cgroup1_release_agent is a function that runs within a private ve workqueue. When exectured, it runs an executable in a userspace by a call to call_usermodehelper_ve. There is conflict that when ve is getting shutdown and some of last cgroups get's deleted at the same time, the workqueue might still be running, but ve_stop_ns has already been called. ve_stop_ns will stop usermode helper threads, needed for call_usermodehelper_ve. Because of that a call to call_usermodehelper_ve will never return, causing a hang. To defeat that hang VZ7 code of call_usermodehelper_ve included the check that ve is still running before running the userspace executable. It also checked for ve->init_task->flags & PF_EXITING condition. But in VZ8 the whole usermodehelper infrastructure is much more different. Also VZ8 does not have ve->init_task in it's fields. That's why it seems more relevant right now to do ve->is_running check before the call to call_usermodehelper_ve.
Signed-off-by: Valeriy Vdovin <[email protected]> --- kernel/cgroup/cgroup-v1.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 993ac38b895f..cd1a0df6c528 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -934,9 +934,12 @@ void cgroup1_release_agent(struct work_struct *work) envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin"; envp[i] = NULL; - mutex_unlock(&cgroup_mutex); + down_write(&ve->op_sem); + if (!ve->is_running) + goto continue_with_mutex; + err = call_usermodehelper_ve(ve, argv[0], argv, envp, UMH_WAIT_EXEC); @@ -944,6 +947,7 @@ void cgroup1_release_agent(struct work_struct *work) pr_warn_ratelimited("cgroup1_release_agent " "%s %s failed: %d\n", agentbuf, pathbuf, err); +continue_with_mutex: up_write(&ve->op_sem); mutex_lock(&cgroup_mutex); continue_free: -- 2.27.0 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
