Hi In walsender.c, walreceiver.c, walreceiverfuncs.c there are several places where volatile qualifiers are used apparently only to prevent reordering around spinlock operations. My understanding is that if potential load/store reordering around spinlock operations is the only reason for using volatile, 0709b7ee72e4bc71ad07b7120acd117265ab51d0 made it unnecessary. For example see 6ba4ecbf477e0b25dd7bde1b0c4e07fc2da19348 which stripped some volatile qualifiers out of xlog.c.
I did notice that sometimes walsnd->pid is read without acquiring the spinlock. Is that actually OK anyway (taking a stale and inconsistent view of the contents of walsnd->pid WRT to the other members that are later accessed while holding the spinlock)? Would it be safe to remove all those volatile qualifiers, something like in the attached, or am I missing something? (There is also code in syncrep.c that is reading shmem without acquiring spinlocks using volatile qualifiers, that is a different situation, though I don't yet see how it is ordering sensitive or reading the same object repeatedly, but I'm not talking about that here). -- Thomas Munro http://www.enterprisedb.com
replication-strip-volatile.patch
Description: Binary data
-- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
