Markers fixes

Index: linux-2.6-lttng/kernel/marker.c
===================================================================
@@ -60,6 +60,9 @@ struct marker_entry {
 	struct marker_probe_closure single;
 	struct marker_probe_closure *multi;
 	int refcount;	/* Number of times armed. 0 if disarmed. */
+	struct rcu_head rcu;
+	void *oldptr;
+	unsigned char rcu_pending:1;
 	unsigned char ptype:1;
 	char name[0];	/* Contains name'\0'format'\0' */
 };

@@ -196,6 +199,16 @@ void marker_probe_cb_noarg(const struct 
 }
 EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
 
+static void free_old_closure(struct rcu_head *head)
+{
+	struct marker_entry *entry = container_of(head,
+		struct marker_entry, rcu);
+	kfree(entry->oldptr);
+	/* Make sure we free the data before setting the pending flag to 0 */
+	smp_wmb();
+	entry->rcu_pending = 0;
+}
+
 static void debug_print_probes(struct marker_entry *entry)
 {
 	int i;

@@ -404,6 +417,7 @@ static struct marker_entry *add_marker(c
 	e->multi = NULL;
 	e->ptype = 0;
 	e->refcount = 0;
+	e->rcu_pending = 0;
 	hlist_add_head(&e->hlist, head);
 	return e;
 }

@@ -433,6 +447,9 @@ static int remove_marker(const char *nam
 	if (e->single.func != __mark_empty_function)
 		return -EBUSY;
 	hlist_del(&e->hlist);
+	/* Make sure the call_rcu has been executed */
+	if (e->rcu_pending)
+		rcu_barrier_sched();
 	kfree(e);
 	return 0;
 }

@@ -462,8 +479,12 @@ static int marker_set_format(struct mark
 	e->multi = (*entry)->multi;
 	e->ptype = (*entry)->ptype;
 	e->refcount = (*entry)->refcount;
+	e->rcu_pending = 0;
 	hlist_add_before(&e->hlist, &(*entry)->hlist);
 	hlist_del(&(*entry)->hlist);
+	/* Make sure the call_rcu has been executed */
+	if ((*entry)->rcu_pending)
+		rcu_barrier_sched();
 	kfree(*entry);
 	*entry = e;
 	trace_mark(core_marker_format, "name %s format %s",

@@ -637,6 +658,12 @@ int marker_probe_register(const char *na
 			goto end;
 		}
 	}
+	/*
+	 * If we detect that a call_rcu is pending for this marker,
+	 * make sure it's executed now.
+	 */
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
 	old = marker_entry_add_probe(entry, probe, probe_private);
 	if (IS_ERR(old)) {
 		ret = PTR_ERR(old);

@@ -644,11 +671,16 @@ int marker_probe_register(const char *na
 	}
 	mutex_unlock(&markers_mutex);
 	marker_update_probes();		/* may update entry */
-	synchronize_sched();
-	kfree(old);
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
 	WARN_ON(!entry);
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu_sched(&entry->rcu, free_old_closure);
 end:
 	mutex_unlock(&markers_mutex);
 	return ret;

@@ -678,15 +710,22 @@ int marker_probe_unregister(const char *
 	entry = get_marker(name);
 	if (!entry)
 		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
 	old = marker_entry_remove_probe(entry, probe, probe_private);
 	mutex_unlock(&markers_mutex);
 	marker_update_probes();		/* may update entry */
-	synchronize_sched();
-	kfree(old);
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
 	if (!entry)
 		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu_sched(&entry->rcu, free_old_closure);
 	remove_marker(name);	/* Ignore busy error message */
 	ret = 0;
 end:

@@ -752,14 +791,21 @@ int marker_probe_unregister_private_data
 		ret = -ENOENT;
 		goto end;
 	}
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
 	old = marker_entry_remove_probe(entry, NULL, probe_private);
 	mutex_unlock(&markers_mutex);
 	marker_update_probes();		/* may update entry */
-	synchronize_sched();
-	kfree(old);
 	mutex_lock(&markers_mutex);
 	entry = get_marker_from_private_data(probe, probe_private);
 	WARN_ON(!entry);
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu_sched(&entry->rcu, free_old_closure);
 	remove_marker(entry->name);	/* Ignore busy error message */
 end:
 	mutex_unlock(&markers_mutex);

Index: linux-2.6-lttng/include/linux/marker.h
===================================================================
@@ -142,4 +142,11 @@ extern int marker_probe_unregister_priva
 extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
 	int num);
 
+/*
+ * marker_synchronize_unregister must be called between the last marker probe
+ * unregistration and the end of module exit to make sure there is no caller
+ * executing a probe when it is freed.
+ */
+#define marker_synchronize_unregister() synchronize_sched()
+
 #endif

Index: linux-2.6-lttng/samples/markers/probe-example.c
===================================================================
@@ -81,6 +81,7 @@ static void __exit probe_fini(void)
 			probe_array[i].probe_func, &probe_array[i]);
 	printk(KERN_INFO "Number of event b : %u\n",
 			atomic_read(&eventb_count));
+	marker_synchronize_unregister();
 }
 
 module_init(probe_init);

Index: linux-2.6-lttng/arch/powerpc/platforms/cell/spufs/sputrace.c
===================================================================
@@ -233,6 +233,7 @@ static void __exit sputrace_exit(void)
 
 	remove_proc_entry("sputrace", NULL);
 	kfree(sputrace_log);
+	marker_synchronize_unregister();
 }
 
 module_init(sputrace_init);