linux-kernel - Re: rcu stalls seen with numasched

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Message-ID: <20120816171609.GA25338@linux.vnet.ibm.com>
Date:	Thu, 16 Aug 2012 22:46:09 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	john stultz <johnstul@...ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: rcu stalls seen with numasched_v2 patches applied.

* Peter Zijlstra <peterz@...radead.org> [2012-08-13 10:11:28]:

> On Mon, 2012-08-13 at 09:51 +0200, Peter Zijlstra wrote:
> > On Fri, 2012-08-10 at 21:54 +0530, Srikar Dronamraju wrote:
> > 
> > > This change worked well on the 2 node machine 
> > > but on the 8 node machine it hangs with repeated messages
> > > 
> > > Pid: 60935, comm: numa01 Tainted: G        W    3.5.0-numasched_v2_020812+ #4
> > > Call Trace:
> > > <IRQ>  [<ffffffff810d32e2>] ? rcu_check_callback s+0x632/0x650
> > > [<ffffffff81061bb8>] ? update_process_times+0x48/0x90
> > > [<ffffffff810a2a4e>] ? tick_sched_timer+0x6e/0xe0
> > > [<ffffffff81079c85>] ? __run_hrtimer+0x75/0x1a0
> > > [<ffffffff810a29e0>] ? tick_setup_sched_timer+0x100/0x100
> > > [<ffffffff8107a036>] ? hrtimer_interrupt+0xf6/0x250
> > > [<ffffffff814f1379>] ? smp_apic_timer_interrupt+0x69/0x99
> > > [<ffffffff814f034a>] ? apic_timer_interrupt+0x6a/0x70
> > > <EOI>  [<ffffffff811082e3>] ? wait_on_page_bit+0x73/0x80
> > > [<ffffffff814e7992>] ? _raw_spin_lock+0x22/0x30
> > > [<ffffffff81131bf3>] ? handle_pte_fault+0x1b3/0xca0
> > > [<ffffffff814e64f7>] ? __schedule+0x2e7/0x710
> > > [<ffffffff8107a9a8>] ? up_read+0x18/0x30
> > > [<ffffffff814eb2be>] ? do_page_fault+0x13e/0x460
> > > [<ffffffff810137ba>] ? __switch_to+0x1aa/0x460
> > > [<ffffffff814e64f7>] ? __schedule+0x2e7/0x710
> > > [<ffffffff814e7de5>] ? page_fault+0x25/0x30
> > > { 3}  (t=62998 jiffies)
> > > 
> > 
> > If you run a -tip kernel without the numa patches, does that work?
> 
> 
> n/m, I found a total brain-fart in there.. does the below sort it?
> 
> ---
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -917,7 +917,7 @@ void task_numa_work(struct callback_head
>  		t = p;
>  		do {
>  			sched_setnode(t, node);
> -		} while ((t = next_thread(p)) != p);
> +		} while ((t = next_thread(t)) != p);
>  		rcu_read_unlock();
>  	}
>  
> 

I tried this fix, but doesnt seem to help.

will try on -tip and revert.

-- 
thanks and regards
srikar

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