$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.11 2002/07/19 00:17:40 momjian Exp $

$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.12 2002/10/31 21:34:16 tgl Exp $

LOCKING OVERVIEW

asynchronous invocation of deadlock checking. A deadlock cycle in the WFG

is formed when the last edge in the cycle is added; therefore the last

process in the cycle to wait (the one from which that edge is outgoing) is

certain to detect and resolve the cycle when it later runsHandleDeadLock.

certain to detect and resolve the cycle when it later runsCheckDeadLock.

This holds even if that edge addition created multiple cycles; the process

may indeed abort without ever noticing those additional cycles, but we

don't particularly care. The only other possible creation of deadlocks is

2. It is not certain that a deadlock will be resolved by aborting the

last-to-wait process. If earlier waiters in the cycle have not yet run

HandleDeadLock, then the first one to do so will be the victim.

CheckDeadLock, then the first one to do so will be the victim.

3. No live (wakable) process can be missed by ProcLockWakeup, since it

examines every member of the wait queue (this was not true in the 7.0

holder)!=STATUS_OK)

{