From 3ddd1777d5be2b52f0a486cc297ea1c9a2e7efcf Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Sat, 19 Nov 2011 11:17:27 +0000
Subject: [PATCH] Simplify the usb_pause_mtx() function by factoring out the
 generic parts to the kernel's pause() function. The pause() function can now
 be used when cold != 0. Also assert that the timeout in system ticks must be
 positive.

Suggested by:	Bruce Evans
MFC after:	1 week
---
 sys/dev/usb/usb_util.c | 28 ++++++++--------------------
 sys/kern/kern_synch.c  | 28 +++++++++++++++++++++++-----
 2 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/sys/dev/usb/usb_util.c b/sys/dev/usb/usb_util.c
index a9b1d6f66ec2..4fe79c5b33d6 100644
--- a/sys/dev/usb/usb_util.c
+++ b/sys/dev/usb/usb_util.c
@@ -115,33 +115,21 @@ device_set_usb_desc(device_t dev)
  *
  * This function will delay the code by the passed number of system
  * ticks. The passed mutex "mtx" will be dropped while waiting, if
- * "mtx" is not NULL.
+ * "mtx" is different from NULL.
  *------------------------------------------------------------------------*/
 void
-usb_pause_mtx(struct mtx *mtx, int _ticks)
+usb_pause_mtx(struct mtx *mtx, int timo)
 {
 	if (mtx != NULL)
 		mtx_unlock(mtx);
 
-	if (cold) {
-		/* convert to milliseconds */
-		_ticks = (_ticks * 1000) / hz;
-		/* convert to microseconds, rounded up */
-		_ticks = (_ticks + 1) * 1000;
-		DELAY(_ticks);
+	/*
+	 * Add one tick to the timeout so that we don't return too
+	 * early! Note that pause() will assert that the passed
+	 * timeout is positive and non-zero!
+	 */
+	pause("USBWAIT", timo + 1);
 
-	} else {
-
-		/*
-		 * Add one to the number of ticks so that we don't return
-		 * too early!
-		 */
-		_ticks++;
-
-		if (pause("USBWAIT", _ticks)) {
-			/* ignore */
-		}
-	}
 	if (mtx != NULL)
 		mtx_lock(mtx);
 }
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index a2c26ae10413..f4a84942d2ee 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -325,16 +325,34 @@ msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo)
 }
 
 /*
- * pause() is like tsleep() except that the intention is to not be
- * explicitly woken up by another thread.  Instead, the current thread
- * simply wishes to sleep until the timeout expires.  It is
- * implemented using a dummy wait channel.
+ * pause() is almost like tsleep() except that the intention is to not
+ * be explicitly woken up by another thread. Instead, the current
+ * thread simply wishes to sleep until the timeout expires.  It is
+ * implemented using a dummy wait channel. During cold bootup pause()
+ * will use the DELAY() function instead of tsleep() to wait the given
+ * number of system ticks. The passed "timo" argument must not be
+ * negative and also greater than zero.
  */
 int
 pause(const char *wmesg, int timo)
 {
 
-	KASSERT(timo != 0, ("pause: timeout required"));
+	KASSERT(timo > 0, ("pause: a positive and non-zero "
+	    "timeout is required"));
+
+	if (cold) {
+		/*
+		 * We delay one HZ at a time to avoid overflowing the
+		 * DELAY() argument:
+		 */
+		while (timo >= hz) {
+			DELAY(1000000);
+			timo -= hz;
+		}
+		if (timo > 0)
+			DELAY(timo * tick);
+		return (0);
+	}
 	return (tsleep(&pause_wchan, 0, wmesg, timo));
 }