Messages in this thread | | | From | Kyle Moffett <> | Subject | Re: PROBLEM: pthread-safety bug in write(2) on Linux 2.6.x | Date | Thu, 13 Apr 2006 06:28:12 -0400 |
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On Apr 13, 2006, at 05:56:08, Andrew Morton wrote: > Dan Bonachea <bonachead@comcast.net> wrote: >> >> This problem arose in the parallel runtime system for a scientific >> language compiler (nearly a million lines of code total - >> definitely a "real-world" program) - the example code is merely a >> pared-down demonstration of the problem. In parallel scientific >> computing, it's very common for many threads to be writing to >> stdout (usually for monitoring purposes) and it's expected and >> normal for output from separate threads to be arbitrarily >> interleaved, but it's *not* ok for output to be lost entirely. >> This is essentially equivalent to the real-world example you gave >> of many threads logging to a file. > > Interesting - afaik that's the first time this has been hit in a > real application.
I would guess that it could also be a problem with a wide variety of Perl CGIs running under Apache2+mod_perl with the worker threading model. In fact this may actually explain some odd behavior I got from one such module that I "fixed" by switching to logging via syslog. I don't remember which module it was or what the exact problem was, but I think it seemed similar in nature. That is somewhat of a surprising and nonintuitive failure mode for logging, IMHO it would be nice to get fixed. I would imagine that this has probably been hit a number of times before, mysteriously fixed by changed userspace locking or subtle thread ordering, and written off as the mysterious effects of cosmic rays on RAM.
Cheers, Kyle Moffett
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