linux-kernel - Re: rcu stalls seen with numasched

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Date:	Mon, 13 Aug 2012 10:11:28 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
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.

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();
 	}
 

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