Thomas Munro 6c0fb94189 Fix race in dsm_attach() when handles are reused. ... DSM handle values can be reused as soon as the underlying shared memory object has been destroyed. That means that for a brief moment we might have two DSM slots with the same handle. While trying to attach, if we encounter a slot with refcnt == 1, meaning that it is currently being destroyed, we should continue our search in case the same handle exists in another slot. The race manifested as a rare "dsa_area could not attach to segment" error, and was more likely in 10 and 11 due to the lack of distinct seed for random() in parallel workers. It was made very unlikely in in master by commit 197e4af9, and older releases don't usually create new DSM segments in background workers so it was also unlikely there. This fixes the root cause of bug report #15585, in which the error could also sometimes result in a self-deadlock in the error path. It's not yet clear if further changes are needed to avoid that failure mode. Back-patch to 9.4, where dsm.c arrived. Author: Thomas Munro Reported-by: Justin Pryzby, Sergei Kornilov Discussion: https://postgr.es/m/20190207014719.GJ29720@telsasoft.com Discussion: https://postgr.es/m/15585-324ff6a93a18da46@postgresql.org		2019-02-15 14:05:09 +13:00
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buffer	Update copyright for 2019	2019-01-02 12:44:25 -05:00
file	Update copyright for 2019	2019-01-02 12:44:25 -05:00
freespace	Avoid creation of the free space map for small heap relations, take 2.	2019-02-04 07:49:15 +05:30
ipc	Fix race in dsm_attach() when handles are reused.	2019-02-15 14:05:09 +13:00
large_object	Remove superfluous tqual.h includes.	2019-01-21 12:15:02 -08:00
lmgr	Move max_wal_senders out of max_connections for connection slot handling	2019-02-12 10:07:56 +09:00
page	Update copyright for 2019	2019-01-02 12:44:25 -05:00
smgr	In bootstrap mode, don't allow the creation of files if they don't already	2019-01-28 07:52:51 +05:30
Makefile	Remove cvs keywords from all files.	2010-09-20 22:08:53 +02:00