Re: 2.6.15-rc5-rt4: BUG: swapper:0 task might have lost a preemptioncheck!
From: K.R. Foley
Date: Fri Dec 23 2005 - 11:31:41 EST
Steven Rostedt wrote:
> On Thu, 2005-12-22 at 21:14 -0600, K.R. Foley wrote:
>> Lee Revell wrote:
>>> Got this on boot. Same .config as the last one I sent you.
>>>
>>> VP_IDE: VIA vt8235 (rev 00) IDE UDMA133 controller on pci0000:00:11.1
>>> ide1: BM-DMA at 0xe008-0xe00f, BIOS settings: hdc:DMA, hdd:pio
>>> Probing IDE interface ide1...
>>> BUG: swapper:0 task might have lost a preemption check!
>>> [<c010440c>] dump_stack+0x1c/0x20 (20)
>>> [<c01166aa>] preempt_enable_no_resched+0x5a/0x60 (20)
>>> [<c0100dd9>] cpu_idle+0x79/0xb0 (12)
>>> [<c0100280>] _stext+0x40/0x50 (28)
>>> [<c03078e6>] start_kernel+0x176/0x1d0 (20)
>>> [<c0100199>] 0xc0100199 (1086889999)
>>> ---------------------------
>>> | preempt count: 00000000 ]
>>> | 0-level deep critical section nesting:
>>> ----------------------------------------
>>>
>>>
>
>
> OK, I just found an SMP bug, and here's the patch. Maybe this will help
> you kr. I'm currently running x86_64 SMP with 2.6.15-rc5-rt4 with this
> and my softirq-no-hrtimers patch I sent earlier.
>
> -- Steve
>
> Index: linux-2.6.15-rc5-rt4/kernel/workqueue.c
> ===================================================================
> --- linux-2.6.15-rc5-rt4.orig/kernel/workqueue.c 2005-12-23 10:23:25.000000000 -0500
> +++ linux-2.6.15-rc5-rt4/kernel/workqueue.c 2005-12-23 10:25:21.000000000 -0500
> @@ -370,10 +370,17 @@
> void set_workqueue_thread_prio(struct workqueue_struct *wq, int cpu,
> int policy, int rt_priority, int nice)
> {
> - struct task_struct *p = wq->cpu_wq[cpu].thread;
> + struct cpu_workqueue_struct *cwq;
> + struct task_struct *p;
> struct sched_param param = { .sched_priority = rt_priority };
> + unsigned long flags;
> int ret;
>
> + cwq = per_cpu_ptr(wq->cpu_wq, cpu);
> + spin_lock_irqsave(&cwq->lock, flags);
> + p = cwq->thread;
> + spin_unlock_irqrestore(&cwq->lock, flags);
> +
> set_user_nice(p, nice);
> ret = sys_sched_setscheduler(p->pid, policy, ¶m);
> if (ret)
>
>
>
OK. The BUG still exists (output below) but it does boot now with the
above patch applied (THANKS Steven!), which would seem to imply the two
weren't related. ARGH! :)
Dec 23 10:16:27 porky kernel: Event source lapic installed with caps set: 06
Dec 23 10:16:27 porky kernel: BUG: swapper:0 task might have lost a
preemption check!
Dec 23 10:16:27 porky kernel: Brought up 2 CPUs
Dec 23 10:16:27 porky kernel: checking if image is initramfs... it is
Dec 23 10:16:27 porky kernel: [<c010424e>] dump_stack+0x1e/0x20 (20)
Dec 23 10:16:27 porky kernel: [<c011c9cf>]
preempt_enable_no_resched+0x5f/0x70 (20)
Dec 23 10:16:27 porky kernel: [<c0100ff2>] cpu_idle+0xb2/0x100 (40)
Dec 23 10:16:27 porky kernel: [<c0111446>]
start_secondary+0x296/0x340<6>Freeing initrd memory: 452k freed
--
kr
-
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