Re: PROBLEM: blocking read on socket repeatedly returns EAGAIN

[Kern Sibbald <kern@sibbald.com>]

On Tuesday 16 August 2005 16:03, Alan Cox wrote:
> On Maw, 2005-08-16 at 15:19 +0200, Kern Sibbald wrote:
> > have written, nor does it write() anything.  When my read() is issued, I
> > expect it to block, but it immediately returns with -1 and errno set to
> > EAGAIN.  If the read() is re-issued, a CPU intensive loop results as long
> > as the other end does not read() the data written to the socket.  This is
> > a multi-threaded program, but the other threads are all blocked on
> > something.
>
> You are describing behaviour as expected with nonblocking set. That
> suggests to me that something or someone set or inherited the nonblock
> flag on that socket. Is the strange behaviour specific to the latest
> kernel ?

Well, it looks like I have egg on my face; it is not a kernel problem.

Return value from fcntl(F_GETFL) in decimal, hex, octal:
rufus-fd: bnet.c:84 fcntl=2050 0x802 04002

Someone is setting nonblocking on my socket ! -- perhaps some thread library?  
Anyway, it is definitely not me, and this is a thread of the main program so 
I don't see inheritance as the problem. I'll track it down and send the bug 
report to the appropriate place.

Thanks for the fast response and sorry for the inconvenience.

Kern