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Commit332693e
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lwlock: Fix, currently harmless, bug in LWLockWakeup()
Accidentally the code in LWLockWakeup() checked the list of to-be-woken upprocesses to see if LW_FLAG_HAS_WAITERS should be unset. That means thatHAS_WAITERS would not get unset immediately, but only during the next,unnecessary, call to LWLockWakeup().Luckily, as the code stands, this is just a small efficiency issue.However, if there were (as in a patch of mine) a case in which LWLockWakeup()would not find any backend to wake, despite the wait list not being empty,we'd wrongly unset LW_FLAG_HAS_WAITERS, leading to potentially hanging.While the consequences in the backbranches are limited, the code as-isconfusing, and it is possible that there are workloads where the additionalwait list lock acquisitions hurt, therefore backpatch.Discussion:https://postgr.es/m/fvfmkr5kk4nyex56ejgxj3uzi63isfxovp2biecb4bspbjrze7@az2pljabhnffBackpatch-through: 141 parentea36c2f commit332693e
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