Betty reported hitting the following warning:
[ 8.709131][ T221] WARNING: CPU: 2 PID: 221 at kernel/workqueue.c:4182
...
[ 8.713282][ T221] Call trace:
[ 8.713365][ T221] __flush_work+0x8d0/0x914
[ 8.713468][ T221] __cancel_work_sync+0xac/0xfc
[ 8.713570][ T221] cancel_work_sync+0x24/0x34
[ 8.713667][ T221] virtsnd_remove+0xa8/0xf8 [virtio_snd ab15f34d0dd772f6d11327e08a81d46dc9c36276]
[ 8.713868][ T221] virtsnd_probe+0x48c/0x664 [virtio_snd ab15f34d0dd772f6d11327e08a81d46dc9c36276]
[ 8.714035][ T221] virtio_dev_probe+0x28c/0x390
[ 8.714139][ T221] really_probe+0x1bc/0x4c8
...
It seems we're hitting the error path in virtsnd_probe(), which
triggers a virtsnd_remove() which iterates over the substreams
calling cancel_work_sync() on the elapsed_period work_struct.
Looking at the code, from earlier in:
virtsnd_probe()->virtsnd_build_devs()->virtsnd_pcm_parse_cfg()
We set snd->nsubstreams, allocate the snd->substreams, and if
we then hit an error on the info allocation or something in
virtsnd_ctl_query_info() fails, we will exit without having
initialized the elapsed_period work_struct.
When that error path unwinds we then call virtsnd_remove()
which as long as the substreams array is allocated, will iterate
through calling cancel_work_sync() on the uninitialized work
struct hitting this warning.
The simplest fix seems to just check the work_struct->func ptr
is valid before calling cancel_work_sync(), but I wanted to share
in case folks had ideas for a better solution.
I have not yet managed to reproduce the issue myself, so this
patch has had limited testing.
Feedback or thoughts would be appreciated!
Cc: Anton Yakovlev <anton.yakovlev@xxxxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jaroslav Kysela <perex@xxxxxxxx>
Cc: Takashi Iwai <tiwai@xxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxx
Cc: linux-sound@xxxxxxxxxxxxxxx
Cc: kernel-team@xxxxxxxxxxx
Reported-by: Betty Zhou <bettyzhou@xxxxxxxxxx>
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
---
sound/virtio/virtio_card.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/sound/virtio/virtio_card.c b/sound/virtio/virtio_card.c
index 965209e1d872..87dc49c9390a 100644
--- a/sound/virtio/virtio_card.c
+++ b/sound/virtio/virtio_card.c
@@ -365,7 +365,9 @@ static void virtsnd_remove(struct virtio_device *vdev)
for (i = 0; snd->substreams && i < snd->nsubstreams; ++i) {
struct virtio_pcm_substream *vss = &snd->substreams[i];
- cancel_work_sync(&vss->elapsed_period);
+ /* check we initialized the work struct before cancelling*/
+ if (vss->elapsed_period.func)
+ cancel_work_sync(&vss->elapsed_period);
virtsnd_pcm_msg_free(vss);
}
--
2.48.0.rc2.279.g1de40edade-goog
