PERFORCE change 100179 for review

[Kip Macy]

http://perforce.freebsd.org/chv.cgi?CH=100179

Change 100179 by kmacy at kmacy_storage:sun4v_work_sleepq on 2006/06/28 00:44:36

	my token of defiance against the most foul, kludgeish artifact
	in the entire kernel, the lockmgr
	- remove the LK_INTERNAL flag as the serialization provided by the interlock is not
	  meaningful for those already holding the lock

Affected files ...

.. //depot/projects/kmacy_sun4v/src/sys/kern/kern_lock.c#4 edit
.. //depot/projects/kmacy_sun4v/src/sys/sys/buf.h#4 edit
.. //depot/projects/kmacy_sun4v/src/sys/sys/lockmgr.h#4 edit

Differences ...

==== //depot/projects/kmacy_sun4v/src/sys/kern/kern_lock.c#4 (text+ko) ====

@@ -174,11 +174,6 @@
 	}
 #endif
 
-	if (flags & LK_INTERLOCK) {
-		mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED);
-		mtx_unlock(interlkp);
-	}
-
 	if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0)
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
 		    &lkp->lk_interlock->mtx_object,
@@ -468,33 +463,6 @@
 	return 0;
 }
 
-/*
- * Transfer any waiting processes from one lock to another.
- */
-void
-transferlockers(from, to)
-	struct lock *from;
-	struct lock *to;
-{
-
-	KASSERT(from != to, ("lock transfer to self"));
-	KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock"));
-
-	mtx_lock(from->lk_interlock);
-	if (from->lk_waitcount == 0) {
-		mtx_unlock(from->lk_interlock);
-		return;
-	}
-	from->lk_newlock = to;
-	wakeup((void *)from);
-	msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio,
-	    "lkxfer", 0);
-	from->lk_newlock = NULL;
-	from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE);
-	KASSERT(from->lk_waitcount == 0, ("active lock"));
-	mtx_unlock(from->lk_interlock);
-}
-
 
 /*
  * Initialize a lock; required before use.

==== //depot/projects/kmacy_sun4v/src/sys/sys/buf.h#4 (text+ko) ====

@@ -273,8 +273,10 @@
 	int s, ret;
 
 	s = splbio();
-	mtx_lock(bp->b_lock.lk_interlock);
-	locktype |= LK_INTERNAL;
+	/* XXX having the mutex didn't really remove the race for wmesg change
+	 * as there may still be other sleeping on the lock even when the interlock
+	 * mutex is held 
+	 */
 	bp->b_lock.lk_wmesg = buf_wmesg;
 	bp->b_lock.lk_prio = PRIBIO + 4;
 	ret = lockmgr(&(bp)->b_lock, locktype, interlock, curthread);
@@ -293,8 +295,11 @@
 	int s, ret;
 
 	s = splbio();
-	mtx_lock(bp->b_lock.lk_interlock);
-	locktype |= LK_INTERNAL | LK_TIMELOCK;
+	/* XXX having the mutex didn't really remove the race for wmesg change
+	 * as there may still be other sleeping on the lock even when the interlock
+	 * mutex is held 
+	 */
+	locktype |= LK_TIMELOCK;
 	bp->b_lock.lk_wmesg = wmesg;
 	bp->b_lock.lk_prio = (PRIBIO + 4) | catch;
 	bp->b_lock.lk_timo = timo;

==== //depot/projects/kmacy_sun4v/src/sys/sys/lockmgr.h#4 (text+ko) ====

@@ -141,7 +141,7 @@
 #define	LK_HAVE_EXCL	0x00040000	/* exclusive lock obtained */
 #define	LK_WAITDRAIN	0x00080000	/* process waiting for lock to drain */
 #define	LK_DRAINING	0x00100000	/* lock is being drained */
-#define	LK_INTERNAL	0x00200000/* The internal lock is already held */
+/*#define	LK_INTERNAL	0x00200000 The internal lock is already held */
 /*
  * Internal state flags corresponding to lk_sharecount, and lk_waitcount
  */