linux-kernel - Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+55aFzk0Lh1kQRRvOQKrjMfkcuQem0aV5D9cCUmmtfw7ZamkQ@mail.gmail.com>
Date:   Wed, 17 Jan 2018 13:58:10 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     David Miller <davem@...emloft.net>, Mike Galbraith <efault@....de>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Dmitry Safonov <dima@...sta.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <alexander.levin@...izon.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Radu Rendec <rrendec@...sta.com>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context

On Wed, Jan 17, 2018 at 1:54 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> raise_softirq() -> raise_softirq_irqoff()
>
>         set_softirq_bit();
>
>         if (!in_interrupt())
>                 wake_softirqd();
>
> So if the caller is not in hard or soft interrupt context, which includes
> bottom half disabled regions softirqd is woken.

That does seem unnecessarily expensive, and maybe we could just do it
with thread flag (TIF_NOTIFY_RESUME or whatever).

In fact, that was what I *thought* we did. Maybe I just remember some
historical behavior.

Since networking seems to largely prefer softirqd anyway, maybe that
wake_softirqd() is the right thing to do anyway.

             Linus