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From: Thomas Gleixner <tglx@linutronix.de>
To: Borislav Petkov <bp@alien8.de>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	Dave Hansen <dave@sr71.net>, LKML <linux-kernel@vger.kernel.org>,
	Dave Jones <davej@redhat.com>,
	dhillf@gmail.com, Peter Zijlstra <peterz@infradead.org>
Subject: Re: kernel BUG at kernel/smpboot.c:134!
Date: Mon, 8 Apr 2013 11:24:14 +0200 (CEST)
Message-ID: <alpine.LFD.2.02.1304081122040.21884@ionos> (raw)
In-Reply-To: <20130407095025.GA31307@pd.tnic>

On Sun, 7 Apr 2013, Borislav Petkov wrote:

> On Sun, Apr 07, 2013 at 11:20:10AM +0200, Thomas Gleixner wrote:
> > And it's even more bogus because the cpu to which we would bind in
> > kthread_create_on_cpu() is not yet online.
> 
> In case you guys are wondering about reproducibility, I saw the same
> BUG_ON yesterday on a 32-bit atom smp qemu guest too (don't ask why?
> :-))

I don't have to ask. It's caused by massive brain failure on my side.

Does the patch below fix the issue ?

Thanks,

	tglx
---
Index: linux-2.6/kernel/kthread.c
===================================================================
--- linux-2.6.orig/kernel/kthread.c
+++ linux-2.6/kernel/kthread.c
@@ -131,8 +131,14 @@ static void __kthread_parkme(struct kthr
 		schedule();
 		__set_current_state(TASK_INTERRUPTIBLE);
 	}
-	clear_bit(KTHREAD_IS_PARKED, &self->flags);
 	__set_current_state(TASK_RUNNING);
+	clear_bit(KTHREAD_IS_PARKED, &self->flags);
+
+	/* Rebind ourself to the target cpu */
+	if (test_bit(KTHREAD_IS_PER_CPU, &self->flags)) {
+		set_cpus_allowed_ptr(currrent, cpumask_of(self->cpu));
+		current->flags |= PF_THREAD_BOUND;
+	}
 }
 
 void kthread_parkme(void)
@@ -344,11 +350,8 @@ void kthread_unpark(struct task_struct *
 		 * park before that happens we'd see the IS_PARKED bit
 		 * which might be about to be cleared.
 		 */
-		if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
-			if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
-				__kthread_bind(k, kthread->cpu);
+		if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags))
 			wake_up_process(k);
-		}
 	}
 	put_task_struct(k);
 }

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-05 21:43 Dave Hansen
2013-04-06  7:12 ` Srivatsa S. Bhat
2013-04-06  8:31   ` Thomas Gleixner
2013-04-07  9:20     ` Thomas Gleixner
2013-04-07  9:50       ` Borislav Petkov
2013-04-08  9:24         ` Thomas Gleixner [this message]
2013-04-08 11:55           ` Borislav Petkov
2013-04-08 12:17             ` Thomas Gleixner
2013-04-09 14:38               ` [PATCH] kthread: Prevent unpark race which puts threads on the wrong cpu Thomas Gleixner
2013-04-09 15:55                 ` Dave Hansen
2013-04-09 18:43                   ` Thomas Gleixner
2013-04-09 19:30                     ` Thomas Gleixner
2013-04-09 20:38                       ` Dave Hansen
2013-04-09 20:54                         ` Dave Hansen
2013-04-10  8:29                         ` Thomas Gleixner
2013-04-10 10:51                           ` Thomas Gleixner
2013-04-10 19:41                             ` Dave Hansen
2013-04-11 10:19                               ` Thomas Gleixner
2013-04-11 10:48                                 ` Srivatsa S. Bhat
2013-04-11 11:43                                   ` Srivatsa S. Bhat
2013-04-11 11:59                                     ` Srivatsa S. Bhat
2013-04-11 12:51                                     ` Thomas Gleixner
2013-04-11 12:54                                     ` Thomas Gleixner
2013-04-11 13:46                                   ` Thomas Gleixner
2013-04-11 18:07                                 ` Dave Hansen
2013-04-11 19:48                                   ` Thomas Gleixner
2013-04-10 14:03                   ` [PATCH] CPU hotplug, smpboot: Fix crash in smpboot_thread_fn() Srivatsa S. Bhat
2013-04-11  8:10                     ` Thomas Gleixner
2013-04-11 10:19                       ` Srivatsa S. Bhat
2013-04-11 19:16                 ` [PATCH] kthread: Prevent unpark race which puts threads on the wrong cpu Srivatsa S. Bhat
2013-04-11 20:47                   ` Thomas Gleixner
2013-04-11 21:19                     ` Srivatsa S. Bhat
2013-04-12 10:59                       ` Thomas Gleixner
2013-04-12 11:26                         ` Srivatsa S. Bhat
2013-04-15 19:49                         ` Dave Hansen
2013-04-12 10:41                 ` Peter Zijlstra
2013-04-12 12:32                 ` [tip:core/urgent] " tip-bot for Thomas Gleixner
2014-09-23  0:09 kernel BUG at kernel/smpboot.c:134! Brian Norris

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