Re: [PATCH 1/1] Revert "kmod: handle UMH_WAIT_PROC from system unbound workqueue"

[Frederic Weisbecker]

On Wed, Oct 14, 2015 at 08:52:09PM +0200, Oleg Nesterov wrote:
> This reverts commit bb304a5c6fc63d8506cd9741a3a5f35b73605625.
> 
> Because this patch leads to kthread zombies.
> 
> call_usermodehelper_exec_sync() does fork() + wait() with "unignored"
> SIGCHLD. What we have missed is that this worker thread can have other
> children previously forked by call_usermodehelper_exec_work() without
> UMH_WAIT_PROC. If such a child exits in between it becomes a zombie
> and nobody can reap it (unless/until this worker thread exits too).

I missed that indeed. But then when we create the async thread with
UMH_NO_WAIT, who reaps it? It's created by the workqueue which never
exits.

And on others cases, who buries the sync thread?
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