[patch] suspend debugging: simulate suspend-to-RAM

[patch] suspend debugging: simulate suspend-to-RAM

[Ingo Molnar]

Subject: [patch] suspend debugging: simulate suspend-to-RAM
From: Ingo Molnar <mingo@elte.hu>

most resume bugs are due to the kernel hanging or crashing while trying 
to resume a specific device. It is extremely hard to debug such hangs 
because often when the hang happens there's no console available yet.

Make debugging such bugs easier by offering a resume mode that does not 
actually call into the BIOS to turn off the machine. This, in 
combination with earlyprintk=serial,ttyS0,115200,keep , 
CONFIG_PM_DEBUG=y, CONFIG_DISABLE_CONSOLE_SUSPEND=y and 
/sys/power/filter enables me to have a fully functional serial console 
during the full suspend/resume cycle.

I debugged two suspend bugs in the -rt kernel this way already, so it's 
pretty useful.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 Documentation/kernel-parameters.txt |    4 ++++
 drivers/acpi/sleep/main.c           |   15 ++++++++++++++-
 include/linux/acpi.h                |    1 +
 kernel/sysctl.c                     |   16 ++++++++++++++++
 4 files changed, 35 insertions(+), 1 deletion(-)

Index: linux/Documentation/kernel-parameters.txt
===================================================================
--- linux.orig/Documentation/kernel-parameters.txt
+++ linux/Documentation/kernel-parameters.txt
@@ -159,6 +159,10 @@ and is between 256 and 4096 characters. 
 
 	acpi_osi=	[HW,ACPI] empty param disables _OSI
 
+	acpi_simulate_suspend_to_ram
+			[KNL] Do not call into BIOS to do suspend-to-RAM
+			Format: <0/1>
+
 	acpi_serialize	[HW,ACPI] force serialization of AML methods
 
 	acpi_skip_timer_override [HW,ACPI]
Index: linux/drivers/acpi/sleep/main.c
===================================================================
--- linux.orig/drivers/acpi/sleep/main.c
+++ linux/drivers/acpi/sleep/main.c
@@ -35,6 +35,14 @@ static u32 acpi_suspend_states[] = {
 
 static int init_8259A_after_S1;
 
+/*
+ * simulate entry into the BIOS - this way the system will not
+ * be turned off for real, and the kernel's resume functionality
+ * can be debugged while still having some system capabilities
+ * left. This is especially useful in combination with /sys/power/filter.
+ */
+int acpi_simulate_suspend_to_ram;
+
 /**
  *	acpi_pm_prepare - Do preliminary suspend work.
  *	@pm_state:		suspend state we're entering.
@@ -91,7 +99,12 @@ static int acpi_pm_enter(suspend_state_t
 		break;
 
 	case PM_SUSPEND_MEM:
-		do_suspend_lowlevel();
+		if (unlikely(acpi_simulate_suspend_to_ram)) {
+			printk(KERN_INFO "ACPI: simulating suspend-to-RAM: "
+					 "not calling BIOS.\n");
+		} else {
+			do_suspend_lowlevel();
+		}
 		break;
 
 	case PM_SUSPEND_DISK:
Index: linux/include/linux/acpi.h
===================================================================
--- linux.orig/include/linux/acpi.h
+++ linux/include/linux/acpi.h
@@ -438,6 +438,7 @@ extern int pci_mmcfg_config_num;
 
 extern int sbf_port;
 extern unsigned long acpi_video_flags;
+extern int acpi_simulate_suspend_to_ram;
 
 #else	/* !CONFIG_ACPI */
 
Index: linux/kernel/sysctl.c
===================================================================
--- linux.orig/kernel/sysctl.c
+++ linux/kernel/sysctl.c
@@ -329,6 +329,14 @@ static ctl_table kern_table[] = {
 		.proc_handler	= &proc_dointvec,
 	},
 	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "futex_performance_hack",
+		.data		= &futex_performance_hack,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
 		.ctl_name	= KERN_PANIC,
 		.procname	= "prof_pid",
 		.data		= &prof_pid,
@@ -908,6 +916,14 @@ static ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_doulongvec_minmax,
 	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "acpi_simulate_suspend_to_ram",
+		.data		= &acpi_simulate_suspend_to_ram,
+		.maxlen		= sizeof (int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
 #endif
 #ifdef CONFIG_IA64
 	{

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Pavel Machek]

Hi!

> Subject: [patch] suspend debugging: simulate suspend-to-RAM
> From: Ingo Molnar <mingo@elte.hu>
> 
> most resume bugs are due to the kernel hanging or crashing while trying 
> to resume a specific device. It is extremely hard to debug such hangs 
> because often when the hang happens there's no console available
> yet.

While the functionality is useful, no I do not think this should be
configured by sysctl or kernel parameter.

Perhaps right interface is "echo fake-mem > /sys/power/state"? 

								Pavel

> Index: linux/kernel/sysctl.c
> ===================================================================
> --- linux.orig/kernel/sysctl.c
> +++ linux/kernel/sysctl.c
> @@ -329,6 +329,14 @@ static ctl_table kern_table[] = {
>  		.proc_handler	= &proc_dointvec,
>  	},
>  	{
> +		.ctl_name	= CTL_UNNUMBERED,
> +		.procname	= "futex_performance_hack",
> +		.data		= &futex_performance_hack,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= &proc_dointvec,
> +	},
> +	{
>  		.ctl_name	= KERN_PANIC,
>  		.procname	= "prof_pid",
>  		.data		= &prof_pid,

Leftover hunk?


