Keep the HPET-based hardlockup detector disabled unless explicitly enabled
via a command-line argument. If such parameter is not given, the
initialization of the HPET-based hardlockup detector fails and the NMI
watchdog will fall back to use the perf-based implementation.
Implement the command-line parsing using an early_param, as
__setup("nmi_watchdog=") only parses generic options.
Cc: Andi Kleen <a...@linux.intel.com>
Cc: Stephane Eranian <eran...@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shan...@intel.com>
Cc: io...@lists.linux-foundation.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: x...@kernel.org
Reviewed-by: Tony Luck <tony.l...@intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
--
Changes since v5:
* None
Changes since v4:
* None
Changes since v3:
* None
Changes since v2:
* Do not imply that using nmi_watchdog=hpet means the detector is
enabled. Instead, print a warning in such case.
Changes since v1:
* Added documentation to the function handing the nmi_watchdog
kernel command-line argument.
---
.../admin-guide/kernel-parameters.txt | 8 ++++++-
arch/x86/kernel/watchdog_hld_hpet.c | 22 +++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index 269be339d738..89eae950fdb8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3370,7 +3370,7 @@
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
@@ -3381,6 +3381,12 @@
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,
+ it falls back to the default implementation (perf or
+ architecture-specific). Specifying hpet has no effect
+ if the NMI watchdog is not enabled (either at build time
+ or via the command line).
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 3effdbf29095..4413d5fb94f4 100644
--- a/arch/x86/kernel/watchdog_hld_hpet.c
+++ b/arch/x86/kernel/watchdog_hld_hpet.c
@@ -379,6 +379,28 @@ void hardlockup_detector_hpet_start(void)
enable_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 (!str)
+ return -EINVAL;
+
+ if (parse_option_str(str, "hpet"))
+ hardlockup_use_hpet = true;
+
+ if (!nmi_watchdog_user_enabled && hardlockup_use_hpet)
+ pr_err("Selecting HPET NMI watchdog has no effect with NMI
watchdog disabled\n");
+
+ return 0;
+}
+early_param("nmi_watchdog", hardlockup_detector_hpet_setup);
+
/**
* hardlockup_detector_hpet_init() - Initialize the hardlockup detector
*
--
2.17.1
