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Subject[RFC PATCH v2 08/14] watchdog/hardlockup: Decouple the hardlockup detector from perf
Date
The current default implementation of the hardlockup detector assumes that
it is implemented using perf events. However, the hardlockup detector can
be driven by other sources of non-maskable interrupts (e.g., a properly
configured timer).

Put in a separate file all the code that is specific to perf: create and
manage events, stop and start the detector. This perf-specific code is put
in the new file watchdog_hld_perf.c

The code generic code used to monitor the timers' thresholds, check
timestamps and detect hardlockups remains in watchdog_hld.c

Functions and variables are simply relocated to a new file. No functional
changes were made.

Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Tony Luck <tony.luck@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: Babu Moger <babu.moger@oracle.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
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: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
kernel/Makefile | 3 +-
kernel/watchdog_hld.c | 153 --------------------------------
kernel/watchdog_hld_perf.c | 175 +++++++++++++++++++++++++++++++++++++
3 files changed, 177 insertions(+), 154 deletions(-)
create mode 100644 kernel/watchdog_hld_perf.c

diff --git a/kernel/Makefile b/kernel/Makefile
index 6aa7543bcdb2..5b75e6003458 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -81,7 +81,8 @@ obj-$(CONFIG_FAIL_FUNCTION) += fail_function.o
obj-$(CONFIG_KGDB) += debug/
obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
obj-$(CONFIG_LOCKUP_DETECTOR) += watchdog.o
-obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_hld.o
+obj-$(CONFIG_HARDLOCKUP_DETECTOR) += watchdog_hld.o
+obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_hld_perf.o
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 9724cd57307b..372db565b1b9 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -22,12 +22,8 @@

static DEFINE_PER_CPU(bool, hard_watchdog_warn);
static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
-static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
-static DEFINE_PER_CPU(struct perf_event *, dead_event);
-static struct cpumask dead_events_mask;

static unsigned long hardlockup_allcpu_dumped;
-static atomic_t watchdog_cpus = ATOMIC_INIT(0);

notrace void arch_touch_nmi_watchdog(void)
{
@@ -98,14 +94,6 @@ static inline bool watchdog_check_timestamp(void)
}
#endif

-static struct perf_event_attr wd_hw_attr = {
- .type = PERF_TYPE_HARDWARE,
- .config = PERF_COUNT_HW_CPU_CYCLES,
- .size = sizeof(struct perf_event_attr),
- .pinned = 1,
- .disabled = 1,
-};
-
void inspect_for_hardlockups(struct pt_regs *regs)
{
if (__this_cpu_read(watchdog_nmi_touch) == true) {
@@ -156,144 +144,3 @@ void inspect_for_hardlockups(struct pt_regs *regs)
return;
}

