linux-kernel - [PATCH] perf_counter: Always return the parent counter id to userspace

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Message-ID: <20090720103825.GA9029@kryten>
Date:	Mon, 20 Jul 2009 20:38:25 +1000
From:	Anton Blanchard <anton@...ba.org>
To:	a.p.zijlstra@...llo.nl, mingo@...e.hu, paulus@...ba.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] perf_counter: Always return the parent counter id to
	userspace


When inheriting counters new tasks get new counter ids. Since
userspace only knows about the parent ids we need to return them
and not the actual ids.

Signed-off-by: Anton Blanchard <anton@...ba.org>
---

Index: linux.trees.git/kernel/perf_counter.c
===================================================================
--- linux.trees.git.orig/kernel/perf_counter.c	2009-07-20 20:17:44.000000000 +1000
+++ linux.trees.git/kernel/perf_counter.c	2009-07-20 20:36:13.000000000 +1000
@@ -154,6 +154,20 @@
 	}
 }
 
+/* 
+ * If we inherit counters we want to return the parent counter id 
+ * to userspace.
+ */
+static u64 primary_counter_id(struct perf_counter *counter)
+{
+	u64 id = counter->id;
+
+	if (counter->parent)
+		id = counter->parent->id;
+
+	return id;
+}
+
 /*
  * Get the perf_counter_context for a task and lock it.
  * This has to cope with with the fact that until it is locked,
@@ -1705,7 +1719,7 @@
 		values[n++] = counter->total_time_running +
 			atomic64_read(&counter->child_total_time_running);
 	if (counter->attr.read_format & PERF_FORMAT_ID)
-		values[n++] = counter->id;
+		values[n++] = primary_counter_id(counter);
 	mutex_unlock(&counter->child_mutex);
 
 	if (count < n * sizeof(u64))
@@ -2548,7 +2562,7 @@
 		lost_event.header.type = PERF_EVENT_LOST;
 		lost_event.header.misc = 0;
 		lost_event.header.size = sizeof(lost_event);
-		lost_event.id          = counter->id;
+		lost_event.id          = primary_counter_id(counter);
 		lost_event.lost        = atomic_xchg(&data->lost, 0);
 
 		perf_output_put(handle, lost_event);
@@ -2704,8 +2718,10 @@
 	if (sample_type & PERF_SAMPLE_ADDR)
 		perf_output_put(&handle, data->addr);
 
-	if (sample_type & PERF_SAMPLE_ID)
-		perf_output_put(&handle, counter->id);
+	if (sample_type & PERF_SAMPLE_ID) {
+		u64 id = primary_counter_id(counter);
+		perf_output_put(&handle, id);
+	}
 
 	if (sample_type & PERF_SAMPLE_CPU)
 		perf_output_put(&handle, cpu_entry);
@@ -2727,7 +2743,7 @@
 			if (sub != counter)
 				sub->pmu->read(sub);
 
-			group_entry.id = sub->id;
+			group_entry.id = primary_counter_id(sub);
 			group_entry.counter = atomic64_read(&sub->count);
 
 			perf_output_put(&handle, group_entry);
@@ -2790,11 +2806,7 @@
 		u64 id;
 
 		event.header.size += sizeof(u64);
-		if (counter->parent)
-			id = counter->parent->id;
-		else
-			id = counter->id;
-
+		id = primary_counter_id(counter);
 		event.format[i++] = id;
 	}
 
@@ -3209,7 +3221,7 @@
 			.size = sizeof(event),
 		},
 		.time = sched_clock(),
-		.id = counter->id,
+		.id = primary_counter_id(counter),
 		.period = period,
 	};
 
@@ -3241,7 +3253,7 @@
 			.size = sizeof(throttle_event),
 		},
 		.time	= sched_clock(),
-		.id	= counter->id,
+		.id	= primary_counter_id(counter),
 	};
 
 	ret = perf_output_begin(&handle, counter, sizeof(throttle_event), 1, 0);
--
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