Re: wait_reading_process_ouput hangs in certain cases (w/ patches)

[Robert Pluim <rpluim@gmail.com>]

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Robert Pluim <rpluim@gmail.com> writes:

> Matthias Dahl <ml_emacs-lists@binary-island.eu> writes:
>
>> -	      if (set)
>> -		Available = tls_available;
>> +              for (channel = 0; channel < FD_SETSIZE; ++channel)
>> +                if (! NILP (chan_process[channel]))
>> +                  {
>> +                    struct Lisp_Process *p =
>> +                      XPROCESS (chan_process[channel]);
>> +
>> +                    if (just_wait_proc && p != wait_proc)
>> +                      continue;
>> +
>> +                    if (p && p->gnutls_p && p->gnutls_state
>> +                        && ((emacs_gnutls_record_check_pending
>> +                             (p->gnutls_state))
>> +                            > 0))
>> +                      {
>> +                        nfds++;
>> +                        eassert (p->infd == channel);
>> +                        FD_SET (p->infd, &Available);
>> +                      }
>> +                  }
>>  	    }
>>  #endif
>>  	}
>
> Hi Matthias, I apologize if this has already been mentioned, but did
> you check that this doesn't undo the fix for Bug#21337? The issue
> there as I recall was that FD's were set in Available that didn't
> actually have data to read, hence the need to check the TLS FD's
> separately using tls_available.

Answering my own question: your second patch undoes the fix for
21337. I think it needs to look something like this (I've put some of
the tabs back in to make the diff clearer, adjust according to taste):


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diff --git a/src/process.c b/src/process.c
index 11d914aab2..71b638726f 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5392,58 +5392,36 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 #endif	/* !HAVE_GLIB */
 
 #ifdef HAVE_GNUTLS
-          /* GnuTLS buffers data internally.  In lowat mode it leaves
-             some data in the TCP buffers so that select works, but
-             with custom pull/push functions we need to check if some
-             data is available in the buffers manually.  */
-          if (nfds == 0)
+          /* GnuTLS buffers data internally. select() will only report
+             available data for the underlying kernel sockets API, not
+             what has been buffered internally. As such, we need to loop
+             through all channels and check for available data manually.  */
+          if (nfds >= 0)
 	    {
 	      fd_set tls_available;
 	      int set = 0;
 
 	      FD_ZERO (&tls_available);
-	      if (! wait_proc)
-		{
-		  /* We're not waiting on a specific process, so loop
-		     through all the channels and check for data.
-		     This is a workaround needed for some versions of
-		     the gnutls library -- 2.12.14 has been confirmed
-		     to need it.  See
-		     http://comments.gmane.org/gmane.emacs.devel/145074 */
-		  for (channel = 0; channel < FD_SETSIZE; ++channel)
-		    if (! NILP (chan_process[channel]))
-		      {
-			struct Lisp_Process *p =
-			  XPROCESS (chan_process[channel]);
-			if (p && p->gnutls_p && p->gnutls_state
-			    && ((emacs_gnutls_record_check_pending
-				 (p->gnutls_state))
-				> 0))
-			  {
-			    nfds++;
-			    eassert (p->infd == channel);
-			    FD_SET (p->infd, &tls_available);
-			    set++;
-			  }
-		      }
-		}
-	      else
-		{
-		  /* Check this specific channel.  */
-		  if (wait_proc->gnutls_p /* Check for valid process.  */
-		      && wait_proc->gnutls_state
-		      /* Do we have pending data?  */
-		      && ((emacs_gnutls_record_check_pending
-			   (wait_proc->gnutls_state))
-			  > 0))
-		    {
-		      nfds = 1;
-		      eassert (0 <= wait_proc->infd);
-		      /* Set to Available.  */
-		      FD_SET (wait_proc->infd, &tls_available);
-		      set++;
-		    }
-		}
+              for (channel = 0; channel < FD_SETSIZE; ++channel)
+                if (! NILP (chan_process[channel]))
+                  {
+                    struct Lisp_Process *p =
+                      XPROCESS (chan_process[channel]);
+
+                    if (just_wait_proc && p != wait_proc)
+                      continue;
+
+                    if (p && p->gnutls_p && p->gnutls_state
+                        && ((emacs_gnutls_record_check_pending
+                             (p->gnutls_state))
+                            > 0))
+                      {
+                        nfds++;
+                        eassert (p->infd == channel);
+                        FD_SET (p->infd, &tls_available);
+                        set++;
+                      }
+                  }
 	      if (set)
 		Available = tls_available;
 	    }