On Wed, 2010-12-08 at 09:01 -0500, Don Zickus wrote:
Something like so then?
---
Subject: perf: Stop all counters on reboot
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed Dec 08 15:29:02 CET 2010
Use the reboot notifier to detach all running counters on reboot, this
solves a problem with kexec where the new kernel doesn't expect
running counters (rightly so).
It will however decrease the coverage of the NMI watchdog. Making a
kexec specific reboot notifier callback would be best, however that
would require touching all notifier callback handlers as they are not
properly structured to deal with new state.
As a compromise, place the perf reboot notifier at the very last
position in the list.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -21,6 +21,7 @@
#include <linux/dcache.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
+#include <linux/reboot.h>
#include <linux/vmstat.h>
#include <linux/vmalloc.h>
#include <linux/hardirq.h>
@@ -6329,7 +6330,7 @@ static void __cpuinit perf_event_init_cp
mutex_unlock(&swhash->hlist_mutex);
}
-#ifdef CONFIG_HOTPLUG_CPU
+#if defined CONFIG_HOTPLUG_CPU || defined CONFIG_KEXEC
static void perf_pmu_rotate_stop(struct pmu *pmu)
{
struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
@@ -6383,6 +6384,26 @@ static void perf_event_exit_cpu(int cpu)
static inline void perf_event_exit_cpu(int cpu) { }
#endif
+static int
+perf_reboot(struct notifier_block *notifier, unsigned long val, void *v)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu)
+ perf_event_exit_cpu(cpu);
+
+ return NOTIFY_OK;
+}
+
+/*
+ * Run the perf reboot notifier at the very last possible moment so that
+ * the generic watchdog code runs as long as possible.
+ */
+static struct notifier_block perf_reboot_notifier = {
+ .notifier_call = perf_reboot,
+ .priority = INT_MIN,
+};
+
static int __cpuinit
perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
{
@@ -6418,6 +6439,7 @@ void __init perf_event_init(void)
perf_pmu_register(&perf_task_clock);
perf_tp_register();
perf_cpu_notifier(perf_cpu_notify);
+ register_reboot_notifier(&perf_reboot_notifier);
ret = init_hw_breakpoint();
WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
--
