Re: EINTR under Linux
From: Michael Kerrisk
Date: Mon Jul 21 2008 - 06:43:57 EST
On 7/18/08, Robert Hancock <hancockr@xxxxxxx> wrote:
> akineko wrote:
> > Hello,
> > 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.
And the signal.7 page has been very recently updated to include
Linux-specific details for most system calls. Have a look here:
Basically, recv() is restarted if you use SA_RESTART, but select() is
never restarted, regardless of SA_RESTART (and POSIX.1 allows this).
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