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Date:   Thu, 14 Mar 2019 23:16:41 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Sultan Alsawaf <sultan@kerneltoast.com>
Cc:     Joel Fernandes <joel@joelfernandes.org>,
        Tim Murray <timmurray@google.com>,
        Michal Hocko <mhocko@kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Arve =?UTF-8?B?SGrDuG5uZXbDpWc=?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>,
        Martijn Coenen <maco@android.com>,
        Christian Brauner <christian@brauner.io>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
        linux-mm <linux-mm@kvack.org>,
        kernel-team <kernel-team@android.com>
Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for
 Android
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On Thu, 14 Mar 2019 13:49:11 -0700
Sultan Alsawaf <sultan@kerneltoast.com> wrote:

> Perhaps I'm missing something, but if you want to know when a process has died
> after sending a SIGKILL to it, then why not just make the SIGKILL optionally
> block until the process has died completely? It'd be rather trivial to just
> store a pointer to an onstack completion inside the victim process' task_struct,
> and then complete it in free_task().

How would you implement such a method in userspace? kill() doesn't take
any parameters but the pid of the process you want to send a signal to,
and the signal to send. This would require a new system call, and be
quite a bit of work. If you can solve this with an ebpf program, I
strongly suggest you do that instead.

-- Steve