perf_counter: theres more to overflow than writing events

Prepare for more generic overflow handling. The new perf_counter_overflow()
method will handle the generic bits of the counter overflow, and can return
a !0 return value, in which case the counter should be (soft) disabled, so
that it won't count until it's properly disabled.

XXX: do powerpc and swcounter

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094517.812109629@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 23 insertions, 6 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 0a2ade2e4f11..195e976eb07d 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1800,8 +1800,8 @@ static void perf_output_end(struct perf_output_handle *handle)
         rcu_read_unlock();
 }
 
-void perf_counter_output(struct perf_counter *counter,
-                         int nmi, struct pt_regs *regs)
+static void perf_counter_output(struct perf_counter *counter,
+                                int nmi, struct pt_regs *regs)
 {
         int ret;
         u64 record_type = counter->hw_event.record_type;
@@ -2034,6 +2034,17 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
 }
 
 /*
+ * Generic counter overflow handling.
+ */
+
+int perf_counter_overflow(struct perf_counter *counter,
+                          int nmi, struct pt_regs *regs)
+{
+        perf_counter_output(counter, nmi, regs);
+        return 0;
+}
+
+/*
  * Generic software counter infrastructure
  */
 
@@ -2077,6 +2088,7 @@ static void perf_swcounter_set_period(struct perf_counter *counter)
 
 static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
 {
+        enum hrtimer_restart ret = HRTIMER_RESTART;
         struct perf_counter *counter;
         struct pt_regs *regs;
 
@@ -2092,12 +2104,14 @@ static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
                         !counter->hw_event.exclude_user)
                 regs = task_pt_regs(current);
 
-        if (regs)
-                perf_counter_output(counter, 0, regs);
+        if (regs) {
+                if (perf_counter_overflow(counter, 0, regs))
+                        ret = HRTIMER_NORESTART;
+        }
 
         hrtimer_forward_now(hrtimer, ns_to_ktime(counter->hw.irq_period));
 
-        return HRTIMER_RESTART;
+        return ret;
 }
 
 static void perf_swcounter_overflow(struct perf_counter *counter,
@@ -2105,7 +2119,10 @@ static void perf_swcounter_overflow(struct perf_counter *counter,
 {
         perf_swcounter_update(counter);
         perf_swcounter_set_period(counter);
-        perf_counter_output(counter, nmi, regs);
+        if (perf_counter_overflow(counter, nmi, regs))
+                /* soft-disable the counter */
+                ;
+
 }
 
 static int perf_swcounter_match(struct perf_counter *counter,