OK, thanks. ---------------------------------------------------------------------------
Scott Lamb wrote: > On Jan 30, 2004, at 4:53 PM, Bruce Momjian wrote: > >> Actually, thinking about this a bit more, that might not even be > >> necessary. Is SIGPIPE-via-(read|write) synchronous or asynchronous? > >> (I.e., is the SIGPIPE guaranteed to arrive during the offending system > >> call?) I was thinking not, but maybe yes. I can't seem to find a > >> straight answer. A lot of documents seem to confuse thread-directed > >> and > >> synchronous, when they're not quite the same thing. > >> SIGALRM-via-alarm() > >> is thread-directed but obviously asynchronous. > > > > SIGPIPE is a sychronous signal that is called during the read() in > > libpq. I am not sure what thread-directed is. > > Ahh, then the usage in libpq is safe; sorry for the false alarm. The > concerns about signal safety are really only for async signals, as the > behavior is undefined only when one async signal-unsafe function is > called from a signal interrupting another: > > "In the presence of signals, all functions defined by this volume of > IEEE?Std?1003.1-2001 shall behave as defined when called from or > interrupted by a signal-catching function, with a single exception: > when a signal interrupts an unsafe function and the signal-catching > function calls an unsafe function, the behavior is undefined." > > thread-directed, by the way, simply means that the signal is directed > at a specific thread, not just some thread in the process that doesn't > have it masked. It's the difference between kill() and pthread_kill(). > AFAIK, all synchronous signals are thread-directed, but not all > thread-directed signals are synchronous. > > Here the signal is synchronous, so the signal is guaranteed to happen > at a safe point (during the read()), so there's no problem. > > Thanks, > Scott Lamb > -- 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 4: Don't 'kill -9' the postmaster
