From 817bf5d4a6fc86d2f35f521bb8dfe3bcc136e355 Mon Sep 17 00:00:00 2001
From: Jake Burkholder <jake@FreeBSD.org>
Date: Mon, 11 Sep 2000 00:20:02 +0000
Subject: [PATCH] Rename tsleep to msleep and add a mutex argument, which is
 released before sleeping and re-acquired before msleep returns.  A
 compatibility cpp macro has been provided for tsleep to avoid changing all
 occurences of it in the kernel.

Remove an assertion that the Giant mutex be held before
calling tsleep or asleep.

This is intended to serve the same purpose as condition
variables, but does not preclude their addition in the
future.

Approved by:	jasone
Obtained from:	BSD/OS
---
 sys/kern/kern_synch.c | 23 +++++++++++++++++++----
 sys/sys/param.h       |  1 +
 sys/sys/systm.h       |  5 ++++-
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 6c53f8f24ac..cd41140e552 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -408,10 +408,15 @@ sleepinit(void)
  * signal needs to be delivered, ERESTART is returned if the current system
  * call should be restarted if possible, and EINTR is returned if the system
  * call should be interrupted by the signal (return EINTR).
+ *
+ * The mutex argument is exited before the caller is suspended, and
+ * entered before msleep returns.  If priority includes the PDROP
+ * flag the mutex is not entered before returning.
  */
 int
-tsleep(ident, priority, wmesg, timo)
+msleep(ident, mtx, priority, wmesg, timo)
 	void *ident;
+	mtx_t *mtx;
 	int priority, timo;
 	const char *wmesg;
 {
@@ -419,14 +424,22 @@ tsleep(ident, priority, wmesg, timo)
 	int s, sig, catch = priority & PCATCH;
 	struct callout_handle thandle;
 	int rval = 0;
+	WITNESS_SAVE_DECL(mtx);
 
 #ifdef KTRACE
 	if (p && KTRPOINT(p, KTR_CSW))
 		ktrcsw(p->p_tracep, 1, 0);
 #endif
-	mtx_assert(&Giant, MA_OWNED);
+	WITNESS_SLEEP(0, mtx);
 	mtx_enter(&sched_lock, MTX_SPIN);
 
+	if (mtx != NULL) {
+		WITNESS_SAVE(mtx, mtx);
+		mtx_exit(mtx, MTX_DEF | MTX_NOSWITCH);
+		if (priority & PDROP)
+			mtx = NULL;
+	}
+
 	s = splhigh();
 	if (cold || panicstr) {
 		/*
@@ -527,7 +540,10 @@ out:
 	if (KTRPOINT(p, KTR_CSW))
 		ktrcsw(p->p_tracep, 0, 0);
 #endif
-
+	if (mtx != NULL) {
+		mtx_enter(mtx, MTX_DEF);
+		WITNESS_RESTORE(mtx, mtx);
+	}
 	return (rval);
 }
 
@@ -600,7 +616,6 @@ await(int priority, int timo)
 	int rval = 0;
 	int s;
 
-	mtx_assert(&Giant, MA_OWNED);
 	mtx_enter(&sched_lock, MTX_SPIN);
 
 	s = splhigh();
diff --git a/sys/sys/param.h b/sys/sys/param.h
index 9797feb93cd..7ac0290e6e5 100644
--- a/sys/sys/param.h
+++ b/sys/sys/param.h
@@ -116,6 +116,7 @@
 
 #define	PRIMASK	0x0ff
 #define	PCATCH	0x100		/* OR'd with pri for tsleep to check signals */
+#define	PDROP	0x200	/* OR'd with pri to stop re-entry of interlock mutex */
 
 #define	NZERO	0		/* default "nice" */
 
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index 0e8f9bbd35a..bd4cda686dc 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -92,6 +92,7 @@ extern int bootverbose;		/* nonzero to print verbose messages */
 
 struct clockframe;
 struct malloc_type;
+struct mtx;
 struct proc;
 struct timeval;
 struct tty;
@@ -318,7 +319,9 @@ extern watchdog_tickle_fn	wdog_tickler;
  * Common `proc' functions are declared here so that proc.h can be included
  * less often.
  */
-int	tsleep __P((void *chan, int pri, const char *wmesg, int timo));
+int	msleep __P((void *chan, struct mtx *mtx, int pri, const char *wmesg,
+		    int timo));
+#define	tsleep(chan, pri, wmesg, timo)	msleep(chan, NULL, pri, wmesg, timo)
 int	asleep __P((void *chan, int pri, const char *wmesg, int timo));
 int	await  __P((int pri, int timo));
 void	wakeup __P((void *chan));