21.05.2026 05:19, Ryosuke Yasuoka пишет: > virtio_gpu_queue_ctrl_sgs() and virtio_gpu_queue_cursor() use > wait_event() without any abort condition when waiting for virtqueue > space. If the host device stops processing commands, these waits block > indefinitely inside a drm_dev_enter/exit() critical section. Since > drm_dev_unplug(), which is called in device removal and system shutdown > call path, blocks on synchronize_srcu() until all critical sections > complete, device removal and system shutdown also hang. > > Add a vqs_released flag to virtio_gpu_device and include it in the > wait_event() condition. Set the flag and wake up both queues in a new > virtio_gpu_release_vqs() helper, called before drm_dev_unplug() in both > virtio_gpu_remove() and virtio_gpu_shutdown(). When the flag is set, the > wait returns immediately and the command is aborted, following the same > cleanup path as drm_dev_enter() failure. > > Reported-by: > syzbot+d6dd6f86d3aaf7eebe7406e45c1c6e549453f...@syzkaller.appspotmail.com > Closes: > https://syzkaller.appspot.com/bug?id=d6dd6f86d3aaf7eebe7406e45c1c6e549453f224 > Reported-by: > syzbot+908bd910da5dd79b88de4cf7baf376cc873a9...@syzkaller.appspotmail.com > Closes: > https://syzkaller.appspot.com/bug?id=908bd910da5dd79b88de4cf7baf376cc873a922e > Signed-off-by: Ryosuke Yasuoka <[email protected]> > --- > Changes in v2: > - Update the commit message. > - Replace wait_event_timeout() with wait_event() using a compound > condition that includes a new vqs_released flag. > - Add virtio_gpu_release_vqs() helper to set the flag and wake up > both queues, called before drm_dev_unplug() in remove and shutdown > paths. > - Remove the hardcoded 5-second timeout. Recovery is now driven by > the driver flag instead of an arbitrary timeout value. > --- > drivers/gpu/drm/virtio/virtgpu_drv.c | 15 +++++++++++++++ > drivers/gpu/drm/virtio/virtgpu_drv.h | 1 + > drivers/gpu/drm/virtio/virtgpu_vq.c | 23 +++++++++++++++++++++-- > 3 files changed, 37 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c > b/drivers/gpu/drm/virtio/virtgpu_drv.c > index a5ce96fb8a1d..e4fe5e0780f9 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_drv.c > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c > @@ -119,10 +119,24 @@ static int virtio_gpu_probe(struct virtio_device *vdev) > return ret; > } > > +/* > + * Release pending virtqueue waits so the drm_dev_enter/exit() critical > + * sections complete before drm_dev_unplug() blocks on synchronize_srcu(). > + */ > +static void virtio_gpu_release_vqs(struct drm_device *dev) > +{ > + struct virtio_gpu_device *vgdev = dev->dev_private; > + > + vgdev->vqs_released = true; > + wake_up_all(&vgdev->ctrlq.ack_queue); > + wake_up_all(&vgdev->cursorq.ack_queue); > +} > + > static void virtio_gpu_remove(struct virtio_device *vdev) > { > struct drm_device *dev = vdev->priv; > > + virtio_gpu_release_vqs(dev); > drm_dev_unplug(dev); > drm_atomic_helper_shutdown(dev); > virtio_gpu_deinit(dev); > @@ -133,6 +147,7 @@ static void virtio_gpu_shutdown(struct virtio_device > *vdev) > { > struct drm_device *dev = vdev->priv; > > + virtio_gpu_release_vqs(dev); > /* stop talking to the device */ > drm_dev_unplug(dev); > } > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h > b/drivers/gpu/drm/virtio/virtgpu_drv.h > index f17660a71a3e..0bd69a40857e 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_drv.h > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h > @@ -235,6 +235,7 @@ struct virtio_gpu_device { > > struct virtio_gpu_queue ctrlq; > struct virtio_gpu_queue cursorq; > + bool vqs_released; > struct kmem_cache *vbufs; > > atomic_t pending_commands; > diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c > b/drivers/gpu/drm/virtio/virtgpu_vq.c > index 67865810a2e7..8057a9b7356d 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_vq.c > +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c > @@ -396,7 +396,19 @@ static int virtio_gpu_queue_ctrl_sgs(struct > virtio_gpu_device *vgdev, > if (vq->num_free < elemcnt) { > spin_unlock(&vgdev->ctrlq.qlock); > virtio_gpu_notify(vgdev); > - wait_event(vgdev->ctrlq.ack_queue, vq->num_free >= elemcnt); > + wait_event(vgdev->ctrlq.ack_queue, > + vq->num_free >= elemcnt || vgdev->vqs_released); > + /* > + * Set by virtio_gpu_release_vqs() to unblock > + * synchronize_srcu() wait in drm_dev_unplug(). > + */ > + if (vgdev->vqs_released) { > + if (fence && vbuf->objs) > + virtio_gpu_array_unlock_resv(vbuf->objs); > + free_vbuf(vgdev, vbuf); > + drm_dev_exit(idx); > + return -ENODEV; > + } > goto again; > } > > @@ -566,7 +578,14 @@ static void virtio_gpu_queue_cursor(struct > virtio_gpu_device *vgdev, > ret = virtqueue_add_sgs(vq, sgs, outcnt, 0, vbuf, GFP_ATOMIC); > if (ret == -ENOSPC) { > spin_unlock(&vgdev->cursorq.qlock); > - wait_event(vgdev->cursorq.ack_queue, vq->num_free >= outcnt); > + wait_event(vgdev->cursorq.ack_queue, > + vq->num_free >= outcnt || vgdev->vqs_released); > + /* See comment in virtio_gpu_queue_ctrl_sgs(). */ > + if (vgdev->vqs_released) { > + free_vbuf(vgdev, vbuf); > + drm_dev_exit(idx); > + return; > + } > spin_lock(&vgdev->cursorq.qlock); > goto retry; > } else {
What about other wait_event in the driver? Why only these? -- Best regards, Dmitry
