Re: [PATCH v2 1/3] cgroup: Iterate tasks that did not finish do_exit()

[Tejun Heo]

On Fri, Jan 24, 2020 at 12:40:15PM +0100, Michal Koutný wrote:
> PF_EXITING is set earlier than actual removal from css_set when a task
> is exitting. This can confuse cgroup.procs readers who see no PF_EXITING
> tasks, however, rmdir is checking against css_set membership so it can
> transitionally fail with EBUSY.
> 
> Fix this by listing tasks that weren't unlinked from css_set active
> lists.
> It may happen that other users of the task iterator (without
> CSS_TASK_ITER_PROCS) spot a PF_EXITING task before cgroup_exit(). This
> is equal to the state before commit c03cd7738a83 ("cgroup: Include dying
> leaders with live threads in PROCS iterations") but it may be reviewed
> later.
> 
> Reported-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Fixes: c03cd7738a83 ("cgroup: Include dying leaders with live threads in PROCS iterations")
> Signed-off-by: Michal Koutný <mkoutny@xxxxxxxx>

Applied to cgroup/for-5.6-fixes.

Thanks.

-- 
tejun