At Tue, 22 Dec 2020 02:48:22 +0000, "tsunakawa.ta...@fujitsu.com" <tsunakawa.ta...@fujitsu.com> wrote in > From: Amit Kapila <amit.kapil...@gmail.com> > > Why would all client backends wait for AccessExclusive lock on this > > relation? Say, a client needs a buffer for some other relation and > > that might evict this buffer after we release the lock on the > > partition. In StrategyGetBuffer, it is important to either have a pin > > on the buffer or the buffer header itself must be locked to avoid > > getting picked as victim buffer. Am I missing something? > > Ouch, right. (The year-end business must be making me crazy...) > > So, there are two choices here: > > 1) The current patch. > 2) Acquire the buffer header spinlock before releasing the buffer mapping > lwlock, and eliminate the buffer tag comparison as follows: > > BufTableLookup(); > LockBufHdr(); > LWLockRelease(); > InvalidateBuffer(); > > I think both are okay. If I must choose either, I kind of prefer 1), because > LWLockRelease() could take longer time to wake up other processes waiting on > the lwlock, which is not very good to do while holding a spinlock.
I like, as said before, the current patch. regareds. -- Kyotaro Horiguchi NTT Open Source Software Center