-/* Callback function for perf event subsystem */
-static void watchdog_overflow_callback(struct perf_event *event,
- struct perf_sample_data *data,
- struct pt_regs *regs)
-{
- /* Ensure the watchdog never gets throttled */
- event->hw.interrupts = 0;
- inspect_for_hardlockups(regs);
-}
-
-static int hardlockup_detector_event_create(void)
-{
- unsigned int cpu = smp_processor_id();
- struct perf_event_attr *wd_attr;
- struct perf_event *evt;
-
- wd_attr = &wd_hw_attr;
- wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
-
- /* Try to register using hardware perf events */
- evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
- watchdog_overflow_callback, NULL);
- if (IS_ERR(evt)) {
- pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
- PTR_ERR(evt));
- return PTR_ERR(evt);
- }
- this_cpu_write(watchdog_ev, evt);
- return 0;
-}
-
-/**
- * hardlockup_detector_perf_enable - Enable the local event
- */
-void hardlockup_detector_perf_enable(void)
-{
- if (hardlockup_detector_event_create())
- return;
-
- /* use original value for check */
- if (!atomic_fetch_inc(&watchdog_cpus))
- pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
-
- perf_event_enable(this_cpu_read(watchdog_ev));
-}
-
-/**
- * hardlockup_detector_perf_disable - Disable the local event
- */
-void hardlockup_detector_perf_disable(void)
-{
- struct perf_event *event = this_cpu_read(watchdog_ev);
-
- if (event) {
- perf_event_disable(event);
- this_cpu_write(watchdog_ev, NULL);
- this_cpu_write(dead_event, event);
- cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
- atomic_dec(&watchdog_cpus);
- }
-}
-
-/**
- * hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them
- *
- * Called from lockup_detector_cleanup(). Serialized by the caller.
- */
-void hardlockup_detector_perf_cleanup(void)
-{
- int cpu;
-
- for_each_cpu(cpu, &dead_events_mask) {
- struct perf_event *event = per_cpu(dead_event, cpu);
-
- /*
- * Required because for_each_cpu() reports unconditionally
- * CPU0 as set on UP kernels. Sigh.
- */
- if (event)
- perf_event_release_kernel(event);
- per_cpu(dead_event, cpu) = NULL;
- }
- cpumask_clear(&dead_events_mask);
-}
-
-/**
- * hardlockup_detector_perf_stop - Globally stop watchdog events
- *
- * Special interface for x86 to handle the perf HT bug.
- */
-void __init hardlockup_detector_perf_stop(void)
-{
- int cpu;
-
- lockdep_assert_cpus_held();
-
- for_each_online_cpu(cpu) {
- struct perf_event *event = per_cpu(watchdog_ev, cpu);
-
- if (event)
- perf_event_disable(event);
- }
-}
-
-/**
- * hardlockup_detector_perf_restart - Globally restart watchdog events
- *
- * Special interface for x86 to handle the perf HT bug.
- */
-void __init hardlockup_detector_perf_restart(void)
-{
- int cpu;
-
- lockdep_assert_cpus_held();
-
- if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
- return;
-
- for_each_online_cpu(cpu) {
- struct perf_event *event = per_cpu(watchdog_ev, cpu);
-
- if (event)
- perf_event_enable(event);
- }
-}
-
-/**
- * hardlockup_detector_perf_init - Probe whether NMI event is available at all
- */
-int __init hardlockup_detector_perf_init(void)
-{
- int ret = hardlockup_detector_event_create();
-
- if (ret) {
- pr_info("Perf NMI watchdog permanently disabled\n");
- } else {
- perf_event_release_kernel(this_cpu_read(watchdog_ev));
- this_cpu_write(watchdog_ev, NULL);
- }
- return ret;
-}
diff --git a/kernel/watchdog_hld_perf.c b/kernel/watchdog_hld_perf.c
new file mode 100644
index 000000000000..1d06ec5a8e42
--- /dev/null
+++ b/kernel/watchdog_hld_perf.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Detect hard lockups on a system
+ *
+ * Copyright (C) Intel Corporation 2019
+ *
+ * Note: All of this code comes from the original perf-specific hardlockup
+ * detector.
+ */
+
+#define pr_fmt(fmt) "NMI perf watchdog: " fmt
+
+#include <linux/nmi.h>
+#include <linux/atomic.h>
+#include <linux/module.h>
