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Remove redundant PGPROC.lockGroupLeaderIdentifier field.

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We don't really need this field, because it's either zero or redundant with
PGPROC.pid.  The use of zero to mark "not a group leader" is not necessary
since we can just as well test whether lockGroupLeader is NULL.  This does
not save very much, either as to code or data, but the simplification seems
worthwhile anyway.
This commit is contained in:
Tom Lane
2016-02-22 11:20:35 -05:00
parent ea56b06cf7
commit 73bf8715aa
3 changed files with 25 additions and 25 deletions
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12
src/backend/storage/lmgr/proc.c
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@@ -401,7 +401,6 @@ InitProcess(void)
pg_atomic_init_u32(&MyProc->procArrayGroupNext, INVALID_PGPROCNO);
/* Check that group locking fields are in a proper initial state. */
Assert(MyProc->lockGroupLeaderIdentifier == 0);
Assert(MyProc->lockGroupLeader == NULL);
Assert(dlist_is_empty(&MyProc->lockGroupMembers));
@@ -565,7 +564,6 @@ InitAuxiliaryProcess(void)
SwitchToSharedLatch();
/* Check that group locking fields are in a proper initial state. */
Assert(MyProc->lockGroupLeaderIdentifier == 0);
Assert(MyProc->lockGroupLeader == NULL);
Assert(dlist_is_empty(&MyProc->lockGroupMembers));
@@ -822,7 +820,6 @@ ProcKill(int code, Datum arg)
dlist_delete(&MyProc->lockGroupLink);
if (dlist_is_empty(&leader->lockGroupMembers))
{
leader->lockGroupLeaderIdentifier = 0;
leader->lockGroupLeader = NULL;
if (leader != MyProc)
{
@@ -1771,7 +1768,6 @@ BecomeLockGroupLeader(void)
leader_lwlock = LockHashPartitionLockByProc(MyProc);
LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
MyProc->lockGroupLeader = MyProc;
MyProc->lockGroupLeaderIdentifier = MyProcPid;
dlist_push_head(&MyProc->lockGroupMembers, &MyProc->lockGroupLink);
LWLockRelease(leader_lwlock);
}
@@ -1795,6 +1791,9 @@ BecomeLockGroupMember(PGPROC *leader, int pid)
/* Group leader can't become member of group */
Assert(MyProc != leader);
/* Can't already be a member of a group */
Assert(MyProc->lockGroupLeader == NULL);
/* PID must be valid. */
Assert(pid != 0);
@@ -1808,9 +1807,10 @@ BecomeLockGroupMember(PGPROC *leader, int pid)
leader_lwlock = LockHashPartitionLockByProc(leader);
LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
/* Try to join the group */
if (leader->lockGroupLeaderIdentifier == pid)
/* Is this the leader we're looking for? */
if (leader->pid == pid && leader->lockGroupLeader == leader)
{
/* OK, join the group */
ok = true;
MyProc->lockGroupLeader = leader;
dlist_push_tail(&leader->lockGroupMembers, &MyProc->lockGroupLink);