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From: | Stefan Hajnoczi |
Subject: | Re: [PATCH] virtio-scsi: avoid dangling host notifier in ->ioeventfd_stop() |
Date: | Sun, 11 Jun 2023 15:51:17 -0400 |
virtio_scsi_dataplane_stop() calls blk_drain_all(), which invokes
->drained_begin()/->drained_end() after we've already detached the host
notifier. virtio_scsi_drained_end() currently attaches the host notifier
again and leaves it dangling after dataplane has stopped.
This results in the following assertion failure because
virtio_scsi_defer_to_dataplane() is called from the IOThread instead of
the main loop thread:
qemu-system-x86_64: ../softmmu/memory.c:1111: memory_region_transaction_commit: Assertion `qemu_mutex_iothread_locked()' failed.
Reported-by: Jean-Louis Dupond <jean-louis@dupond.be>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/scsi/virtio-scsi.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 9c8ef0aaa6..45b95ea070 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -1125,7 +1125,16 @@ static void virtio_scsi_drained_begin(SCSIBus *bus)
uint32_t total_queues = VIRTIO_SCSI_VQ_NUM_FIXED +
s->parent_obj.conf.num_queues;
- if (!s->dataplane_started) {
+ /*
+ * Drain is called when stopping dataplane but the host notifier has
+ * already been detached. Detaching multiple times is a no-op if nothing
+ * else is using the monitoring same file descriptor, but avoid it just in
+ * case.
+ *
+ * Also, don't detach if dataplane has not even been started yet because
+ * the host notifier isn't attached.
+ */
+ if (s->dataplane_stopping || !s->dataplane_started) {
return;
}
@@ -1143,7 +1152,14 @@ static void virtio_scsi_drained_end(SCSIBus *bus)
uint32_t total_queues = VIRTIO_SCSI_VQ_NUM_FIXED +
s->parent_obj.conf.num_queues;
- if (!s->dataplane_started) {
+ /*
+ * Drain is called when stopping dataplane. Keep the host notifier detached
+ * so it's not left dangling after dataplane is stopped.
+ *
+ * Also, don't attach if dataplane has not even been started yet. We're not
+ * ready.
+ */
+ if (s->dataplane_stopping || !s->dataplane_started) {
return;
}
--
2.40.1
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