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virtio_ccw: always take irq_lock in the classic interrupt handler

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virtio_ccw_int_handler() takes vcdev->irq_lock around its
vring_interrupt() calls only when VIRTIO_HARDEN_NOTIFICATION is enabled.

The virtio shutdown path calls synchronize_cbs() even when notification
hardening is disabled. virtio_reset_device() now does so after the
transport reset too.

For classic interrupts, synchronize_cbs() takes vcdev->irq_lock for
writing, but the interrupt handler does not take the matching read
lock in that configuration. synchronize_cbs() can return while a
callback is still running.

Take the read lock unconditionally so the write side can synchronize
with the callbacks.

Fixes: 8bd2fa086a ("virtio: break and reset virtio devices on device_shutdown()")
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260908053817.26065-3-kmehltretter@gmail.com>
This commit is contained in:
Karl Mehltretter 2026-09-08 07:38:13 +02:00 committed by Michael S. Tsirkin
parent 6e484b870b
commit 48a355cf5b
1 changed files with 0 additions and 4 deletions
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4
drivers/s390/virtio/virtio_ccw.c
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@ -1204,13 +1204,11 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
vcdev->err = -EIO;
}
virtio_ccw_check_activity(vcdev, activity);
#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
/*
* Paired with virtio_ccw_synchronize_cbs() and interrupts are
* disabled here.
*/
read_lock(&vcdev->irq_lock);
#endif
for_each_set_bit(i, indicators(vcdev),
sizeof(*indicators(vcdev)) * BITS_PER_BYTE) {
/* The bit clear must happen before the vring kick. */
@ -1219,9 +1217,7 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
vq = virtio_ccw_vq_by_ind(vcdev, i);
vring_interrupt(0, vq);
}
#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
read_unlock(&vcdev->irq_lock);
#endif
if (test_bit(0, indicators2(vcdev))) {
virtio_config_changed(&vcdev->vdev);
clear_bit(0, indicators2(vcdev));