linux-kernel - Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

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Message-ID: <20190314231641.5a37932b@oasis.local.home>
Date:   Thu, 14 Mar 2019 23:16:41 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sultan Alsawaf <sultan@...neltoast.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        Tim Murray <timmurray@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Christian Brauner <christian@...uner.io>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        linux-mm <linux-mm@...ck.org>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for
 Android

On Thu, 14 Mar 2019 13:49:11 -0700
Sultan Alsawaf <sultan@...neltoast.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