+#include <linux/sched/debug.h>
+#include <linux/perf_event.h>
+#include <asm/irq_regs.h>
+
+static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
+static DEFINE_PER_CPU(struct perf_event *, dead_event);
+static struct cpumask dead_events_mask;
+
+static atomic_t watchdog_cpus = ATOMIC_INIT(0);
+
+static struct perf_event_attr wd_hw_attr = {
+ .type = PERF_TYPE_HARDWARE,
+ .config = PERF_COUNT_HW_CPU_CYCLES,
+ .size = sizeof(struct perf_event_attr),
+ .pinned = 1,
+ .disabled = 1,
+};
+
+/* Callback function for perf event subsystem */
+static void watchdog_overflow_callback(struct perf_event *event,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
+{
+ /* Ensure the watchdog never gets throttled */
+ event->hw.interrupts = 0;
+ inspect_for_hardlockups(regs);
+}
+
+static int hardlockup_detector_event_create(void)
+{
+ unsigned int cpu = smp_processor_id();
+ struct perf_event_attr *wd_attr;
+ struct perf_event *evt;
+
+ wd_attr = &wd_hw_attr;
+ wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
+
+ /* Try to register using hardware perf events */
+ evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
+ watchdog_overflow_callback, NULL);
+ if (IS_ERR(evt)) {
+ pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
+ PTR_ERR(evt));
+ return PTR_ERR(evt);
+ }
+ this_cpu_write(watchdog_ev, evt);
+ return 0;
+}
+
+/**
+ * hardlockup_detector_perf_enable - Enable the local event
+ */
+void hardlockup_detector_perf_enable(void)
+{
+ if (hardlockup_detector_event_create())
+ return;
+
+ /* use original value for check */
+ if (!atomic_fetch_inc(&watchdog_cpus))
+ pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
+
+ perf_event_enable(this_cpu_read(watchdog_ev));
+}
+
+/**
+ * hardlockup_detector_perf_disable - Disable the local event
+ */
+void hardlockup_detector_perf_disable(void)
+{
+ struct perf_event *event = this_cpu_read(watchdog_ev);
+
+ if (event) {
+ perf_event_disable(event);
+ this_cpu_write(watchdog_ev, NULL);
+ this_cpu_write(dead_event, event);
+ cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
+ atomic_dec(&watchdog_cpus);
+ }
+}
+
+/**
+ * hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them
+ *
+ * Called from lockup_detector_cleanup(). Serialized by the caller.
+ */
+void hardlockup_detector_perf_cleanup(void)
+{
+ int cpu;
+
+ for_each_cpu(cpu, &dead_events_mask) {
+ struct perf_event *event = per_cpu(dead_event, cpu);
+
+ /*
+ * Required because for_each_cpu() reports unconditionally
+ * CPU0 as set on UP kernels. Sigh.
+ */
+ if (event)
+ perf_event_release_kernel(event);
+ per_cpu(dead_event, cpu) = NULL;
+ }
+ cpumask_clear(&dead_events_mask);
+}
+
+/**
+ * hardlockup_detector_perf_stop - Globally stop watchdog events
+ *
+ * Special interface for x86 to handle the perf HT bug.
+ */
+void __init hardlockup_detector_perf_stop(void)
+{
+ int cpu;
+
+ lockdep_assert_cpus_held();
+
+ for_each_online_cpu(cpu) {
+ struct perf_event *event = per_cpu(watchdog_ev, cpu);
+
+ if (event)
+ perf_event_disable(event);
+ }
+}
+
+/**
+ * hardlockup_detector_perf_restart - Globally restart watchdog events
+ *
+ * Special interface for x86 to handle the perf HT bug.
+ */
+void __init hardlockup_detector_perf_restart(void)
+{
+ int cpu;
+
+ lockdep_assert_cpus_held();
+
+ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+ return;
+
+ for_each_online_cpu(cpu) {
+ struct perf_event *event = per_cpu(watchdog_ev, cpu);
+
+ if (event)
+ perf_event_enable(event);
+ }
+}
+
+/**
+ * hardlockup_detector_perf_init - Probe whether NMI event is available at all
+ */
+int __init hardlockup_detector_perf_init(void)
+{
+ int ret = hardlockup_detector_event_create();
+
+ if (ret) {
+ pr_info("Perf NMI watchdog permanently disabled\n");
+ } else {
+ perf_event_release_kernel(this_cpu_read(watchdog_ev));
+ this_cpu_write(watchdog_ev, NULL);
+ }
+ return ret;
+}
+
--
2.17.1
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