VTRANS_LOCK;
for (tt = allTrans; tt; tt = nt) {
- nt = tt->next; /* remember in case we zap it */
if (tt->time + OLDTRANSWARN < now) {
Log("trans %u on volume %" AFS_VOLID_FMT " %s than %d seconds\n", tt->tid,
afs_printable_VolumeId_lu(tt->volid),
((tt->refCount > 0) ? "is older" : "has been idle for more"),
(((now - tt->time) / GCWAKEUP) * GCWAKEUP));
}
- if (tt->refCount > 0)
- continue;
- if (tt->time + OLDTRANSTIME < now) {
+ if ((tt->refCount <= 0) && (tt->time + OLDTRANSTIME < now)) {
Log("trans %u on volume %" AFS_VOLID_FMT " has timed out\n", tt->tid, afs_printable_VolumeId_lu(tt->volid));
tt->refCount++; /* we're using it now */
VTRANS_UNLOCK;
VPurgeVolume(&error, tt->volume);
+ /*
+ * While the lock was dropped, tt->next may have changed.
+ * Therefore, defer reading tt->next until _after_ we regain the lock.
+ */
VTRANS_LOCK;
}
-
- DeleteTrans(tt, 0); /* drops refCount or deletes it */
+ nt = tt->next;
+ /*
+ * DeleteTrans() will decrement tt->refCount; if it falls to 0, it will
+ * also delete tt itself. Therefore, we must read tt->next _before_
+ * calling DeleteTrans().
+ */
+ DeleteTrans(tt, 0);
GCDeletes++;
+ continue;
}
+ /*
+ * This path never dropped VTRANS_LOCK or modified the allTrans list.
+ * Therefore, no special care is required to determine the next trans in the chain.
+ */
+ nt = tt->next;
}
VTRANS_UNLOCK;
return 0;