"Tom Lane" <[EMAIL PROTECTED]> writes: > Gregory Stark <[EMAIL PROTECTED]> writes: >> "Tom Lane" <[EMAIL PROTECTED]> writes: >>> How you figure that? > >> Well I'm not clear exactly what's going on with the semaphores here. If it's >> possible for to be printing the messages only as a result of another backend >> unlocking the semaphore then making the PGSemaphoreUnlock conditional on >> log_lock_waits means you can't enable log_lock_waits after startup and get >> deterministic behaviour because whether you get messages will depend on which >> other backend happens to wake you up. > > I don't see how you arrive at that conclusion. The message is printed > by the backend that is waiting for (or just obtained) a lock, dependent > on its own local setting of log_lock_waits, and not dependent on who > woke it up.
But in your version of the patch you're not calling PGSemaphoreUnlock() unless log_lock_waits is set in the process doing the waking. Hm, I suppose it'll wake up itself when its own deadlock timer runs out anyways. So I guess the worst case is that it doesn't say anything after a soft deadlock fixup. > BTW, I just noticed that GUC allows deadlock_timeout to be set all the > way down to zero. This seems bad --- surely the minimum value should at > least be positive? As CVS HEAD stands, you're likely to get a lot of > spurious/useless log messages if you have log_lock_waits = true and > deadlock_timeout = 0. Do we care? Does that actually work? I would expect setitimer to turn off the alarm in that case. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
