[RFC,22/23] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter

Message ID 1528851463-21140-23-git-send-email-ricardo.neri-calderon@linux.intel.com
State Not Applicable
Delegated to: David Miller
Headers show
Series
  • Implement an HPET-based hardlockup detector
Related show

Commit Message

Ricardo Neri June 13, 2018, 12:57 a.m.
Keep the HPET-based hardlockup detector disabled unless explicitly enabled
via a command line argument. If such parameter is not given, the hardlockup
detector will fallback to use the perf-based implementation.

The function hardlockup_panic_setup() is updated to return 0 in order to
to allow __setup functions of specific hardlockup detectors (in this case
hardlockup_detector_hpet_setup()) to inspect the nmi_watchdog boot
parameter.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jacob Pan <jacob.jun.pan@intel.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Babu Moger <babu.moger@oracle.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Christoffer Dall <cdall@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
--
checkpatch gives the following warning:

CHECK: __setup appears un-documented -- check Documentation/admin-guide/kernel-parameters.rst
+__setup("nmi_watchdog=", hardlockup_detector_hpet_setup);

This is a false-positive as the option nmi_watchdog is already
documented. The option is re-evaluated in this file as well.
---
 Documentation/admin-guide/kernel-parameters.txt |  5 ++++-
 kernel/watchdog.c                               |  2 +-
 kernel/watchdog_hld_hpet.c                      | 13 +++++++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)

Comments

Randy Dunlap June 13, 2018, 5:26 a.m. | #1
On 06/12/2018 05:57 PM, Ricardo Neri wrote:
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index f2040d4..a8833c7 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2577,7 +2577,7 @@
>  			Format: [state][,regs][,debounce][,die]
>  
>  	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
> -			Format: [panic,][nopanic,][num]
> +			Format: [panic,][nopanic,][num,][hpet]
>  			Valid num: 0 or 1
>  			0 - turn hardlockup detector in nmi_watchdog off
>  			1 - turn hardlockup detector in nmi_watchdog on

This says that I can use "nmi_watchdog=hpet" without using 0 or 1.
Is that correct?

> @@ -2587,6 +2587,9 @@
>  			please see 'nowatchdog'.
>  			This is useful when you use a panic=... timeout and
>  			need the box quickly up again.
> +			When hpet is specified, the NMI watchdog will be driven
> +			by an HPET timer, if available in the system. Otherwise,
> +			the perf-based implementation will be used.
>  
>  			These settings can be accessed at runtime via
>  			the nmi_watchdog and hardlockup_panic sysctls.


thanks,
Ricardo Neri June 14, 2018, 12:58 a.m. | #2
On Tue, Jun 12, 2018 at 10:26:57PM -0700, Randy Dunlap wrote:
> On 06/12/2018 05:57 PM, Ricardo Neri wrote:
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index f2040d4..a8833c7 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2577,7 +2577,7 @@
> >  			Format: [state][,regs][,debounce][,die]
> >  
> >  	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
> > -			Format: [panic,][nopanic,][num]
> > +			Format: [panic,][nopanic,][num,][hpet]
> >  			Valid num: 0 or 1
> >  			0 - turn hardlockup detector in nmi_watchdog off
> >  			1 - turn hardlockup detector in nmi_watchdog on
> 
> This says that I can use "nmi_watchdog=hpet" without using 0 or 1.
> Is that correct?

Yes, this what I meant. In my view, if you set nmi_watchdog=hpet it
implies that you want to activate the NMI watchdog. In this case, perf.

I can see how this will be ambiguous for the case of perf and arch NMI
watchdogs.

Alternative, a new parameter could be added; such as nmi_watchdog_type. I
didn't want to add it in this patchset as I think that a single parameter
can handle the enablement and type of the NMI watchdog.

What do you think?

