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Date:   Thu, 25 May 2023 13:55:13 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Mike Christie <michael.christie@oracle.com>, linux@leemhuis.info,
        nicolas.dichtel@6wind.com, axboe@kernel.dk,
        torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, mst@redhat.com,
        sgarzare@redhat.com, jasowang@redhat.com, stefanha@redhat.com,
        brauner@kernel.org
Subject: Re: [PATCH 3/3] fork, vhost: Use CLONE_THREAD to fix freezer/ps
 regression
Message-ID: <20230525115512.GA9229@redhat.com>
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On 05/24, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@redhat.com> writes:
>
> > Yes, but probably SIGABRT/exit doesn't really differ from SIGKILL wrt
> > vhost_worker().
>
> Actually I think it reveals that exiting with SIGABRT will cause
> a deadlock.
>
> coredump_wait will wait for all of the threads to reach
> coredump_task_exit.  Meanwhile vhost_worker is waiting for
> all of the other threads to reach exit_files to close their
> file descriptors.

Indeed, I didn't think about this.


So why do we actually need CLONE_THREAD ? Can't vhost_worker() be a kernel thread?

kthread_create() won't be convenient, but how about kernel_thread() ? it inherits
mm/cgroups/rlimits/etc, kthread_stop() should work just fine.

Oleg.