On Mon, Apr 09, 2001 at 04:57:51PM -0700, Jim Wilcoxson wrote:
> I know that a sleep() call can return EINTR. It means an event like a
> signal delivery caused the sleep() system call to be interrupted.
>
> Not sure what it means if a read call returns this result, because
> EINTR (with sleep()) means that the system call did partially execute.
> So in the case of read(), it could be that part of the data requested
> was read. If that is true, it seems like the OS should return the
> number of bytes read instead of EINTR. If the read() did not execute
> and the file descriptor is non-blocking, read() could return zero or
> EAGAIN.
>
> Maybe this is a case where the f.d. is configured to block and read()
> has not yet read any data when the signal occurs. In that case,
> returning zero bytes usually means EOF (which is wrong), and returning
> EAGAIN is probably only legal on non-blocking descriptors. So it
> is returning EINTR. I think the thing to do is retry the read,
> although if you are having this problem in this specific case, it
> probably exists in other circumstances as well (not just exec).
>
> Jim
I agree that with you. It makes me wonder about other calls not being
wrapped properly. I will need to do more research on *BSD's to find out.
I wrapped it in a loop and re-read if EINTR is returned. It seems to be
working.
>
> >
> > On Mon, Apr 09, 2001 at 02:52:41PM -0500, Robert Hentosh wrote:
> > > I have been playing with aolserver on OpenBSD 2.8. aolserver 3.3.1
> > > now compiles cleanly on OpenBSD. And searching through the mailling
> > > lists the only other problem seems to be an issue with tcl exec command.
:: snip ::
> > Using ktrace on the nsd8x process and it seems that the read() from the
> > pipe to the fork'd process is receiving SIGCHLD:
> >
> > 6481 nsd8x CALL fstat(0x10,0x1a5aec)
> > 6481 nsd8x RET fstat 0
> > 6481 nsd8x CALL close(0x10)
> > 6481 nsd8x RET close 0
> > 6481 nsd8x CALL read(0xe,0x1ca020,0x1000)
> > 6481 nsd8x GIO fd 14 read 65 bytes
> > "bin
> > include
> > lib
> > log
> > modules
> > nsd8x.core
> > sample-config.tcl
> > servers
> > "
> > 6481 nsd8x RET read 65/0x41
> > 6481 nsd8x CALL read(0xe,0x1ca020,0x1000)
> > 6481 nsd8x PSIG SIGCHLD caught handler=0x4018b9b8 mask=0x0 code=0x0
> > 6481 nsd8x RET read -1 errno 4 Interrupted system call
> > 6481 nsd8x CALL fcntl(0,0x4,0x4)
> > 6481 nsd8x RET fcntl -1 errno 19 Operation not supported by device
> > 6481 nsd8x CALL fcntl(0x1,0x4,0x6)
> > 6481 nsd8x RET fcntl 0
> >
> > So it looks like to me that the read() at line 953 in tclUnixPipe.c is
> > getting the SIGCHLD on the second read() after it has obtained the
> > program output. I am not sure what the proper solution should be.
> >
> > Suggestions?
> >
