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From: Charlie Brady <charlieb-supervision@budge.apana.org.au>
Newsgroups: gmane.comp.sysutils.supervision.general
Subject: Re: runsv and EAGAIN
Date: Fri, 11 Jul 2008 21:27:56 -0400 (EDT)
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On Fri, 11 Jul 2008, Charlie Brady wrote:

> Here's a sample strace:
>
> rt_sigprocmask(SIG_UNBLOCK, [TERM], NULL, 8) = 0
> rt_sigprocmask(SIG_UNBLOCK, [CHLD], NULL, 8) = 0
> poll([{fd=3, events=POLLIN}, {fd=9, events=POLLIN, revents=POLLIN}, {fd=11, 
> events=POLLIN}], 3, 1000020) = 1
> rt_sigprocmask(SIG_BLOCK, [TERM], NULL, 8) = 0
> rt_sigprocmask(SIG_BLOCK, [CHLD], NULL, 8) = 0
> read(3, 0xbfa256c3, 1)                  = -1 EAGAIN (Resource temporarily 
> unavailable)
> waitpid(-1, 0xbfa256bc, WNOHANG)        = 0
> read(9, "", 1)                          = 0
> read(11, 0xbfa256c3, 1)                 = -1 EAGAIN (Resource temporarily 
> unavailable)
> gettimeofday({1215792640, 591768}, NULL) = 0
...
> ...
> ERRORS
>        The poll() function shall fail if:
>
>       EAGAIN The allocation of internal data structures failed but a 
> subsequent request may succeed.
>
> ...

Sorry - this, from "man 3 read" is the relevant manpage section:

...
ERRORS
        EAGAIN Non-blocking I/O has been selected using O_NONBLOCK and no
        data was  immediately available for reading.
...

So poll i saying that data is available, and read is saying that it isn't. 
Is anyone else confused?