From c4d4f4147d11045012750f4e2fafad6de9a4dc5f Mon Sep 17 00:00:00 2001
From: Greg Lehey <grog@FreeBSD.org>
Date: Tue, 22 May 2001 02:34:30 +0000
Subject: [PATCH] Add a new debug flag, DEBUG_LOCKREQS, which logs only lock
 requests. Use this instead of DEBUG_LASTREQS to decide whether to log lock
 requests.

MFS:

vinumlock: Catch a potential race condition where one process is
           waiting for a lock, and between the time it is woken and
           it retries the lock, another process gets it and places it
           in the first entry in the table.

           This problem has not been observed, but it's possible, and
           it's easy enough to fix.

Submitted by:   tegge

vinumunlock: Catch a real bug capable of hanging a system.  When
             releasing a lock, vinumunlock() called wakeup_one.  This
             caused wakeups to sometimes get lost.  After due
             consideration, we think that this is due to the fact that
             you can't guarantee that some other process is also
             waiting on the same address.  This makes wakeup_one a
             very dangerous function to use.
---
 sys/dev/vinum/vinumlock.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/sys/dev/vinum/vinumlock.c b/sys/dev/vinum/vinumlock.c
index 801f13f50dd..f7d3f78c921 100644
--- a/sys/dev/vinum/vinumlock.c
+++ b/sys/dev/vinum/vinumlock.c
@@ -154,17 +154,18 @@ lockrange(daddr_t stripe, struct buf *bp, struct plex *plex)
 		if ((lock->stripe == stripe)		    /* it's our stripe */
 		&&(lock->bp != bp)) {			    /* but not our request */
 #ifdef VINUMDEBUG
-		    if (debug & DEBUG_LASTREQS) {
-			struct rangelock info;
+		    if (debug & DEBUG_LOCKREQS) {
+			struct rangelockinfo lockinfo;
 
-			info.stripe = stripe;
-			info.bp = bp;
-			logrq(loginfo_lockwait, (union rqinfou) &info, bp);
+			lockinfo.stripe = stripe;
+			lockinfo.bp = bp;
+			lockinfo.plexno = plex->plexno;
+			logrq(loginfo_lockwait, (union rqinfou) &lockinfo, bp);
 		    }
 #endif
 		    plex->lockwaits++;			    /* waited one more time */
 		    msleep(lock, &plex->lockmtx, PRIBIO, "vrlock", 0);
-		    lock = plex->lock;			    /* start again */
+		    lock = &plex->lock[-1];		    /* start again */
 		    foundlocks = 0;
 		    pos = NULL;
 		}
@@ -189,8 +190,14 @@ lockrange(daddr_t stripe, struct buf *bp, struct plex *plex)
     plex->usedlocks++;					    /* one more lock */
     mtx_unlock(&plex->lockmtx);
 #ifdef VINUMDEBUG
-    if (debug & DEBUG_LASTREQS)
-	logrq(loginfo_lock, (union rqinfou) pos, bp);
+    if (debug & DEBUG_LOCKREQS) {
+	struct rangelockinfo lockinfo;
+
+	lockinfo.stripe = stripe;
+	lockinfo.bp = bp;
+	lockinfo.plexno = plex->plexno;
+	logrq(loginfo_lock, (union rqinfou) &lockinfo, bp);
+    }
 #endif
     return pos;
 }
@@ -211,14 +218,20 @@ unlockrange(int plexno, struct rangelock *lock)
 	    &plex->lock[PLEX_LOCKS]);
 #endif
 #ifdef VINUMDEBUG
-    if (debug & DEBUG_LASTREQS)
-	logrq(loginfo_unlock, (union rqinfou) lock, lock->bp);
+    if (debug & DEBUG_LOCKREQS) {
+	struct rangelockinfo lockinfo;
+
+	lockinfo.stripe = lock->stripe;
+	lockinfo.bp = lock->bp;
+	lockinfo.plexno = plex->plexno;
+	logrq(loginfo_lockwait, (union rqinfou) &lockinfo, lock->bp);
+    }
 #endif
     lock->stripe = 0;					    /* no longer used */
     plex->usedlocks--;					    /* one less lock */
     if (plex->usedlocks == PLEX_LOCKS - 1)		    /* we were full, */
-	wakeup_one(&plex->usedlocks);			    /* get a waiter if one's there */
-    wakeup_one((void *) lock);
+	wakeup(&plex->usedlocks);			    /* get a waiter if one's there */
+    wakeup((void *) lock);
 }
 
 /* Get a lock for the global config, wait if it's not available */