From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: John Stultz <john.stultz@linaro.org>,
lkml <linux-kernel@vger.kernel.org>,
Ruchi Kandoi <kandoiruchi@google.com>,
Arjan van de Ven <arjan@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Oren Laadan <orenl@cellrox.com>,
Rom Lemarchand <romlem@android.com>,
Android Kernel Team <kernel-team@android.com>
Subject: Re: [PATCH] prctl: Add PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread.
Date: Fri, 5 Feb 2016 12:50:08 -0800 [thread overview]
Message-ID: <20160205125008.15ccbdbe82afc3521a8ee381@linux-foundation.org> (raw)
In-Reply-To: <CAGXu5j+W0oOCu1RR9FpEwX8ztiNHnpGpO2PyS54oMG85Yf08GQ@mail.gmail.com>
On Fri, 5 Feb 2016 12:44:04 -0800 Kees Cook <keescook@chromium.org> wrote:
> On Fri, Feb 5, 2016 at 12:39 PM, John Stultz <john.stultz@linaro.org> wrote:
> > On Fri, Feb 5, 2016 at 12:32 PM, Andrew Morton
> > <akpm@linux-foundation.org> wrote:
> >> On Fri, 5 Feb 2016 12:23:13 -0800 John Stultz <john.stultz@linaro.org> wrote:
> >>> On Fri, Feb 5, 2016 at 12:13 PM, Andrew Morton
> >>> <akpm@linux-foundation.org> wrote:
> >>>>
> >>>> IOW, it would be more consistent to add sys_set_timer_slack()?
> >>>
> >>> I'm fine with moving this way.
> >>>
> >>> Ruchi/Rom: Any objections to that idea?
> >>>
> >>> Thomas/Arjan: Any other functionality we should consider including
> >>> when adding a syscall to tweak timer slack?
> >>
> >> A syscall is quite a bit more fuss - implement it on x86_64, provide a
> >> no-op default in sys_ni.c, add a test suite into
> >> tools/testing/selftests (mainly for arch maintainers), wait for the
> >> various arch maintainers to wire it up.
> >
> > Yea. It is. And I'm not excited to start over on this, but this
> > functionality has already run into trouble in the Android tree, as the
> > PR_SET_TIMERSLACK_PID value has hit multiple collisions over time. So
> > this functionality upstream would help resolve that pain.
> >
> >> Fortunately the build system now emits little messages which tell
> >> maintainers that there's a new syscall which needs looking at.
> >>
> >> And a manpage will be needed, but a prctl manpage patch would have been
> >> needed anyway.
> >
> > Yea.
>
> Could this be exposed as a writable /proc entry instead? Like the oom_* stuff?
/proc/<pid>/timer_slack_ns, guarded by ptrace_may_access(), documented
under Documentation/? Yup, that would work. It's there for all
architectures from day one and there is precedent. It's not as nice,
but /proc nasties will always be with us.
next prev parent reply other threads:[~2016-02-05 20:50 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-05 18:08 [PATCH] prctl: Add PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread John Stultz
2016-02-05 20:10 ` Kees Cook
2016-02-05 20:18 ` John Stultz
2016-02-05 20:13 ` Andrew Morton
2016-02-05 20:23 ` John Stultz
2016-02-05 20:32 ` Andrew Morton
2016-02-05 20:39 ` John Stultz
2016-02-05 20:44 ` Kees Cook
2016-02-05 20:50 ` Andrew Morton [this message]
2016-02-05 22:35 ` John Stultz
2016-02-06 0:51 ` John Stultz
2016-02-06 1:56 ` Andrew Morton
2016-02-06 2:41 ` John Stultz
2016-02-06 2:15 ` Arjan van de Ven
2016-02-06 2:50 ` John Stultz
2016-02-06 2:54 ` Arjan van de Ven
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