Build Postgres master, on Linux or another platform that will use the poll() implementation rather than the older select(). Send the Postmaster SIGKILL. Observe that the WAL Writer lives on, representing a denial of service as it stays attached to shared memory, busy waiting (evident from the fact that it quickly leaks memory).
WAL writer shouldn't do this. It isn't doing anything stupid like relying on the return value of WaitLatch(), which is documented to only reliably indicate certain wake events but not others. The main event loop calls PostmasterIsAlive(), which is supposed to be totally reliable. If I use the select() based latch implementation, it behaves just fine. I have some doubts about the latch usage within WAL Writer as things stands - it needs to be cleaned up a bit (I think it should use the process latch, because I'm paranoid about timeout invalidation issues now and in the future, plus it doesn't record errno in the handlers). These smaller issues are covered in passing in the group commit patch that Simon Riggs and I are currently working on in advance of the final 9.2 commitfest. In case it matters: [peter@peterlaptop postmaster]$ uname -a Linux peterlaptop 3.1.6-1.fc16.x86_64 #1 SMP Wed Dec 21 22:41:17 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux I'd debug this myself, but I'm a little bit preoccupied with group commit right now. The rationale for introducing the poll()-based implementation where available was that it performed better than a select()-based one. I wonder, how compelling a win is that expected to be? -- Peter Geoghegan http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers