Implement g_call_me() as a way for geom methods to schedule operations

to be performed in the event-thread.

To do this, we need to lock the eventlist with g_eventlock (nee g_doorlock),
since g_call_me() being called from the UP/DOWN paths will not be able to
aquire g_topology_lock.

This also means that for now these events are not referenced on any
particular consumer/provider/geom.

For UP/DOWN path use, this will not become a problem since the access()
function will make sure we drain any bio's before we dismantle.

Sponsored by:   DARPA & NAI Labs.

3 files changed, 36 insertions, 1 deletions

diff --git a/sys/geom/geom.h b/sys/geom/geom.h
index df7ecb56ae13..018c8f6075b6 100644
--- a/sys/geom/geom.h
+++ b/sys/geom/geom.h
@@ -180,9 +180,11 @@ void g_trace(int level, char *, ...);
 
 
 /* geom_event.c */
+typedef void g_call_me_t(void *);
+int g_call_me(g_call_me_t *func, void *arg);
 void g_orphan_provider(struct g_provider *pp, int error);
-void g_waitidle(void);
 void g_silence(void);
+void g_waitidle(void);
 
 /* geom_subr.c */
 int g_access_abs(struct g_consumer *cp, int read, int write, int exclusive);
diff --git a/sys/geom/geom_event.c b/sys/geom/geom_event.c
index c6c7c9a55ea9..41884056a4ab 100644
--- a/sys/geom/geom_event.c
+++ b/sys/geom/geom_event.c
@@ -151,8 +151,13 @@ g_do_event(struct g_event *ep)
 	    ep, ep->event, ep->class, ep->geom, ep->provider, ep->consumer);
 	g_topology_assert();
 	switch (ep->event) {
+	case EV_CALL_ME:
+		ep->func(ep->arg);
+		break;	
 	case EV_NEW_CLASS:
 		mp2 = ep->class;
+		if (g_shutdown)
+			break;
 		if (mp2->taste == NULL)
 			break;
 		if (g_shutdown)
@@ -226,12 +231,15 @@ one_event(void)
 			break;
 		g_orphan_register(pp);
 	}
+	mtx_lock(&g_eventlock);
 	ep = TAILQ_FIRST(&g_events);
 	if (ep == NULL) {
+		mtx_unlock(&g_eventlock);
 		g_topology_unlock();
 		return (0);
 	}
 	TAILQ_REMOVE(&g_events, ep, events);
+	mtx_unlock(&g_eventlock);
 	if (ep->class != NULL)
 		ep->class->event = NULL;
 	if (ep->geom != NULL)
@@ -288,9 +296,31 @@ g_post_event(enum g_events ev, struct g_class *mp, struct g_geom *gp, struct g_p
 		KASSERT(cp->event == NULL, ("Double event on consumer"));
 		cp->event = ep;
 	}
+	mtx_lock(&g_eventlock);
 	g_pending_events++;
 	TAILQ_INSERT_TAIL(&g_events, ep, events);
+	mtx_unlock(&g_eventlock);
+	wakeup(&g_wait_event);
+}
+
+int
+g_call_me(g_call_me_t *func, void *arg)
+{
+	struct g_event *ep;
+
+	g_trace(G_T_TOPOLOGY, "g_call_me(%p, %p", func, arg);
+	ep = g_malloc(sizeof *ep, M_NOWAIT | M_ZERO);
+	if (ep == NULL)
+		return (ENOMEM);
+	ep->event = EV_CALL_ME;
+	ep->func = func;
+	ep->arg = arg;
+	mtx_lock(&g_eventlock);
+	g_pending_events++;
+	TAILQ_INSERT_TAIL(&g_events, ep, events);
+	mtx_unlock(&g_eventlock);
 	wakeup(&g_wait_event);
+	return (0);
 }
 
 #ifdef _KERNEL
diff --git a/sys/geom/geom_int.h b/sys/geom/geom_int.h
index b7a5ad6f7de4..33fd6756c25e 100644
--- a/sys/geom/geom_int.h
+++ b/sys/geom/geom_int.h
@@ -51,6 +51,7 @@ enum g_events {
 	EV_NEW_CLASS,		/* class */
 	EV_NEW_PROVIDER,	/* provider */
 	EV_SPOILED,		/* provider, consumer */
+	EV_CALL_ME,		/* func, arg */
 	EV_LAST
 };
 
@@ -61,6 +62,8 @@ struct g_event {
 	struct g_geom		*geom;
 	struct g_provider	*provider;
 	struct g_consumer	*consumer;
+	void			*arg;
+	g_call_me_t		*func;
 };
 
 /* geom_dump.c */