diff options
Diffstat (limited to 'src/include/storage/lock.h')
| -rw-r--r-- | src/include/storage/lock.h | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/src/include/storage/lock.h b/src/include/storage/lock.h index 7dea1b2a32c..c0fb08a989f 100644 --- a/src/include/storage/lock.h +++ b/src/include/storage/lock.h @@ -379,6 +379,20 @@ typedef struct PROCLOCK * shared memory. We also track the number of lock acquisitions per * ResourceOwner, so that we can release just those locks belonging to a * particular ResourceOwner. + * + * When holding a lock taken "normally", the lock and proclock fields always + * point to the associated objects in shared memory. However, if we acquired + * the lock via the fast-path mechanism, the lock and proclock fields are set + * to NULL, since there probably aren't any such objects in shared memory. + * (If the lock later gets promoted to normal representation, we may eventually + * update our locallock's lock/proclock fields after finding the shared + * objects.) + * + * Caution: a locallock object can be left over from a failed lock acquisition + * attempt. In this case its lock/proclock fields are untrustworthy, since + * the shared lock object is neither held nor awaited, and hence is available + * to be reclaimed. If nLocks > 0 then these pointers must either be valid or + * NULL, but when nLocks == 0 they should be considered garbage. */ typedef struct LOCALLOCKTAG { @@ -404,13 +418,13 @@ typedef struct LOCALLOCK LOCALLOCKTAG tag; /* unique identifier of locallock entry */ /* data */ - LOCK *lock; /* associated LOCK object in shared mem */ - PROCLOCK *proclock; /* associated PROCLOCK object in shmem */ + LOCK *lock; /* associated LOCK object, if any */ + PROCLOCK *proclock; /* associated PROCLOCK object, if any */ uint32 hashcode; /* copy of LOCKTAG's hash value */ int64 nLocks; /* total number of times lock is held */ int numLockOwners; /* # of relevant ResourceOwners */ int maxLockOwners; /* allocated size of array */ - bool holdsStrongLockCount; /* bumped FastPathStrongRelatonLocks? */ + bool holdsStrongLockCount; /* bumped FastPathStrongRelationLocks */ LOCALLOCKOWNER *lockOwners; /* dynamically resizable array */ } LOCALLOCK; |