diff options
| author | Longpeng <longpeng2@huawei.com> | 2020-03-16 16:37:32 +0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-03-16 23:02:26 +0100 |
| commit | f962cac4c24157aeceff59cbf9dac8b5e30c55da (patch) | |
| tree | 4516763c219a4aebeb6f5e1fe9a93ce44dab8c1d /.gitpublish | |
| parent | 5073b5d3ea303d37f4a8e2ea451d7a2eb1817448 (diff) | |
cpus: avoid pause_all_vcpus getting stuck due to race
We found an issue when repeat reboot in guest during migration, it cause the
migration thread never be waken up again.
<main loop> |<migration_thread>
|
LOCK BQL |
... |
main_loop_should_exit |
pause_all_vcpus |
1. set all cpus ->stop=true |
and then kick |
2. return if all cpus is paused |
(by '->stopped == true'), else|
3. qemu_cond_wait [BQL UNLOCK] |
|LOCK BQL
|...
|do_vm_stop
| pause_all_vcpus
| (A)set all cpus ->stop=true
| and then kick
| (B)return if all cpus is paused
| (by '->stopped == true'), else
| (C)qemu_cond_wait [BQL UNLOCK]
4. be waken up and LOCK BQL | (D)be waken up BUT wait for BQL
5. goto 2. |
(BQL is still LOCKed) |
resume_all_vcpus |
1. set all cpus ->stop=false |
and ->stopped=false |
... |
BQL UNLOCK | (E)LOCK BQL
| (F)goto B. [but stopped is false now!]
|Finally, sleep at step 3 forever.
resume_all_vcpus should notice this race, so we need to move the change
of runstate before pause_all_vcpus in do_vm_stop() and ignore the resume
request if runstate is not running.
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Longpeng <longpeng2@huawei.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200316083732.2010-1-longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to '.gitpublish')
0 files changed, 0 insertions, 0 deletions