The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear
at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.5
------>
commit b731c902e757211385077720bb021e0e56bf1d81
Author: Valeriy Vdovin <[email protected]>
Date: Wed Mar 3 20:21:16 2021 +0300
cgroup/ve: Do not run release_agent on non-running ve
cgroup1_release_agent is a function that runs within a private
ve workqueue. When executed, 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 gets 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]>
Reviewed-by: Kirill Tkhai <[email protected]>
=====================
Patchset description:
ve/cgroup: Port release_agent virtualization from vz7
This patchset ports virtualization of cgroup release_agent
virtualization from vz7.
Major challanges of porting are differences between vz7 and vz8 cgroup
implementations:
- transition of cgroups to kernfs
- slightly changed locking scheme, which relies on css_set_lock in
places, previously relied on cgroup_mutex.
There is a small number of patches that have been ported without
modifications, but most of the patches had suffered a lot of
modification due to the factors described above.
v1:
- original patchset
v2:
- removed port of CGRP_REMOVED due to the use of CSS_ONLINE in VZ8 for
same reason
- changed ve_set(get)_release_agent_path signature for more optimal
- added ve->is_running check before calling userspace executable
v3:
- use goto after check for ve->is_running in last patch
---
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:
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