Re: [linux-pm] [PATCH] [suspend] pci_raw_set_power_state: replacemsleep by udelay in resuming procedure

[Wu Zhangjin]

On Fri, 2009-07-17 at 04:33 +0200, Rafael J. Wysocki wrote:
> On Friday 17 July 2009, Wu Zhangjin wrote:
> > Hi,
> > 
> > On Thu, 2009-07-16 at 13:02 -0400, Alan Stern wrote:
> > > On Thu, 16 Jul 2009, Wu Zhangjin wrote:
> > > 
> > > > we can not call msleep() when resuming from STR/Standby: if the
> > > > current_state of the pci device is PCI_D3hot, means we are in the
> > > > procedure of resuming, in this procedure, we can not re-schedule,
> > > > otherwise, there will be a deadlock.
> > > 
> > > I don't understand.
> > > 
> > > First of all, why does current_state == PCI_D3hot mean the system is
> > > resuming from sleep?  Isn't it possible that the PCI device is going
> > > through a runtime resume?
> > > 
> > > Secondly, why will scheduling during a resume cause a deadlock?
> > 
> > Sorry, I'm stupid to make conclusion before describing the problem
> > clearly, here is the problem I encountered:
> > 
> > when I enabled SUSPEND=y in linux-2.6.30.1(with relative patches) on a
> > loongson-based machine(yeeloong laptop,loongson is mips-compatiable), I
> > tried to suspend it via "echo standby > /sys/power/state", with the
> > serial port debugging support, I found it enter into the standby mode
> > successfully. and then, tried to wake it up via the keyboard interrupt,
> > but it stopped at the "Power_up_devices:" of kernel/power/main.c.
> > 
> > here is a short path of this procedure:
> > 
> > suspend_enter:
> > 	...
> > 	device_power_down
> > 	...
> > 	arch_suspend_disable_irqs
> > 	...
> > 	sysdev_suspend
> > 	...
> > 	suspend_ops->enter  (board-specific part)
> > 	...
> > 	sysdev_resume
> > 	...
> > 	arch_suspend_enable_irqs
> > 	...
> > 	device_power_up	 <-----------------------stop here
> > 	...
> > 	
> > and then I continue to trace it:
> > 
> > device_power_up:
> > 	dpm_power_up:
> > 		list_for_each_entry(dev, &dpm_list, power.entry)
> > 			<<DEBUG>>
> >                 if (dev->power.status > DPM_OFF) {
> >                         int error;
> > 
> >                         dev->power.status = DPM_OFF;
> >                         error = resume_device_noirq(dev, state);
> >                         if (error)
> >                                 pm_dev_err(dev, state, " early", error);
> >                 }   
> > 
> > I tried to add prom_putchar() at <<DEBUG>> to print something, and This
> > will make it resume from standby mode successfully. seems,
> > prom_putchar() have influenced the power.status, and make some devices
> > not enter into the condition statement, and make dpm_power_up return
> > directly. (this is very weird, not sure why?)
> > 
> > so, I removed the prom_putchar() from <<DEBUG>>, and it stopped at
> > resume_device_noirq, here is the following tracing path:
> > 	
> > resume_device_noirq:
> >    --> pm_noirq_op
> >    --> ops->resume_noirq (dev) <--> pci_pm_resume_noirq:
> > 	   --> pci_pm_default_resume_noirq
> > 	   --> pci_restore_standard_config
> > 	   --> pci_set_power_state
> >            --> pci_raw_set_power_state
> >            --> msleep    <-----------------------[ stop here]
> > 
> > msleep:
> > 	--> schedule_timeout_uninterruptible
> > 	--> schedule_timeout
> > 	     --> ... 
> > 	     --> __mod_timer
> >              --> ...
> > 	     --> schedule ---> a new scheduling happen and never return
> > 
> > and then I tried to trace schedule(), and even added a prom_putchar() to
> > the end of the schedule() function, it output something successfully,
> > but never return to schedule_timeout(dead? no keyboard response), seems
> > very weird! this is reproductive, perhaps I have missed something here.
> >  
> > so, to avoid this 'weird' situation, I think it's better not to
> > re-schedule in the resuming procedure from standby. and here, I can not
> > find another condition to judge the resuming procedure from standby, so,
> > I use "current_state == PCI_D3hot"(so, my pre-expression is really wrong
> > for it maybe not resume from standby as you indicated). and is there
> > another condition to judge we are resuming from standby? perhaps this is
> > better:
> > 
> >    ((current_state == PCI_D3hot) && (state == PCI_D0))
> > 
> > but seems this also can not indicate we are resuming from standby.
> 
> 'standby' is a system sleep state, while 'current_state' and 'state' refer to
> device power states.
> 
> Anyway, the fact that schedule() did not return in your testing setup indicates
> that there were no timer interrupts delivered to the CPU during resume, which
> should not have happened
> 
> Perhaps it's necessary to annotate your timer interrupts appropriately so that
> they are not disabled during suspend?

Thanks very much, The IRQF_TIMER flag works for me, so the replacement
of msleep by udelay is not needed.

[This source code is not ready to upstream, herein, just a prompt to the
other guys who will meet the same problem.]

[PATCH][loongson] Mark external timer interrupt IRQF_TIMER to prevent
resume failure

This PATCH refers to the commit fee803b2f0c28c78984fc319bd4b88ad47117368
and
the feedback from "Rafael J. Wysocki" <rjw@xxxxxxx> of my patch:
"[suspend]
pci_raw_set_power_state: replace msleep by udelay in resuming procedure"

"timer interrupts are excluded from being disabled during suspend. The
clock
events code manages the disabling of clock events on its own because the
timer
interrupt needs to be functional before the resume code reenables the
device
interrupts."

The external mfgpt timers request their interrupt without setting the
IRQF_TIMER
flag so suspend_device_irqs() disables them as well which results in a
fatal
resume failure on the boot CPU.

Adding IRQF_TIMER to the interupt flags when requesting the mfgpt timer
interrupts solves the problem.

Signed-off-by: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
---
 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/mips/loongson/common/cs5536/cs5536_mfgpt.c
b/arch/mips/loongson/common/cs5536/cs5536_mfgpt.c
index 1a518ec..5b8fa9f 100644
--- a/arch/mips/loongson/common/cs5536/cs5536_mfgpt.c
+++ b/arch/mips/loongson/common/cs5536/cs5536_mfgpt.c
@@ -133,7 +133,7 @@ static irqreturn_t timer_interrupt(int irq, void
*dev_id)
 
 static struct irqaction irq5 = {
 	.handler = timer_interrupt,
-	.flags = IRQF_DISABLED | IRQF_NOBALANCING,
+	.flags = IRQF_TIMER | IRQF_DISABLED | IRQF_NOBALANCING,
 	.name = "timer"
 };
 
-- 
1.6.2.1

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