Thanks and BR,
Ricardo
--
To unsubscribe from this list: send the line "unsubscribe sparclinux" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Randy Dunlap June 14, 2018, 3:30 a.m. | #3
On 06/13/2018 05:58 PM, Ricardo Neri wrote:
> On Tue, Jun 12, 2018 at 10:26:57PM -0700, Randy Dunlap wrote:
>> On 06/12/2018 05:57 PM, Ricardo Neri wrote:
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>> index f2040d4..a8833c7 100644
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -2577,7 +2577,7 @@
>>>  			Format: [state][,regs][,debounce][,die]
>>>  
>>>  	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
>>> -			Format: [panic,][nopanic,][num]
>>> +			Format: [panic,][nopanic,][num,][hpet]
>>>  			Valid num: 0 or 1
>>>  			0 - turn hardlockup detector in nmi_watchdog off
>>>  			1 - turn hardlockup detector in nmi_watchdog on
>>
>> This says that I can use "nmi_watchdog=hpet" without using 0 or 1.
>> Is that correct?
> 
> Yes, this what I meant. In my view, if you set nmi_watchdog=hpet it
> implies that you want to activate the NMI watchdog. In this case, perf.
> 
> I can see how this will be ambiguous for the case of perf and arch NMI
> watchdogs.
> 
> Alternative, a new parameter could be added; such as nmi_watchdog_type. I
> didn't want to add it in this patchset as I think that a single parameter
> can handle the enablement and type of the NMI watchdog.
> 
> What do you think?

I think it's OK like it is.

thanks,

Patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f2040d4..a8833c7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2577,7 +2577,7 @@ 
 			Format: [state][,regs][,debounce][,die]
 
 	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
-			Format: [panic,][nopanic,][num]
+			Format: [panic,][nopanic,][num,][hpet]
 			Valid num: 0 or 1
 			0 - turn hardlockup detector in nmi_watchdog off
 			1 - turn hardlockup detector in nmi_watchdog on
@@ -2587,6 +2587,9 @@ 
 			please see 'nowatchdog'.
 			This is useful when you use a panic=... timeout and
 			need the box quickly up again.
+			When hpet is specified, the NMI watchdog will be driven
+			by an HPET timer, if available in the system. Otherwise,
+			the perf-based implementation will be used.
 
 			These settings can be accessed at runtime via
 			the nmi_watchdog and hardlockup_panic sysctls.
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index b94bbe3..b5ce6e4 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -84,7 +84,7 @@  static int __init hardlockup_panic_setup(char *str)
 		nmi_watchdog_user_enabled = 0;
 	else if (!strncmp(str, "1", 1))
 		nmi_watchdog_user_enabled = 1;
-	return 1;
+	return 0;
 }
 __setup("nmi_watchdog=", hardlockup_panic_setup);
 
diff --git a/kernel/watchdog_hld_hpet.c b/kernel/watchdog_hld_hpet.c
index ebb820d..12e5937 100644
--- a/kernel/watchdog_hld_hpet.c
+++ b/kernel/watchdog_hld_hpet.c
@@ -17,6 +17,7 @@ 
 #define pr_fmt(fmt) "NMI hpet watchdog: " fmt
 
 static struct hpet_hld_data *hld_data;
+static bool hardlockup_use_hpet;
 
 /**
  * get_count() - Get the current count of the HPET timer
@@ -488,6 +489,15 @@  static void hardlockup_detector_hpet_stop(void)
 	spin_unlock(&hld_data->lock);
 }
 
+static int __init hardlockup_detector_hpet_setup(char *str)
+{
+	if (strstr(str, "hpet"))
+		hardlockup_use_hpet = true;
+
+	return 0;
+}
+__setup("nmi_watchdog=", hardlockup_detector_hpet_setup);
+
 /**
  * hardlockup_detector_hpet_init() - Initialize the hardlockup detector
  *
@@ -502,6 +512,9 @@  static int __init hardlockup_detector_hpet_init(void)
 {
 	int ret;
 
+	if (!hardlockup_use_hpet)
+		return -EINVAL;
+
 	if (!is_hpet_enabled())
 		return -ENODEV;