Author: kib
Date: Wed Aug 3 07:11:19 2016
New Revision: 303703
URL: https://svnweb.freebsd.org/changeset/base/303703
Log:
Explain why swapgeom_close_ev() is delegated.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Modified:
head/sys/vm/swap_pager.c
Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c Wed Aug 3 07:10:09 2016 (r303702)
+++ head/sys/vm/swap_pager.c Wed Aug 3 07:11:19 2016 (r303703)
@@ -2431,8 +2431,9 @@ swapgeom_acquire(struct g_consumer *cp)
}
/*
- * Remove a reference from the g_consumer. Post a close event if
- * all references go away.
+ * Remove a reference from the g_consumer. Post a close event if all
+ * references go away, since the function might be called from the
+ * biodone context.
*/
static void
swapgeom_release(struct g_consumer *cp, struct swdevt *sp)
@@ -2555,7 +2556,12 @@ swapgeom_close(struct thread *td, struct
cp = sw->sw_id;
sw->sw_id = NULL;
mtx_unlock(&sw_dev_mtx);
- /* XXX: direct call when Giant untangled */
+
+ /*
+ * swapgeom_close() may be called from the biodone context,
+ * where we cannot perform topology changes. Delegate the
+ * work to the events thread.
+ */
if (cp != NULL)
g_waitfor_event(swapgeom_close_ev, cp, M_WAITOK, NULL);
}
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