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963b027645
During the hot-unplugging of vhost-user-net type network cards,
the vhost_user_cleanup function may add the same rcu node to
the rcu linked list. The function call in this case is as follows:
vhost_user_cleanup
->vhost_user_host_notifier_remove
->call_rcu(n, vhost_user_host_notifier_free, rcu);
->g_free_rcu(n, rcu);
When this happens, QEMU will abort in try_dequeue:
if (head == &dummy && qatomic_mb_read(&tail) == &dummy.next) {
abort();
}
backtrace is as follows:
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 (0) at ../util/rcu.c:288
5 qemu_thread_start (0) at ../util/qemu-thread-posix.c:541
6 start_thread () at /usr/lib64/libc.so.6
7 clone3 () at /usr/lib64/libc.so.6
The reason for the abort is that adding two identical nodes to
the rcu linked list will cause the rcu linked list to become a ring,
but when the dummy node is added after the two identical nodes,
the ring is opened. But only one node is added to list with
rcu_call_count added twice. This will cause rcu try_dequeue abort.
This happens when n->addr != 0. In some scenarios, this does happen.
For example, this situation will occur when using a 32-queue DPU
vhost-user-net type network card for hot-unplug testing, because
VhostUserHostNotifier->addr will be cleared during the processing of
VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG. However,it is asynchronous,
so we cannot guarantee that VhostUserHostNotifier->addr is zero in
vhost_user_cleanup. Therefore, it is necessary to merge g_free_rcu
and vhost_user_host_notifier_free into one rcu node.
Fixes:
|
||
|---|---|---|
| .. | ||
| authz | ||
| block | ||
| chardev | ||
| crypto | ||
| disas | ||
| exec | ||
| fpu | ||
| gdbstub | ||
| hw | ||
| io | ||
| libdecnumber | ||
| migration | ||
| monitor | ||
| net | ||
| qapi | ||
| qemu | ||
| qom | ||
| scsi | ||
| semihosting | ||
| standard-headers | ||
| sysemu | ||
| tcg | ||
| ui | ||
| user | ||
| elf.h | ||
| glib-compat.h | ||
| qemu-io.h | ||
| qemu-main.h | ||