From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Tue, 8 Nov 2011 08:29:51 +0000 (-0800)
Subject: kernel - Add callout_stop_sync()
X-Git-Tag: v3.0.0~706
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/c5b9d2a5dc3047fc20e0a12e1a1de7a4aa424db2

kernel - Add callout_stop_sync()

* Add a synchronous version of callout_stop() which ensure that the
  callout function has completed operation (if it was running) before
  returning.
---

diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index 5ca8f2df73..8eed720f19 100644
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -399,6 +399,9 @@ callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
  *
  * WARNING! This function can return while it's c_func is still running
  *	    in the callout thread, a secondary check may be needed.
+ *	    Use callout_stop_sync() to wait for any callout function to
+ *	    complete before returning, being sure that no deadlock is
+ *	    possible if you do.
  */
 int
 callout_stop(struct callout *c)
@@ -487,6 +490,30 @@ callout_stop(struct callout *c)
 	return (1);
 }
 
+/*
+ * Issue a callout_stop() and ensure that any callout race completes
+ * before returning.  Does NOT de-initialized the callout.
+ */
+void
+callout_stop_sync(struct callout *c)
+{
+	softclock_pcpu_t sc;
+
+	if (c->c_flags & CALLOUT_DID_INIT) {
+		callout_stop(c);
+#ifdef SMP
+		sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
+#else
+		sc = &softclock_pcpu_ary[0];
+#endif
+		if (sc->running == c) {
+			while (sc->running == c)
+				tsleep(&sc->running, 0, "crace", 1);
+		}
+		KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
+	}
+}
+
 /*
  * Terminate a callout
  *
diff --git a/sys/sys/callout.h b/sys/sys/callout.h
index b279a5fede..a74d1ca9f4 100644
--- a/sys/sys/callout.h
+++ b/sys/sys/callout.h
@@ -94,6 +94,7 @@ void	callout_init (struct callout *);
 void	callout_init_mp (struct callout *);
 void	callout_reset (struct callout *, int, void (*)(void *), void *);
 int	callout_stop (struct callout *);
+void	callout_stop_sync (struct callout *);
 void	callout_terminate (struct callout *);
 
 #endif