linux-kernel - Re: spinlock lockup on CPU#0

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Message-Id: <20080426112907.77613dee.akpm@linux-foundation.org>
Date:	Sat, 26 Apr 2008 11:29:07 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Justin Mattock" <justinmattock@...il.com>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: spinlock lockup on CPU#0

On Thu, 24 Apr 2008 01:41:32 +0000 "Justin Mattock" <justinmattock@...il.com> wrote:

> Hello, I recorded a .mov of a spinlock, but cant seem to send it out,
> so I have to manually write it down:
> 
> BUG: spinlock lockup on CPU#0, swapper/0, c17fa6c0
> Pid: 0. swapper Not tainted 2.6.25-03562-g3dc5063 #1
> [<c0219fbb>]  _raw_spin_lock+0xd5/0xf9
> [<c0377c6b>] _spin_lock+0x8/0xa
> [<c011cdce>]  task_rq_lock+0x44/0x6b
> [<c011cfb4>]   try_to_wake+0x2a/0x1c4
> [<co11d159>]  default_wake_function+0xb/0xd
> [<co118847>] __wake_up_common+0x2f/0x5a
> [<c011bc11>] complete+0x2b/0x3e
> [<c02ad79a>] usb_api_blocking_completion+0x13/0x15
> [<c02abadc>] usb_hcd_giveback_urb+0x52/0x82
> [<f88686c7>] ehci_urb_done+0x6f/0x7c [ehci_hcd]
> [<f8869614>] qh_completions+0x2d7/0x348 [ehci_hcd]
> [<f8869721>] ehci_work+0x9c [ehci_hcd]
> [<c0107c35>] ? sched_clock+0xb/0x1c
> [<c0119bec>] ? __update_rq_clock+0x94/0x15a
> [<f886c827>] ehci_irq+0x138/0x15f [ehci_hcd]
> [<c02abd9> ] usb_hcd_irq+0x23/0x51
> [<c0151c43>] handle_IRQ_event+0x2a/0x5a
> [<c0152d2c>] handle_fasteoi_irq+0x74/0xb6
> [<c01058c5>] do_IRQ+0x71/0x8c
> [<c01042f7>] common_interrupt+0x23/0x28
> [<c011fb07>] ? sched_clock_idle_wakeup_event+0x5b/0x74
> [<c02cc212>] acpi_idle_enter_bm+0x2a4/0x31f    [processor]
> [<c02cc212>] cpuidle_idle_call+0x5c/0x8c
> [<c02cc1b4>] ? cpuidle_idle_call+0x0/0x8c
> [<c0102571>] cpu_idle+0xb1/0xd1
> [<c036b371>] reset_init+0x49/0x4b
> =====================================================
> 
> 
> Hopefully the numbers are right, and hopefully this provides enough
> info to help the kernel out

Well that's cute.  At a guess I'd say that acpi_processor_idle() managed to
call sched_clock_idle_wakeup_event() with local interrupts enabled.  We
took an interrupt with rq->lock held and things went downhill from there.

Can you add this please, see if it triggers?


--- a/kernel/sched.c~a
+++ a/kernel/sched.c
@@ -811,6 +811,7 @@ void sched_clock_idle_sleep_event(void)
 {
 	struct rq *rq = cpu_rq(smp_processor_id());
 
+	WARN_ON(!irqs_disabled());
 	spin_lock(&rq->lock);
 	__update_rq_clock(rq);
 	spin_unlock(&rq->lock);
@@ -826,6 +827,7 @@ void sched_clock_idle_wakeup_event(u64 d
 	struct rq *rq = cpu_rq(smp_processor_id());
 	u64 now = sched_clock();
 
+	WARN_ON(!irqs_disabled());
 	rq->idle_clock += delta_ns;
 	/*
 	 * Override the previous timestamp and ignore all
_

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