linux-kernel - Re: [2.6.30-rc1] RCU detected CPU 1 stall

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Date:	Fri, 10 Apr 2009 07:22:03 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	hugh@...itas.com, jmorris@...ei.org, akpm@...ux-foundation.org
Subject: Re: [2.6.30-rc1] RCU detected CPU 1 stall

On Wed, Apr 08, 2009 at 09:57:35AM +0900, Tetsuo Handa wrote:
> Hello.
> 
> I got this.
> 
> [  161.653269] INFO: RCU detected CPU 1 stall (t=4294932711/32565 jiffies)
> [  161.655376] Pid: 3487, comm: khelper Tainted: G        W  2.6.30-rc1 #1
> [  161.655376] Call Trace:
> [  161.659680]  [<c015949d>] ? printk+0x1d/0x30
> [  161.659680]  [<c01b38b5>] print_cpu_stall+0x45/0xa0
> [  161.663377]  [<c01b39f8>] check_cpu_stall+0xe8/0x190
> [  161.667409]  [<c01ad59d>] ? get_timestamp+0xd/0x20
> [  161.667409]  [<c01b43ab>] __rcu_pending+0x1b/0x160
> [  161.671679]  [<c01b451e>] rcu_pending+0x2e/0x70
> [  161.675680]  [<c01692ab>] update_process_times+0x3b/0x80
> [  161.675680]  [<c018bcf0>] tick_periodic+0x40/0x90
> [  161.679710]  [<c018bd5e>] tick_handle_periodic+0x1e/0xa0
> [  161.679710]  [<c01045e0>] ? apic_timer_interrupt+0x28/0x34
> [  161.683721]  [<c012215f>] local_apic_timer_interrupt+0x6f/0x80
> [  161.687390]  [<c0161184>] ? irq_enter+0x14/0x60
> [  161.691702]  [<c05e7d83>] smp_apic_timer_interrupt+0x33/0x42
> [  161.691702]  [<c01045e7>] apic_timer_interrupt+0x2f/0x34
> [  161.695378]  [<c0225da4>] ? __bprm_mm_init+0xe4/0x120
> [  161.699377]  [<c0379c3d>] ? __get_user_4+0x11/0x17
> [  161.699377]  [<c0225f4e>] ? count+0x3e/0xb0
> [  161.703696]  [<c0228554>] do_execve+0x5f4/0x890
> [  161.707390]  [<c022bd8b>] ? getname+0x6b/0xa0
> [  161.707390]  [<c010237e>] sys_execve+0x5e/0xb0
> [  161.711705]  [<c0103d19>] syscall_call+0x7/0xb
> [  161.711705]  [<c010aee4>] ? kernel_execve+0x24/0x30
> [  161.715395]  [<c0172b6f>] ? ____call_usermodehelper+0xff/0x170
> [  161.719736]  [<c0172a70>] ? ____call_usermodehelper+0x0/0x170
> [  161.723726]  [<c0104707>] ? kernel_thread_helper+0x7/0x10
> 
> Config is at http://I-love.SAKURA.ne.jp/tmp/config-2.6.30-rc1
> Full log is at http://I-love.SAKURA.ne.jp/tmp/dmesg-2.6.30-rc1.txt

CONFIG_PREEMPT_NONE=y
CONFIG_CLASSIC_RCU=y
CONFIG_HZ_250=y

Hmmmm...  This indicates that CPU 1 was spinning in the kernel for
a long time.  At 250 HZ, 32,565 jiffies is 130 seconds, or just over
two -minutes-.  Ouch!!!

The interrupt happened on the stalled CPU, so we know that interrupts
were enabled.  Because we have CONFIG_PREEMPT_NONE=y, there is no
preemption, so preemption need not be disabled.  This could be due
to lock contention, or even a simple infinite loop.

The timer interrupt (apic_timer_interrupt) occurred in either
__bprm_mm_init(), __get_user_4(), count(), or do_execve().  There
have been some recent changes around check_unsafe_exec() -- any
possibility that these introduced excessive lock contention or
an infinite loop?  Ditto for the recent security fixes?

						Thanx, Paul
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