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Add a new debug flag, DEBUG_LOCKREQS, which logs only lock requests.

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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.
This commit is contained in:
Greg Lehey 2001-05-22 02:34:30 +00:00
parent cf65a3dc63
commit c4d4f4147d
1 changed files with 25 additions and 12 deletions
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37
sys/dev/vinum/vinumlock.c
View File

@ -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 */