Magnus Hagander wrote: > >We don't need the cancelConnLock if this is done properly (at least, > >assuming that storing a pointer is atomic, which seems reasonable). > > Are you sure about this? > Per what docs I have, storing a pointer should always be atomic. > exchanging two pointers are not, which is why at least win32 provides a > specific function to do that (InterlockedExchangePointer).
You can't even assume a pointer write is atomic to all threads if you have multiple CPUs. Assume two CPU's. Even if CPU 1 writes the pointer atomically, there is no guarantee that the other CPU will see the change at the same time. To guarantee it, you need a memory barrier like a lock/unlock. Some CPU systems guarantee memory conherency for memory operations, but some do not. It is temping to think that if one CPU can write a value atomically then the other CPU will also see it at the same time, but that isn't guaranteed. For the hardware issues see: http://www.javaworld.com/javaworld/jw-02-2001/jw-0209-toolbox.html -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html