From: Mike Galbraith <efault@gmx.de>
To: lkml <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Subject: Re: [2.6.16-rc6 patch] smp fix for recalc_task_prio()
Date: Sat, 18 Mar 2006 05:41:40 +0100 [thread overview]
Message-ID: <1142656901.8262.13.camel@homer> (raw)
In-Reply-To: <1142656637.8262.9.camel@homer>
On Sat, 2006-03-18 at 05:37 +0100, Mike Galbraith wrote:
> Greetings,
>
> The patchlet below fixes an smp buglet where a task goes to sleep on one
> cpu and wakes up on another, causing recalc_task_prio() to be called
> with now < p->timestamp.
>
> If this isn't 2.6.16 material, and I can respin against mm.
Sigh. Forgot sob line.
-Mike
Signed-off-by: Mike Galbraith <efault@gmx.de>
--- linux-2.6.16-rc6/kernel/sched.c.org 2006-03-17 14:48:35.000000000 +0100
+++ linux-2.6.16-rc6/kernel/sched.c 2006-03-18 05:22:21.000000000 +0100
@@ -685,6 +685,16 @@
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
+ /*
+ * On SMP systems, a task can go to sleep on one CPU and
+ * wake up on another. When this happens, the timestamp
+ * is rounded to the nearest tick, which can lead to now
+ * being less than p->timestamp for short sleeps. Ignore
+ * these, they're insignificant.
+ */
+ if (unlikely(now < p->timestamp))
+ __sleep_time = 0ULL;
+
if (unlikely(p->policy == SCHED_BATCH))
sleep_time = 0;
else {
prev parent reply other threads:[~2006-03-18 4:40 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-18 4:37 [2.6.16-rc6 patch] smp fix for recalc_task_prio() Mike Galbraith
2006-03-18 4:41 ` Mike Galbraith [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1142656901.8262.13.camel@homer \
--to=efault@gmx.de \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox