Re: [PATCH] cgroup/cpuset: fix circular locking dependency
From: Tejun Heo <tj@kernel.org>
Date: 2017-12-15 13:22:38
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Hello, Prateek. On Fri, Dec 15, 2017 at 02:24:55PM +0530, Prateek Sood wrote:
quoted hunk ↗ jump to hunk
Following are two ways to improve cgroup_transfer_tasks(). In both cases task in PF_EXITING state would be left in source cgroup. It would be removed from cgroup_exit() in exit path.diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 024085d..e2bdcdb 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c@@ -123,7 +123,10 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from) */ do { css_task_iter_start(&from->self, 0, &it); - task = css_task_iter_next(&it); + do { + task = css_task_iter_next(&it); + } while (task && (task & PF_EXITING)) +
Yeah, this looks good to me. We can't just make a single pass as in the other one because we can race aginst fork. And PF_EXITING being left behind is what was happening previously too anyway. They can't be moved. Thanks. -- tejun