On 2013-07-17 15:46:00 +0530, Amit Kapila wrote: > On Monday, July 08, 2013 2:47 PM Heikki Linnakangas wrote: > > Ok, I've committed this patch now. Finally, phew! > > Few doubts while reading the code: > > 1. Why in function WALInsertSlotAcquireOne(int slotno), it does > START_CRIT_SECTION() to > Lock out cancel/die interrupts, whereas other places call > HOLD_INTERRUPTS()
A crit section does more than just stopping interrupts. They also ensure that errors that occur while inside one get converted to a PANIC. That seems apt for SlotAcquire/Release. Although the comments could possibly improved a bit. > 2. In function GetXLogBuffer(), why the logic to wakeup waiters is > different when expectedEndPtr != endptr; > When the wakeupwaiters is done in case expectedEndPtr == endptr? I am not sure what you're asking here. We wakeup waiters if expectedEndPtr != endptr because that means the wal buffer page the 'ptr' fits on currently has different content. Which in turn means we've finished with the last page and progressed to a new one. So we wake up everyone waiting for us. WakeupWaiters() doesn't get passed expectedEndPtr but expectedEndPtr - XLOG_BLCKSZ (up to there we are guaranteed to have inserted successfully). And we're comparing with the xlogInsertingAt value which basically measures up to where we've successfully inserted. > 3. > static bool > ReserveXLogSwitch(..) > > In above function header, why EndPos_p/StartPos_p is used when > function arguments are EndPos/StartPos? I guess that's bitrot... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
