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.
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
Reviewed-by: Tony Luck <tony.l...@intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
--
Changes since v6:
* Do not reuse the nmi_watchdog command line option. Instead, use a
separate command line option. (Nicholas Piggin)
* Document conflict with conflict between `hpet_nmi_watchdog` and
`nohz_full` and dependency on `no_ipi_broadcast`.
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.
---
Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++
arch/x86/kernel/watchdog_hld_hpet.c | 17 +++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index 46268d6baa43..2d1262bb99c7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1708,6 +1708,14 @@
hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
+ hpet_nmi_watchdog [X86, KNL]
+ Drive the NMI watchdog with an HPET channel. This option
+ has no effect if the NMI watchdog is not enabled.
+ The HPET NMI watchdog conflicts with the parameters
+ nohz_full, no_ipi_broadcast, and hpet=disable. If any
+ of these parameters is present the NMI watchdog will
+ fall back to the perf-driven implementation.
+
hugepages= [HW] Number of HugeTLB pages to allocate at boot.
If this follows hugepagesz (below), it specifies
the number of pages of hugepagesz to be allocated.
diff --git a/arch/x86/kernel/watchdog_hld_hpet.c
b/arch/x86/kernel/watchdog_hld_hpet.c
index a03126e02eda..0fc728ad6f15 100644
--- a/arch/x86/kernel/watchdog_hld_hpet.c
+++ b/arch/x86/kernel/watchdog_hld_hpet.c
@@ -39,6 +39,7 @@
#include "apic/local.h"
static struct hpet_hld_data *hld_data;
+static bool hardlockup_use_hpet;
static u64 tsc_next_error;
static void __init setup_hpet_channel(struct hpet_hld_data *hdata)
@@ -366,6 +367,19 @@ 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
+ *
+ * If selected by the user, enable this hardlockup detector.
+ */
+static int __init hardlockup_detector_hpet_setup(char *str)
+{
+ hardlockup_use_hpet = true;
+ return 1;
+}
+__setup("hpet_nmi_watchdog", hardlockup_detector_hpet_setup);
+
static const char hpet_hld_init_failed[] = "Initialization failed:";
/**
@@ -382,6 +396,9 @@ int __init hardlockup_detector_hpet_init(void)
{
int ret;
+ if (!hardlockup_use_hpet)
+ return -ENODEV;
+
if (!is_hpet_enabled()) {
pr_info("%s HPET unavailable\n", hpet_hld_init_failed);
return -ENODEV;
--
2.25.1
