On Wed, Aug 07, 2024 at 05:55:08PM GMT, yaozhenguo wrote:
When hotplug and hotunplug vhost-user-net device quickly.
I'd replace the . with ,
qemu will crash. BT is as below:
0 __pthread_kill_implementation () at /usr/lib64/libc.so.6
1 raise () at /usr/lib64/libc.so.6
2 abort () at /usr/lib64/libc.so.6
3 try_dequeue () at ../util/rcu.c:235
4 call_rcu_thread (opaque=opaque@entry=0x0) at ../util/rcu.c:288
5 qemu_thread_start (args=0x55b10d9ceaa0) at ../util/qemu-thread-posix.c:541
6 start_thread () at /usr/lib64/libc.so.6
7 clone3 () at /usr/lib64/libc.so.6
1. device_del qmp process
virtio_set_status
vhost_dev_stop
vhost_user_get_vring_base
vhost_user_host_notifier_remove
vhost_user_slave_handle_vring_host_notifier maybe called asynchronous after
^
Now it's called vhost_user_backend_handle_vring_host_notifier, I'd
suggest to use the new name.
vhost_user_host_notifier_remove. vhost_user_host_notifier_remove will
not
all call_rcu because of notifier->addr is NULL at this time.
s/all/call ?
2. netdev_del qmp process
vhost_user_cleanup
vhost_user_host_notifier_remove
g_free_rcu
vhost_user_host_notifier_remove and g_free_rcu will sumbit same rcu_head
s/sumbit/submit
to rcu node list. rcu_call_count add twice but only one node is added.
rcu thread will abort when calling try_dequeue with node list is empty.
What's not clear to me is how 1 and 2 are related, could you explain
that?
Fix this by moving g_free(n) to vhost_user_host_notifier_free.
`
Fixes: 503e355465 ("virtio/vhost-user: dynamically assign
VhostUserHostNotifiers")
Signed-off-by: yaozhenguo <yaozhen...@jd.com>
---
hw/virtio/vhost-user.c | 23 +++++++++++------------
include/hw/virtio/vhost-user.h | 1 +
2 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 00561daa06..7ab37c0da2 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1188,6 +1188,12 @@ static void
vhost_user_host_notifier_free(VhostUserHostNotifier *n)
assert(n && n->unmap_addr);
munmap(n->unmap_addr, qemu_real_host_page_size());
n->unmap_addr = NULL;
+ if (n->need_free) {
+ memory_region_transaction_begin();
+ object_unparent(OBJECT(&n->mr));
+ memory_region_transaction_commit();
+ g_free(n);
+ }
}
/*
@@ -1195,7 +1201,7 @@ static void
vhost_user_host_notifier_free(VhostUserHostNotifier *n)
* under rcu.
*/
static void vhost_user_host_notifier_remove(VhostUserHostNotifier *n,
- VirtIODevice *vdev)
+ VirtIODevice *vdev, bool free)
{
if (n->addr) {
if (vdev) {
@@ -1204,6 +1210,7 @@ static void
vhost_user_host_notifier_remove(VhostUserHostNotifier *n,
assert(!n->unmap_addr);
n->unmap_addr = n->addr;
n->addr = NULL;
+ n->need_free = free;
call_rcu(n, vhost_user_host_notifier_free, rcu);
}
}
@@ -1280,7 +1287,7 @@ static int vhost_user_get_vring_base(struct vhost_dev
*dev,
VhostUserHostNotifier *n = fetch_notifier(u->user, ring->index);
if (n) {
- vhost_user_host_notifier_remove(n, dev->vdev);
+ vhost_user_host_notifier_remove(n, dev->vdev, false);
}
ret = vhost_user_write(dev, &msg, NULL, 0);
@@ -1562,7 +1569,7 @@ static int
vhost_user_backend_handle_vring_host_notifier(struct vhost_dev *dev,
* new mapped address.
*/
n = fetch_or_create_notifier(user, queue_idx);
- vhost_user_host_notifier_remove(n, vdev);
+ vhost_user_host_notifier_remove(n, vdev, false);
if (area->u64 & VHOST_USER_VRING_NOFD_MASK) {
return 0;
@@ -2737,13 +2744,7 @@ static void vhost_user_state_destroy(gpointer data)
{
VhostUserHostNotifier *n = (VhostUserHostNotifier *) data;
if (n) {
- vhost_user_host_notifier_remove(n, NULL);
- object_unparent(OBJECT(&n->mr));
- /*
- * We can't free until vhost_user_host_notifier_remove has
- * done it's thing so schedule the free with RCU.
- */
- g_free_rcu(n, rcu);
+ vhost_user_host_notifier_remove(n, NULL, true);
I'm not sure I understand the problem well, but could it be that now we
don't see the problem anymore, but we have a memory leak?
Here for example could it be the case that `n->addr` is NULL and
therefore `vhost_user_host_notifier_free` with `n->need_free = true`
will never be submitted?
}
}
@@ -2765,9 +2766,7 @@ void vhost_user_cleanup(VhostUserState *user)
if (!user->chr) {
return;
}
- memory_region_transaction_begin();
user->notifiers = (GPtrArray *) g_ptr_array_free(user->notifiers,
true);
- memory_region_transaction_commit();
This is no longer necessary, because the `user->notifiers` free function
no longer calls `object_unparent(OBJECT(&n->mr))`, right?
Maybe it's worth mentioning in the commit description.
user->chr = NULL;
}
diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index 324cd8663a..a171f29e0b 100644
--- a/include/hw/virtio/vhost-user.h
+++ b/include/hw/virtio/vhost-user.h
@@ -54,6 +54,7 @@ typedef struct VhostUserHostNotifier {
void *addr;
void *unmap_addr;
int idx;
+ bool need_free;
} VhostUserHostNotifier;
/**
--
2.43.0
