Re: [RFC PATCH v2 13/14] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter
On Tue, Mar 26, 2019 at 10:29:52PM +0100, Thomas Gleixner wrote:
> On Wed, 27 Feb 2019, Ricardo Neri wrote:
> > + 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. Specifying
> > + hpet implies that nmi_watchdog is on.
>
> How so?
>
I meant to say that the user does not need to provide nmi_watchdog=1 and
nmi_watchdog=hpet separately.
I think this is true because watchdog_user_enabled in kernel/watchdog.c is set
to 1 when CONFIG_HARDLOCKUP_DETECTOR is selected. Also, if
nmi_watchdog_available
is set to true if watchdog_nmi_probe() is successful.
Perhaps I can add a warning in case nmi_watchdog=hpet and either
CONFIG_HARDLOCKUP_DETECTOR or CONFIG_HARDLOCKUP_DETECTOR_HPET are not
selected?
> > +static int __init hardlockup_detector_hpet_setup(char *str)
> > +{
> > + if (strstr(str, "hpet"))
> > + hardlockup_use_hpet = true;
>
> strstr()? Not really.
Is strncmp(str, "hpet", 5) more acceptable?
>
> > +
> > + return 0;
> > +}
> > +__setup("nmi_watchdog=", hardlockup_detector_hpet_setup);
> > +
> > /**
> > * hardlockup_detector_hpet_init() - Initialize the hardlockup detector
> > *
> > @@ -405,6 +422,9 @@ int __init hardlockup_detector_hpet_init(void)
> > {
> > int ret;
> >
> > + if (!hardlockup_use_hpet)
> > + return -ENODEV;
>
> This should have been there in the patch which introduces
> hardlockup_detector_hpet_init(). And this patch merily adds the command
> line magic which sets that flag.
Sure, I will move this check into the patch that introduces
hardlockup_detector_hpet_init().
>
> > +
> > if (!is_hpet_enabled())
> > return -ENODEV;
> >
> > diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> > index 367aa81294ef..28cad7310378 100644
> > --- a/kernel/watchdog.c
> > +++ b/kernel/watchdog.c
> > @@ -78,7 +78,7 @@ 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;
>
> Why?
My understanding is that this is needed so that other __setup functions that
also
want to check "nmi_watchdog" are able to do it. Is this understanding
not correct?
Thanks and BR,
Ricardo
Re: [RFC PATCH v2 13/14] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter
On Wed, 27 Feb 2019, Ricardo Neri wrote:
> + 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. Specifying
> + hpet implies that nmi_watchdog is on.
How so?
> +static int __init hardlockup_detector_hpet_setup(char *str)
> +{
> + if (strstr(str, "hpet"))
> + hardlockup_use_hpet = true;
strstr()? Not really.
> +
> + return 0;
> +}
> +__setup("nmi_watchdog=", hardlockup_detector_hpet_setup);
> +
> /**
> * hardlockup_detector_hpet_init() - Initialize the hardlockup detector
> *
> @@ -405,6 +422,9 @@ int __init hardlockup_detector_hpet_init(void)
> {
> int ret;
>
> + if (!hardlockup_use_hpet)
> + return -ENODEV;
This should have been there in the patch which introduces
hardlockup_detector_hpet_init(). And this patch merily adds the command
line magic which sets that flag.
> +
> if (!is_hpet_enabled())
> return -ENODEV;
>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 367aa81294ef..28cad7310378 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -78,7 +78,7 @@ 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;
Why?
Thanks,
tglx
[RFC PATCH v2 13/14] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter
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: "H. Peter Anvin"
Cc: Ashok Raj
Cc: Andi Kleen
Cc: Tony Luck
Cc: Peter Zijlstra
Cc: Clemens Ladisch
Cc: Arnd Bergmann
Cc: Philippe Ombredanne
Cc: Kate Stewart
Cc: "Rafael J. Wysocki"
Cc: Mimi Zohar
Cc: Jan Kiszka
Cc: Nick Desaulniers
Cc: Masahiro Yamada
Cc: Nayna Jain
Cc: "Ravi V. Shankar"
Cc: x...@kernel.org
Signed-off-by: Ricardo Neri
--
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.
---
.../admin-guide/kernel-parameters.txt | 6 +-
arch/x86/kernel/watchdog_hld_hpet.c | 20 +++
kernel/watchdog.c | 2 +-
3 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index cf8f5877d85f..c6270ddeb130 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2739,7 +2739,7 @@
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
@@ -2749,6 +2749,10 @@
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. Specifying
+ hpet implies that nmi_watchdog is on.
These settings can be accessed at runtime via
the nmi_watchdog and hardlockup_panic sysctls.
diff --git a/arch/x86/kernel/watchdog_hld_hpet.c
b/arch/x86/kernel/watchdog_hld_hpet.c
index 65b4699f249a..4402deff4b77 100644
--- a/arch/x86/kernel/watchdog_hld_hpet.c
+++ b/arch/x86/kernel/watchdog_hld_hpet.c
@@ -20,6 +20,7 @@
#include
static struct hpet_hld_data *hld_data;
+static bool hardlockup_use_hpet;
/**
* get_count() - Get the current count of the HPET timer
@@ -391,6 +392,22 @@ void hardlockup_detector_hpet_stop(void)
disable_timer(hld_data);
}
+/**
+ * hardlockup_detector_hpet_setup() - Parse command-line parameters
+ * @str: A string containing the kernel command line
+ *
+ * Parse the nmi_watchdog parameter from the kernel command line. If
+ * selected by the user, use this implementation to detect hardlockups.
+ */
+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
*
@@ -405,6 +422,9 @@ int __init hardlockup_detector_hpet_init(void)
{
int ret;
+ if (!hardlockup_use_hpet)
+ return -ENODEV;
+
if (!is_hpet_enabled())
return -ENODEV;
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 367aa81294ef..28cad7310378 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -78,7 +78,7 @@ 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);
--
2.17.1
