Re: gnutls infloop possibly fixed

[Ted Zlatanov <tzz@lifelogs.com>]

On Sat, 11 Feb 2012 18:10:23 +0100 Lars Ingebrigtsen <larsi@gnus.org> wrote: 

LI> I finally took a hard look at the GnuTLS-related Emacs hangs.  It turned
LI> out to be pretty easy to reproduce for me.  If I switch off the wifi on
LI> this laptop and then presses `g' in Gnus, Emacs would reliably use 100%
LI> CPU, and `C-g' or anything wouldn't work.  So a totally dead Emacs.

LI> I chased this down to emacs_gnutls_write, which would just, well,
LI> infloop if libgnutls returned EAGAIN.  I've now removed that, and just
LI> leaves the normal Emacs process loop to retry if we get an EAGAIN.

LI> This seems to work for me -- `C-g' reliably works for me if I drop the
LI> network, or I get a new IP address.

LI> There may be other side-effects, though.  Slower throughput?  I don't
LI> know.  Please give it a whirl and report back whether things stop
LI> working or not.

Thanks!  I have just one question: can we, instead of aborting on
EAGAIN, retry a few times?  My suggestion is below.  Maybe we could wait
a millisecond, too.  Or is all that handled at the Emacs process loop
level?

Thanks
Ted

=== modified file 'src/gnutls.c'
--- src/gnutls.c        2012-02-11 17:06:14 +0000
+++ src/gnutls.c        2012-02-12 02:46:24 +0000
@@ -341,6 +341,7 @@
 EMACS_INT
 emacs_gnutls_write (struct Lisp_Process *proc, const char *buf, EMACS_INT nbyte)
 {
+  int retries = 10;
   ssize_t rtnval = 0;
   EMACS_INT bytes_written;
   gnutls_session_t state = proc->gnutls_state;
@@ -365,6 +366,8 @@
        {
          if (rtnval == GNUTLS_E_INTERRUPTED)
            continue;
+          if (rtnval == GNUTLS_E_AGAIN && retries-- > 0)
+           continue;
          else
            break;
        }