Re: EINTR under Linux

From: Robert Hancock
Date: Thu Jul 17 2008 - 21:28:19 EST

akineko wrote:

I have a socket program that is running flawlessly under Solaris.
When I re-compiled it under Linux (CentOS 5.1) and run it, I got the
following error:

recv() failed: Interrupted system call

This only occurs very infrequently (probably one out of a million
packets exchanged).

select() in my program is getting EINTR.

From the postings I found in the news group seem suggesting that it is
due to GC.

The GC sends signals to each thread which causes them all to enter a stop-the-world state. When the GC
is finished, all the threads are resumed. When the threads are resumed, any that were blocked in a
blocking system call (like poll()) will return with EINTR. Normally you would just retry the system call.

So, I added to check if the errno == EINTR and now my program seems
working fine.


My question I would like to ask in this group is:
Does this mean any system call under Linux could return empty-hand
with EINTR due to GC?
I usually assume fatal if system call returns -1.
It is quite painful to check all system-call return status.

My second question is:
Does this can occur in other OS's? (free-BSD, Solaris, ...)
Or, is this specific to Linux OS?

I'm not sure what the GC you're referring to is, but I assume it's using a signal handler for that stop signal. If the signal handler is not installed with the SA_RESTART flag, then if a system call is interrupted by that signal it will get EINTR instead of being restarted automatically. For some system calls, EINTR can still occur, for example, see:

This is not Linux specific, but the specs allow for some different behavior between UNIX variants.
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