oprofile: convert oprofile from timer_hook to hrtimer

Oprofile is currently broken on systems running with NOHZ enabled.
A maximum of 1 tick is accounted via the timer_hook if a cpu sleeps
for a longer period of time. This does bad things to the percentages
in the profiler output. To solve this problem convert oprofile to
use a restarting hrtimer instead of the timer_hook.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>

3 files changed, 79 insertions, 14 deletions

diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
index dc8a0428260d..b336cd9ee7a1 100644
--- a/drivers/oprofile/oprof.c
+++ b/drivers/oprofile/oprof.c
@@ -253,22 +253,26 @@ static int __init oprofile_init(void)
         int err;
 
         err = oprofile_arch_init(&oprofile_ops);
-
         if (err < 0 || timer) {
                 printk(KERN_INFO "oprofile: using timer interrupt.\n");
-                oprofile_timer_init(&oprofile_ops);
+                err = oprofile_timer_init(&oprofile_ops);
+                if (err)
+                        goto out_arch;
         }
-
         err = oprofilefs_register();
         if (err)
-                oprofile_arch_exit();
+                goto out_arch;
+        return 0;
 
+out_arch:
+        oprofile_arch_exit();
         return err;
 }
 
 
 static void __exit oprofile_exit(void)
 {
+        oprofile_timer_exit();
         oprofilefs_unregister();
         oprofile_arch_exit();
 }
diff --git a/drivers/oprofile/oprof.h b/drivers/oprofile/oprof.h
index cb92f5c98c1a..47e12cb4ee8b 100644
--- a/drivers/oprofile/oprof.h
+++ b/drivers/oprofile/oprof.h
@@ -34,7 +34,8 @@ struct super_block;
 struct dentry;
 
 void oprofile_create_files(struct super_block *sb, struct dentry *root);
-void oprofile_timer_init(struct oprofile_operations *ops);
+int oprofile_timer_init(struct oprofile_operations *ops);
+void oprofile_timer_exit(void);
 
 int oprofile_set_backtrace(unsigned long depth);
 int oprofile_set_timeout(unsigned long time);
diff --git a/drivers/oprofile/timer_int.c b/drivers/oprofile/timer_int.c
index 333f915568c7..dc0ae4d14dff 100644
--- a/drivers/oprofile/timer_int.c
+++ b/drivers/oprofile/timer_int.c
@@ -13,34 +13,94 @@
 #include <linux/oprofile.h>
 #include <linux/profile.h>
 #include <linux/init.h>
+#include <linux/cpu.h>
+#include <linux/hrtimer.h>
+#include <asm/irq_regs.h>
 #include <asm/ptrace.h>
 
 #include "oprof.h"
 
-static int timer_notify(struct pt_regs *regs)
+static DEFINE_PER_CPU(struct hrtimer, oprofile_hrtimer);
+
+static enum hrtimer_restart oprofile_hrtimer_notify(struct hrtimer *hrtimer)
+{
+        oprofile_add_sample(get_irq_regs(), 0);
+        hrtimer_forward_now(hrtimer, ns_to_ktime(TICK_NSEC));
+        return HRTIMER_RESTART;
+}
+
+static void __oprofile_hrtimer_start(void *unused)
+{
+        struct hrtimer *hrtimer = &__get_cpu_var(oprofile_hrtimer);
+
+        hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hrtimer->function = oprofile_hrtimer_notify;
+
+        hrtimer_start(hrtimer, ns_to_ktime(TICK_NSEC),
+                      HRTIMER_MODE_REL_PINNED);
+}
+
+static int oprofile_hrtimer_start(void)
 {
-        oprofile_add_sample(regs, 0);
+        on_each_cpu(__oprofile_hrtimer_start, NULL, 1);
         return 0;
 }
 
-static int timer_start(void)
+static void __oprofile_hrtimer_stop(int cpu)
 {
-        return register_timer_hook(timer_notify);
+        struct hrtimer *hrtimer = &per_cpu(oprofile_hrtimer, cpu);
+
+        hrtimer_cancel(hrtimer);
 }
 
+static void oprofile_hrtimer_stop(void)
+{
+        int cpu;
+
+        for_each_online_cpu(cpu)
+                __oprofile_hrtimer_stop(cpu);
+}
 
-static void timer_stop(void)
+static int __cpuinit oprofile_cpu_notify(struct notifier_block *self,
+                                         unsigned long action, void *hcpu)
 {
-        unregister_timer_hook(timer_notify);
+        long cpu = (long) hcpu;
+
+        switch (action) {
+        case CPU_ONLINE:
+        case CPU_ONLINE_FROZEN:
+                smp_call_function_single(cpu, __oprofile_hrtimer_start,
+                                         NULL, 1);
+                break;
+        case CPU_DEAD:
+        case CPU_DEAD_FROZEN:
+                __oprofile_hrtimer_stop(cpu);
+                break;
+        }
+        return NOTIFY_OK;
 }
 
+static struct notifier_block __refdata oprofile_cpu_notifier = {
+        .notifier_call = oprofile_cpu_notify,
+};
 
-void __init oprofile_timer_init(struct oprofile_operations *ops)
+int __init oprofile_timer_init(struct oprofile_operations *ops)
 {
+        int rc;
+
+        rc = register_hotcpu_notifier(&oprofile_cpu_notifier);
+        if (rc)
+                return rc;
         ops->create_files = NULL;
         ops->setup = NULL;
         ops->shutdown = NULL;
-        ops->start = timer_start;
-        ops->stop = timer_stop;
+        ops->start = oprofile_hrtimer_start;
+        ops->stop = oprofile_hrtimer_stop;
         ops->cpu_type = "timer";
+        return 0;
+}
+
+void __exit oprofile_timer_exit(void)
+{
+        unregister_hotcpu_notifier(&oprofile_cpu_notifier);
 }