At Mon, 20 Apr 2020 00:59:54 -0700, Noah Misch <n...@leadboat.com> wrote in > On Mon, Apr 20, 2020 at 04:15:40PM +0900, Kyotaro Horiguchi wrote: > > At Sat, 18 Apr 2020 00:01:42 -0700, Noah Misch <n...@leadboat.com> wrote in > > > On Fri, Apr 17, 2020 at 05:06:29PM +0900, Kyotaro Horiguchi wrote: > > > > At Fri, 17 Apr 2020 17:00:15 +0900 (JST), Kyotaro Horiguchi > > > > <horikyota....@gmail.com> wrote in > > > > > By the way, if latch is consumed in WalSndLoop, succeeding call to > > > > > WalSndWaitForWal cannot be woke-up by the latch-set. Doesn't that > > > > > cause missing wakeups? (in other words, overlooking of wakeup latch). > > > > > > > > - Since the only source other than timeout of walsender wakeup is latch, > > > > - we should avoid wasteful consuming of latch. (It is the same issue > > > > - with [1]). > > > > > > > > + Since walsender is wokeup by LSN advancement via latch, we should > > > > + avoid wasteful consuming of latch. (It is the same issue with [1]). > > > > > > > > > > > > > If wakeup signal is not remembered on walsender (like > > > > > InterruptPending), WalSndPhysical cannot enter a sleep with > > > > > confidence. > > > > > > No; per latch.h, "What must be avoided is placing any checks for > > > asynchronous > > > events after WaitLatch and before ResetLatch, as that creates a race > > > condition." In other words, the thing to avoid is calling ResetLatch() > > > without next examining all pending work that a latch would signal. Each > > > walsender.c WaitLatch call does follow the rules. > > > > I didn't meant that, of course. I thought of more or less the same > > with moving the trigger from latch to signal then the handler sets a > > flag and SetLatch(). If we use bare latch, we should avoid false > > entering to sleep, which also makes thinks compolex. > > I don't understand. If there's a defect, can you write a test case or > describe a sequence of events (e.g. at line X, variable Y has value Z)?
Indeed. Anyway the current version cannot have such a possible issue. Thanks. -- Kyotaro Horiguchi NTT Open Source Software Center