-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Rafael J. Wysocki]

On Thursday, 25 January 2007 14:07, Pavel Machek wrote:
> Hi!
> 
> > Subject: [patch] suspend debugging: simulate suspend-to-RAM
> > From: Ingo Molnar <mingo@elte.hu>
> > 
> > most resume bugs are due to the kernel hanging or crashing while trying 
> > to resume a specific device. It is extremely hard to debug such hangs 
> > because often when the hang happens there's no console available
> > yet.
> 
> While the functionality is useful, no I do not think this should be
> configured by sysctl or kernel parameter.
> 
> Perhaps right interface is "echo fake-mem > /sys/power/state"? 

Yes, the "test" and "testproc" debug modes are started via /sys/power/state,
so let's make it consistent.

Greetings,
Rafael

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Pavel Machek]

On Thu 2007-01-25 14:29:24, Rafael J. Wysocki wrote:
> On Thursday, 25 January 2007 14:07, Pavel Machek wrote:
> > Hi!
> > 
> > > Subject: [patch] suspend debugging: simulate suspend-to-RAM
> > > From: Ingo Molnar <mingo@elte.hu>
> > > 
> > > most resume bugs are due to the kernel hanging or crashing while trying 
> > > to resume a specific device. It is extremely hard to debug such hangs 
> > > because often when the hang happens there's no console available
> > > yet.
> > 
> > While the functionality is useful, no I do not think this should be
> > configured by sysctl or kernel parameter.
> > 
> > Perhaps right interface is "echo fake-mem > /sys/power/state"? 
> 
> Yes, the "test" and "testproc" debug modes are started via /sys/power/state,
> so let's make it consistent.

Ok, so this one should be "testmem".
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Andrey Borzenkov]

Ingo Molnar wrote:
> Make debugging such bugs easier by offering a resume mode that does not
> actually call into the BIOS to turn off the machine. This, in
> combination with earlyprintk=serial,ttyS0,115200,keep ,
> CONFIG_PM_DEBUG=y, CONFIG_DISABLE_CONSOLE_SUSPEND=y and
> /sys/power/filter enables me to have a fully functional serial console
> during the full suspend/resume cycle.
>

Will it work with netconsole too? COM port is often missing in notebooks
today.

-andrey

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Matt Mackall]

On Thu, Jan 25, 2007 at 09:03:22PM +0300, Andrey Borzenkov wrote:
> Ingo Molnar wrote:
> > Make debugging such bugs easier by offering a resume mode that does not
> > actually call into the BIOS to turn off the machine. This, in
> > combination with earlyprintk=serial,ttyS0,115200,keep ,
> > CONFIG_PM_DEBUG=y, CONFIG_DISABLE_CONSOLE_SUSPEND=y and
> > /sys/power/filter enables me to have a fully functional serial console
> > during the full suspend/resume cycle.
> >
> 
> Will it work with netconsole too? COM port is often missing in notebooks
> today.

Should, if you add your network device to the aforementioned filter.

-- 
Mathematics is the supreme nostalgia of our time.

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Rafael J. Wysocki]

On Thursday, 25 January 2007 22:26, Matt Mackall wrote:
> On Thu, Jan 25, 2007 at 09:03:22PM +0300, Andrey Borzenkov wrote:
> > Ingo Molnar wrote:
> > > Make debugging such bugs easier by offering a resume mode that does not
> > > actually call into the BIOS to turn off the machine. This, in
> > > combination with earlyprintk=serial,ttyS0,115200,keep ,
> > > CONFIG_PM_DEBUG=y, CONFIG_DISABLE_CONSOLE_SUSPEND=y and
> > > /sys/power/filter enables me to have a fully functional serial console
> > > during the full suspend/resume cycle.
> > >
> > 
> > Will it work with netconsole too? COM port is often missing in notebooks
> > today.
> 
> Should, if you add your network device to the aforementioned filter.

Hm, what about the bus to which the device is connected?

Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Andi Kleen]

Andrey Borzenkov <arvidjaar@mail.ru> writes:

> Will it work with netconsole too? COM port is often missing in notebooks
> today.

It will work with some luck with firescope (in the worst case you
might need to disable suspend in ochi1394). Many laptops have firewire
ports.

ftp://ftp.firstfloor.org/pub/ak/firescope/

-Andi
 

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Ingo Molnar]

* Andi Kleen <ak@suse.de> wrote:

> Andrey Borzenkov <arvidjaar@mail.ru> writes:
> 
> > Will it work with netconsole too? COM port is often missing in notebooks
> > today.
> 
> It will work with some luck with firescope (in the worst case you
> might need to disable suspend in ochi1394). Many laptops have firewire
> ports.
> 
> ftp://ftp.firstfloor.org/pub/ak/firescope/

wow, that's really neat!

	Ingo

Re: [patch] suspend debugging: simulate suspend-to-RAM

[Andi Kleen]

On Wednesday 31 January 2007 10:12, Ingo Molnar wrote:
> 
> * Andi Kleen <ak@suse.de> wrote:
> 
> > Andrey Borzenkov <arvidjaar@mail.ru> writes:
> > 
> > > Will it work with netconsole too? COM port is often missing in notebooks
> > > today.
> > 
> > It will work with some luck with firescope (in the worst case you
> > might need to disable suspend in ochi1394). Many laptops have firewire
> > ports.
> > 
> > ftp://ftp.firstfloor.org/pub/ak/firescope/
> 
> wow, that's really neat!

To give proper credit firescope originally came from Ben Herrenschmidt
for PPC. I just ported it to x86 with a few changes.

BTW if you like firescope you might also like fireproxy
http://www.suse.de/~bk/firewire/

There's also a early ohci1394 driver in there to make
firescope/fireproxy work earlier during boot, but it's still somewhat
experimental.

-Andi