 2024
  ...
  The system is going down NOW!
  Sent SIGTERM to all processes
  Sent SIGKILL to all processes
  Requesting system poweroff
  qemu-system-aarch64: terminating on signal 15 from pid 2753792 (timeout)

At the parent commit, there are the following two prints after
"Requesting system poweroff" then the machine properly shuts down:

  [    3.411387] kvm: exiting hardware virtualization
  [    3.411741] reboot: Power down

If there is any other information I can provide or patches that I can
test, I am more than happy to do so.

Cheers,
Nathan