Date: Wed, 25 Nov 1998 10:10:29 -0800 From: Mike Smith <mike@smith.net.au> To: HighWind Software Information <info@highwind.com> Cc: mike@smith.net.au, current@FreeBSD.ORG Subject: Re: Resend Message-ID: <199811251810.KAA01308@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 25 Nov 1998 13:03:36 EST." <199811251803.NAA02326@highwind.com>
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> Mike,
>
> > > I'm trying to track a problem where a "write()" to a socket
> > > sends the beginning of the data over and over.
> > >
> > > I'm looking at "sosend()" in uipc_socket.c, a comment says:
> > >
> > > > * Returns nonzero on error, timeout or signal; callers
> > > > * must check for short counts if EINTR/ERESTART are returned.
> > > > * Data and control buffers are freed on return.
> > >
> > > However, I don't see anywhere in the code where it returns
> > > EINTR/ERESTART. That is, if this code mistakenly loops when it gets
> > > interrupted or does a partial write(), it would result in the behavior
> > > I am seeing.
>
> > The sblock() macro can return this.
>
> Really???
>
> #define sblock(sb, wf) ((sb)->sb_flags & SB_LOCK ? \
> (((wf) == M_WAITOK) ? sb_lock(sb) : EWOULDBLOCK) : \
> ((sb)->sb_flags |= SB_LOCK), 0)
>
> That doesn't look like it. Did I miss something?
The implementation of sb_lock():
sb_lock(sb)
register struct sockbuf *sb;
{
int error;
while (sb->sb_flags & SB_LOCK) {
sb->sb_flags |= SB_WANT;
error = tsleep((caddr_t)&sb->sb_flags,
(sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK|PCATCH,
"sblock", 0);
if (error)
return (error);
}
sb->sb_flags |= SB_LOCK;
return (0);
}
see tsleep(9)
> > You'll also get this behaviour if the socket is nonblocking and you
> > only make a partial write, but forget to update your buffer pointer/
> > count before calling write() again.
>
> True. But, my reading of the libc_r write() code looks like it handles
> this perfectly. Maybe I missed something. On the outside, the descriptors
> are blocking, John Birrell's libc_r code loops and handles this correctly.
>
> I haven't been able to find any problems with that code. Maybe I missed
> something. It is in "lib/libc_r/uthread/uthread_write.c"
It appears to do the correct thing in the nonblocking case; this points
the finger at your application.
--
\\ Sometimes you're ahead, \\ Mike Smith
\\ sometimes you're behind. \\ mike@smith.net.au
\\ The race is long, and in the \\ msmith@freebsd.org
\\ end it's only with yourself. \\ msmith@cdrom.com
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