commit e98effc7019769cda1b223e50a735b8b8f84e8c1
Author: Ryota Ozaki <ozaki-r@iij.ad.jp>
Date:   Mon Nov 17 17:33:43 2014 +0900

    Pull workqueue_destroy out of sme->sme_mtx

diff --git a/sys/dev/sysmon/sysmon_envsys.c b/sys/dev/sysmon/sysmon_envsys.c
index 57967ea..2832ce7 100644
--- a/sys/dev/sysmon/sysmon_envsys.c
+++ b/sys/dev/sysmon/sysmon_envsys.c
@@ -579,6 +579,7 @@ sysmon_envsys_sensor_detach(struct sysmon_envsys *sme, envsys_data_t *edata)
 {
 	envsys_data_t *oedata;
 	bool found = false;
+	bool destroy = false;
 
 	KASSERT(sme != NULL || edata != NULL);
 
@@ -604,11 +605,18 @@ sysmon_envsys_sensor_detach(struct sysmon_envsys *sme, envsys_data_t *edata)
 	 * remove it, unhook from rnd(4), and decrement the sensors count.
 	 */
 	sme_event_unregister_sensor(sme, edata);
+	if (LIST_EMPTY(&sme->sme_events_list)) {
+		sme_events_halt_callout(sme);
+		destroy = true;
+	}
 	TAILQ_REMOVE(&sme->sme_sensors_list, edata, sensors_head);
 	sme->sme_nsensors--;
 	sysmon_envsys_release(sme, true);
 	mutex_exit(&sme->sme_mtx);
 
+	if (destroy)
+		sme_events_destroy(sme);
+
 	return 0;
 }
 
@@ -918,10 +926,6 @@ sysmon_envsys_unregister(struct sysmon_envsys *sme)
 	KASSERT(sme != NULL);
 
 	/*
-	 * Unregister all events associated with device.
-	 */
-	sme_event_unregister_all(sme);
-	/*
 	 * Decrement global sensors counter and the first_sensor index
 	 * for remaining devices in the list (only used for compatibility
 	 * with previous API), and remove the device from the list.
@@ -936,6 +940,11 @@ sysmon_envsys_unregister(struct sysmon_envsys *sme)
 	mutex_exit(&sme_global_mtx);
 
 	/*
+	 * Unregister all events associated with device.
+	 */
+	sme_event_unregister_all(sme);
+
+	/*
 	 * Remove the device (and all its objects) from the global dictionary.
 	 */
 	array = prop_dictionary_get(sme_propd, sme->sme_name);
diff --git a/sys/dev/sysmon/sysmon_envsys_events.c b/sys/dev/sysmon/sysmon_envsys_events.c
index 38c5914..56409fa 100644
--- a/sys/dev/sysmon/sysmon_envsys_events.c
+++ b/sys/dev/sysmon/sysmon_envsys_events.c
@@ -345,6 +345,7 @@ sme_event_unregister_all(struct sysmon_envsys *sme)
 {
 	sme_event_t *see;
 	int evcounter = 0;
+	bool destroy = false;
 
 	KASSERT(sme != NULL);
 
@@ -374,10 +375,15 @@ sme_event_unregister_all(struct sysmon_envsys *sme)
 		}
 	}
 
-	if (LIST_EMPTY(&sme->sme_events_list))
-		if (sme->sme_flags & SME_CALLOUT_INITIALIZED)
-			sme_events_destroy(sme);
+	if (LIST_EMPTY(&sme->sme_events_list) &&
+	    sme->sme_flags & SME_CALLOUT_INITIALIZED) {
+		sme_events_halt_callout(sme);
+		destroy = true;
+	}
 	mutex_exit(&sme->sme_mtx);
+
+	if (destroy)
+		sme_events_destroy(sme);
 }
 
 /*
@@ -470,15 +476,6 @@ sme_remove_event(sme_event_t *see, struct sysmon_envsys *sme)
 	if (see->see_edata->flags & ENVSYS_FHAS_ENTROPY)
 		rnd_detach_source(&see->see_edata->rnd_src);
 	LIST_REMOVE(see, see_list);
-	/*
-	 * So the events list is empty, we'll do the following:
-	 *
-	 * 	- stop and destroy the callout.
-	 * 	- destroy the workqueue.
-	 */
-	if (LIST_EMPTY(&sme->sme_events_list))
-		sme_events_destroy(sme);
-
 	kmem_free(see, sizeof(*see));
 }
 
@@ -601,13 +598,12 @@ sme_schedule_callout(struct sysmon_envsys *sme)
 }
 
 /*
- * sme_events_destroy:
+ * sme_events_halt_callout:
  *
- * 	+ Destroys the event framework for this device: callout
- * 	  stopped, workqueue destroyed and callout mutex destroyed.
+ * 	+ Halt the callout of the event framework for this device.
  */
 void
-sme_events_destroy(struct sysmon_envsys *sme)
+sme_events_halt_callout(struct sysmon_envsys *sme)
 {
 	KASSERT(mutex_owned(&sme->sme_mtx));
 
@@ -618,9 +614,23 @@ sme_events_destroy(struct sysmon_envsys *sme)
 	sme->sme_flags &= ~SME_CALLOUT_INITIALIZED;
 
 	callout_halt(&sme->sme_callout, &sme->sme_mtx);
+}
+
+/*
+ * sme_events_destroy:
+ *
+ * 	+ Destroy the callout and the workqueue of the event framework
+ *	  for this device.
+ */
+void
+sme_events_destroy(struct sysmon_envsys *sme)
+{
+	KASSERT(!mutex_owned(&sme->sme_mtx));
+	KASSERT((sme->sme_flags & SME_CALLOUT_INITIALIZED) == 0);
+
 	callout_destroy(&sme->sme_callout);
-
 	workqueue_destroy(sme->sme_wq);
+
 	DPRINTF(("%s: events framework destroyed for '%s'\n",
 	    __func__, sme->sme_name));
 }
diff --git a/sys/dev/sysmon/sysmon_envsysvar.h b/sys/dev/sysmon/sysmon_envsysvar.h
index 52128f4..84b76d4 100644
--- a/sys/dev/sysmon/sysmon_envsysvar.h
+++ b/sys/dev/sysmon/sysmon_envsysvar.h
@@ -137,6 +137,7 @@ void	sme_event_unregister_all(struct sysmon_envsys *);
 void	sme_event_drvadd(void *);
 int	sme_events_init(struct sysmon_envsys *);
 void	sme_events_destroy(struct sysmon_envsys *);
+void	sme_events_halt_callout(struct sysmon_envsys *);
 void	sme_events_check(void *);
 void	sme_events_worker(struct work *, void *);
 void	sme_deliver_event(sme_event_t *);