From: Andi Kleen <andi@firstfloor.org>
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
peterz@infradead.org, akpm@linux-foundation.org,
andi.kleen@intel.com, rob@landley.net, viro@zeniv.linux.org.uk,
oleg@redhat.com, gnomes@lxorguk.ukuu.org.uk, riel@redhat.com,
snorcht@gmail.com, dhowells@redhat.com, luto@amacapital.net,
daeseok.youn@gmail.com, ebiederm@xmission.com,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v2] Pre-emption control for userspace
Date: Tue, 25 Mar 2014 11:20:04 -0700 [thread overview]
Message-ID: <871txqp2cr.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <1395767870-28053-1-git-send-email-khalid.aziz@oracle.com> (Khalid Aziz's message of "Tue, 25 Mar 2014 11:17:50 -0600")
Khalid Aziz <khalid.aziz@oracle.com> writes:
First it would be nice to have some standard reference lock library that
uses this. What would it take to support this in glibc?
> +==================================
> +Using the preemption delay feature
> +==================================
> +
> +This feature is enabled in the kernel by setting
> +CONFIG_SCHED_PREEMPT_DELAY in kernel configuration. Once this feature is
> +enabled, the userspace process communicates with the kernel using a
> +4-byte memory location in its address space. It first gives the kernel
> +address for this memory location by writing its address to
> +/proc/<tgid>/task/<tid>/sched_preempt_delay. This memory location is
> +interpreted as a sequence of 4 bytes:
> +
> + byte[0] = flag to request preemption delay
> + byte[1] = flag from kernel indicating preemption delay was granted
> + byte[2] = reserved for future use
> + byte[3] = reserved for future use
Should reserve more bytes (64, 128?) and rename the proc flag
to a more generic name. I could well assume other things
using such a mechanism in the future. Also please add a flag
word with feature bits (similar to the perf mmap page)
How about alignment? x86 will not care, but other architectures
may.
> #endif
> +#ifdef CONFIG_SCHED_PREEMPT_DELAY
> + REG("sched_preempt_delay", S_IRUGO|S_IWUSR,
> proc_tid_preempt_delay_ops),
This shouldn't be readable by group/other, as it exposes the address space,
so could help exploits.
> @@ -2061,6 +2069,13 @@ extern u64 scheduler_tick_max_deferment(void);
> static inline bool sched_can_stop_tick(void) { return false; }
> #endif
>
> +#if defined(CONFIG_SCHED_PREEMPT_DELAY) && defined(CONFIG_PROC_FS)
> +extern void sched_preempt_delay_show(struct seq_file *m,
> + struct task_struct *task);
> +extern void sched_preempt_delay_set(struct task_struct *task,
> + unsigned char *val);
> +#endif
Prototypes don't need to be ifdefed.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2014-03-25 18:28 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-03 18:07 [RFC] [PATCH] Pre-emption control for userspace Khalid Aziz
2014-03-03 21:51 ` Davidlohr Bueso
2014-03-03 23:29 ` Khalid Aziz
2014-03-04 13:56 ` Oleg Nesterov
2014-03-04 17:44 ` Khalid Aziz
2014-03-04 18:38 ` Al Viro
2014-03-04 19:01 ` Khalid Aziz
2014-03-04 19:03 ` Oleg Nesterov
2014-03-04 20:14 ` Khalid Aziz
2014-03-05 14:38 ` Oleg Nesterov
2014-03-05 16:12 ` Oleg Nesterov
2014-03-05 17:10 ` Khalid Aziz
2014-03-04 21:12 ` H. Peter Anvin
2014-03-04 21:39 ` Khalid Aziz
2014-03-04 22:23 ` One Thousand Gnomes
2014-03-04 22:44 ` Khalid Aziz
2014-03-05 0:39 ` Thomas Gleixner
2014-03-05 0:51 ` Andi Kleen
2014-03-05 11:10 ` Peter Zijlstra
2014-03-05 17:29 ` Khalid Aziz
2014-03-05 19:58 ` Khalid Aziz
2014-03-06 9:57 ` Peter Zijlstra
2014-03-06 16:08 ` Khalid Aziz
2014-03-06 11:14 ` Thomas Gleixner
2014-03-06 16:32 ` Khalid Aziz
2014-03-05 14:54 ` Oleg Nesterov
2014-03-05 15:56 ` Andi Kleen
2014-03-05 16:36 ` Oleg Nesterov
2014-03-05 17:22 ` Khalid Aziz
2014-03-05 23:13 ` David Lang
2014-03-05 23:48 ` Khalid Aziz
2014-03-05 23:56 ` H. Peter Anvin
2014-03-06 0:02 ` Khalid Aziz
2014-03-06 0:13 ` H. Peter Anvin
2014-03-05 23:59 ` David Lang
2014-03-06 0:17 ` Khalid Aziz
2014-03-06 0:36 ` David Lang
2014-03-06 1:22 ` Khalid Aziz
2014-03-06 14:23 ` David Lang
2014-03-06 12:13 ` Kevin Easton
2014-03-06 13:59 ` Peter Zijlstra
2014-03-06 22:41 ` Andi Kleen
2014-03-06 14:25 ` David Lang
2014-03-06 16:12 ` Khalid Aziz
2014-03-06 13:24 ` Rasmus Villemoes
2014-03-06 13:34 ` Peter Zijlstra
2014-03-06 13:45 ` Rasmus Villemoes
2014-03-06 14:02 ` Peter Zijlstra
2014-03-06 14:33 ` Thomas Gleixner
2014-03-06 14:34 ` H. Peter Anvin
2014-03-06 14:04 ` Thomas Gleixner
2014-03-25 17:17 ` [PATCH v2] " Khalid Aziz
2014-03-25 17:44 ` Andrew Morton
2014-03-25 17:56 ` Khalid Aziz
2014-03-25 18:14 ` Andrew Morton
2014-03-25 17:46 ` Oleg Nesterov
2014-03-25 17:59 ` Khalid Aziz
2014-03-25 18:20 ` Andi Kleen [this message]
2014-03-25 18:47 ` Khalid Aziz
2014-03-25 19:47 ` Andi Kleen
2014-03-25 18:59 ` Eric W. Biederman
2014-03-25 19:15 ` Khalid Aziz
2014-03-25 20:31 ` Eric W. Biederman
2014-03-25 21:37 ` Khalid Aziz
2014-03-26 6:03 ` Mike Galbraith
2014-03-25 23:01 ` [RFC] [PATCH] " Davidlohr Bueso
2014-03-25 23:29 ` Khalid Aziz
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