Allow a no-wait lock acquisition to succeed in more cases. We don't determine the position at which a process waiting for a lock should insert itself into the wait queue until we reach ProcSleep(), and we may at that point discover that we must insert ourselves ahead of everyone who wants a conflicting lock, in which case we obtain the lock immediately. Up until now, a no-wait lock acquisition would fail in such cases, erroneously claiming that the lock couldn't be obtained immediately. Fix that by trying ProcSleep even in the no-wait case.
No back-patch for now, because I'm treating this as an improvement to the existing no-wait feature. It could instead be argued that it's a bug fix, on the theory that there should never be any case whatsoever where no-wait fails to obtain a lock that would have been obtained immediately without no-wait, but I'm reluctant to interpret the semantics of no-wait that strictly. Robert Haas and Jingxian Li Discussion: http://postgr.es/m/ca+tgmobch-kmxgvpb0bb-inmdtcnktvcz4jbxdjows3kym+...@mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/2346df6fc373df9c5ab944eebecf7d3036d727de Modified Files -------------- src/backend/storage/lmgr/lock.c | 119 ++++++++++++++++------------ src/backend/storage/lmgr/proc.c | 20 ++++- src/include/storage/proc.h | 4 +- src/test/isolation/expected/lock-nowait.out | 9 +++ src/test/isolation/isolation_schedule | 1 + src/test/isolation/specs/lock-nowait.spec | 28 +++++++ 6 files changed, 128 insertions(+), 53 deletions(-)