From d04304d15550b2149a0bb9fccaa4ac50f29229c6 Mon Sep 17 00:00:00 2001
From: Gleb Smirnoff <glebius@FreeBSD.org>
Date: Thu, 8 Sep 2005 14:20:39 +0000
Subject: [PATCH] Make callout_reset() return a non-zero value if a pending
 callout was rescheduled. If there was no pending callout, then return 0.

Reviewed by:	iedowse, cperciva
---
 share/man/man9/timeout.9 | 12 +++++++-----
 sys/kern/kern_timeout.c  | 11 ++++++++---
 sys/sys/callout.h        |  2 +-
 3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/share/man/man9/timeout.9 b/share/man/man9/timeout.9
index 1589aed12e13..d683e32f69af 100644
--- a/share/man/man9/timeout.9
+++ b/share/man/man9/timeout.9
@@ -36,7 +36,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 6, 2005
+.Dd September 8, 2005
 .Dt TIMEOUT 9
 .Os
 .Sh NAME
@@ -77,7 +77,7 @@ struct callout_handle handle = CALLOUT_HANDLE_INITIALIZER(&handle)
 .Fn callout_stop "struct callout *c"
 .Ft int
 .Fn callout_drain "struct callout *c"
-.Ft void
+.Ft int
 .Fn callout_reset "struct callout *c" "int ticks" "timeout_t *func" "void *arg"
 .Ft int
 .Fn callout_pending "struct callout *c"
@@ -260,6 +260,9 @@ first performs the equivalent of
 to disestablish the callout, and then establishes a new callout in the
 same manner as
 .Fn timeout .
+If there was already a pending callout and it was rescheduled, then
+.Fn callout_reset
+will return a non-zero value.
 If the callout has an associated mutex, then that mutex must be
 held when this function is called.
 .Pp
@@ -346,6 +349,8 @@ before destroying the callout or its associated mutex.
 .It
 The return value from
 .Fn callout_stop
+and
+.Fn callout_reset
 indicates whether or not the callout was removed.
 If it is known that the callout was set and the callout function has
 not yet executed, then a return value of
@@ -366,9 +371,6 @@ if (sc->sc_flags & SCFLG_CALLOUT_RUNNING) {
 }
 .Ed
 .Pp
-Note that there is no equivalent mechanism to determine whether or not
-.Fn callout_reset
-stopped the callout.
 .It
 The
 .Fn callout_pending ,
diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index f2fafbb85dfa..8e6b183bb76f 100644
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -427,13 +427,14 @@ callout_handle_init(struct callout_handle *handle)
  * callout_pending() - returns truth if callout is still waiting for timeout
  * callout_deactivate() - marks the callout as having been serviced
  */
-void
+int
 callout_reset(c, to_ticks, ftn, arg)
 	struct	callout *c;
 	int	to_ticks;
 	void	(*ftn)(void *);
 	void	*arg;
 {
+	int cancelled = 0;
 
 #ifdef notyet /* Some callers of timeout() do not hold Giant. */
 	if (c->c_mtx != NULL)
@@ -448,14 +449,14 @@ callout_reset(c, to_ticks, ftn, arg)
 		 * can cancel the callout if it has not really started.
 		 */
 		if (c->c_mtx != NULL && !curr_cancelled)
-			curr_cancelled = 1;
+			cancelled = curr_cancelled = 1;
 		if (wakeup_needed) {
 			/*
 			 * Someone has called callout_drain to kill this
 			 * callout.  Don't reschedule.
 			 */
 			mtx_unlock_spin(&callout_lock);
-			return;
+			return (cancelled);
 		}
 	}
 	if (c->c_flags & CALLOUT_PENDING) {
@@ -465,6 +466,8 @@ callout_reset(c, to_ticks, ftn, arg)
 		TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c,
 		    c_links.tqe);
 
+		cancelled = 1;
+
 		/*
 		 * Part of the normal "stop a pending callout" process
 		 * is to clear the CALLOUT_ACTIVE and CALLOUT_PENDING
@@ -490,6 +493,8 @@ callout_reset(c, to_ticks, ftn, arg)
 	TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask], 
 			  c, c_links.tqe);
 	mtx_unlock_spin(&callout_lock);
+
+	return (cancelled);
 }
 
 int
diff --git a/sys/sys/callout.h b/sys/sys/callout.h
index cec907950d0b..a55456254640 100644
--- a/sys/sys/callout.h
+++ b/sys/sys/callout.h
@@ -81,7 +81,7 @@ extern struct mtx callout_lock;
 void	callout_init(struct callout *, int);
 void	callout_init_mtx(struct callout *, struct mtx *, int);
 #define	callout_pending(c)	((c)->c_flags & CALLOUT_PENDING)
-void	callout_reset(struct callout *, int, void (*)(void *), void *);
+int	callout_reset(struct callout *, int, void (*)(void *), void *);
 #define	callout_stop(c)		_callout_stop_safe(c, 0)
 int	_callout_stop_safe(struct callout *, int);