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Fix thinko in lock mode enum

Browse Source 
Commit 0e5680f473 contained a thinko
mixing LOCKMODE with LockTupleMode.  This caused misbehavior in the case
where a tuple is marked with a multixact with at most a FOR SHARE lock,
and another transaction tries to acquire a FOR NO KEY EXCLUSIVE lock;
this case should block but doesn't.

Include a new isolation tester spec file to explicitely try all the
tuple lock combinations; without the fix it shows the problem:

    starting permutation: s1_begin s1_lcksvpt s1_tuplock2 s2_tuplock3 s1_commit
    step s1_begin: BEGIN;
    step s1_lcksvpt: SELECT * FROM multixact_conflict FOR KEY SHARE; SAVEPOINT foo;
    a

    1
    step s1_tuplock2: SELECT * FROM multixact_conflict FOR SHARE;
    a

    1
    step s2_tuplock3: SELECT * FROM multixact_conflict FOR NO KEY UPDATE;
    a

    1
    step s1_commit: COMMIT;

With the fixed code, step s2_tuplock3 blocks until session 1 commits,
which is the correct behavior.

All other cases behave correctly.

Backpatch to 9.3, like the commit that introduced the problem.
This commit is contained in:
Alvaro Herrera
2015-01-04 15:48:29 -03:00
parent 2ea95959af
commit d5e3d1e969
4 changed files with 537 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/backend/access/heap/heapam.c
View File

@ -6102,6 +6102,7 @@ DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
int nmembers;
MultiXactMember *members;
bool result = false;
LOCKMODE wanted = tupleLockExtraInfo[lockmode].hwlock;
allow_old = !(infomask & HEAP_LOCK_MASK) && HEAP_XMAX_IS_LOCKED_ONLY(infomask);
nmembers = GetMultiXactIdMembers(multi, &members, allow_old,
@ -6113,11 +6114,12 @@ DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
for (i = 0; i < nmembers; i++)
{
TransactionId memxid;
LockTupleMode memlockmode;
LOCKMODE memlockmode;
memlockmode = LOCKMODE_from_mxstatus(members[i].status);
/* ignore members that don't conflict with the lock we want */
if (!DoLockModesConflict(memlockmode, lockmode))
if (!DoLockModesConflict(memlockmode, wanted))
continue;
/* ignore members from current xact */