LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
	nickpiggin@yahoo.com.au, vatsa@in.ibm.com, clameter@sgi.com,
	tglx@linutronix.de, arjan@linux.intel.com,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC] Patch: dynticks: idle load balancing
Date: Wed, 13 Dec 2006 15:03:14 -0800	[thread overview]
Message-ID: <20061213150314.B12795@unix-os.sc.intel.com> (raw)
In-Reply-To: <20061213231316.GA13849@elte.hu>; from mingo@elte.hu on Thu, Dec 14, 2006 at 12:13:16AM +0100

On Thu, Dec 14, 2006 at 12:13:16AM +0100, Ingo Molnar wrote:
> there's another bug as well: in schedule() resched_cpu() is called with 
> the current runqueue held in two places, which is deadlock potential. 

resched_cpu() was getting called after prepare_task_switch() which
releases the current runqueue lock. Isn't it?

> The easiest fix for this is to use trylock - find the patch for that. 
> This is a hint only anyway - and if a CPU is idle its runqueue will be 

Though I don't see a potential deadlock, I like this optimization.

thanks,
suresh

> lockable. (fixing it via double-locking is easy in the first call site, 
> but the second one looks harder)
> 
> 	Ingo
> 
> Index: linux/kernel/sched.c
> ===================================================================
> --- linux.orig/kernel/sched.c
> +++ linux/kernel/sched.c
> @@ -1167,12 +1167,14 @@ static void resched_task(struct task_str
>  	if (!tsk_is_polling(p))
>  		smp_send_reschedule(cpu);
>  }
> +
>  static void resched_cpu(int cpu)
>  {
>  	struct rq *rq = cpu_rq(cpu);
> -	unsigned int flags;
> +	unsigned long flags;
>  
> -	spin_lock_irqsave(&rq->lock, flags);
> +	if (!spin_trylock_irqsave(&rq->lock, flags))
> +		return;
>  	resched_task(cpu_curr(cpu));
>  	spin_unlock_irqrestore(&rq->lock, flags);
>  }

  reply	other threads:[~2006-12-13 23:39 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-11 23:53 Siddha, Suresh B
2006-12-13 22:43 ` Ingo Molnar
2006-12-13 23:13   ` Ingo Molnar
2006-12-13 23:03     ` Siddha, Suresh B [this message]
2006-12-13 23:31       ` Ingo Molnar
2006-12-13 23:19         ` Siddha, Suresh B
2006-12-14  0:34           ` Ingo Molnar
2006-12-19 20:12           ` Ingo Molnar
2006-12-19 21:12             ` Siddha, Suresh B
2007-01-16 11:35               ` Ingo Molnar
2007-01-30 21:57                 ` Siddha, Suresh B
2007-02-07 22:19                   ` Siddha, Suresh B
2007-02-17  2:03                   ` [patch 1/2] sched: fix idle load balancing in softirqd context Siddha, Suresh B
2007-02-17  2:08                     ` [patch 2/2] sched: dynticks idle load balancing - v2 Siddha, Suresh B
2007-02-21 20:23                       ` Andrew Morton
2007-02-22  3:14                         ` Nick Piggin
2007-02-24  2:01                         ` [patch] sched: dynticks idle load balancing - v3 Siddha, Suresh B
2007-02-22  3:26                       ` [patch 2/2] sched: dynticks idle load balancing - v2 Nick Piggin
2007-02-22 22:33                         ` Siddha, Suresh B
2007-02-23  3:43                           ` Nick Piggin
2007-02-17 14:42                     ` [patch 1/2] sched: fix idle load balancing in softirqd context Steven Rostedt
2007-02-21  6:25                       ` Siddha, Suresh B
2007-02-21 20:13                     ` Andrew Morton
2006-12-13 23:48     ` [RFC] Patch: dynticks: idle load balancing Ingo Molnar
2006-12-20  0:49 ` Steven Rostedt

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=20061213150314.B12795@unix-os.sc.intel.com \
    --to=suresh.b.siddha@intel.com \
    --cc=arjan@linux.intel.com \
    --cc=clameter@sgi.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=nickpiggin@yahoo.com.au \
    --cc=tglx@linutronix.de \
    --cc=vatsa@in.ibm.com \
    --subject='Re: [RFC] Patch: dynticks: idle load balancing' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).