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authorRoman Gushchin <guro@fb.com>2019-04-26 10:59:44 -0700
committerTejun Heo <tj@kernel.org>2019-05-06 08:39:06 -0700
commitcb2c4cd87874a7975b7b8615866b3a87bae10aab (patch)
tree306f73b6b4208a222e4e8e3902d5de62668eb5cb /kernel/signal.c
parent533307dc20a9e84a0687d4ca24aeb669516c0243 (diff)
downloadlinux-cb2c4cd87874a7975b7b8615866b3a87bae10aab.tar.bz2
cgroup: prevent spurious transition into non-frozen state
If freezing of a cgroup races with waking of a task from the frozen state (like waiting in vfork() or in do_signal_stop()), a spurious transition of the cgroup state can happen. The task enters cgroup_leave_frozen(true), the cgroup->nr_frozen_tasks counter decrements, and the cgroup is switched to the unfrozen state. To prevent it, let's reserve cgroup_leave_frozen(true) for terminating processes and use cgroup_leave_frozen(false) otherwise. To avoid busy-looping in the signal handling loop waiting for JOBCTL_TRAP_FREEZE set from the cgroup freezing path, let's do it explicitly in cgroup_leave_frozen(), if the task is going to stay frozen. Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/signal.c')
-rw-r--r--kernel/signal.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 095e0fc57b25..16b72f4f14df 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2514,7 +2514,7 @@ relock:
*/
if (unlikely(cgroup_task_frozen(current))) {
spin_unlock_irq(&sighand->siglock);
- cgroup_leave_frozen(true);
+ cgroup_leave_frozen(false);
goto relock;
}