1 files changed, 46 insertions, 51 deletions

diff --git a/src/process.c b/src/process.c
index 6e5bcf307ab..15634e4a8b0 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5491,6 +5491,10 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
         }
       else
         {
+#ifdef HAVE_GNUTLS
+          int tls_nfds;
+          fd_set tls_available;
+#endif
           /* Set the timeout for adaptive read buffering if any
              process has non-zero read_output_skip and non-zero
              read_output_delay, and we are not reading output for a
@@ -5560,7 +5564,36 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
             }
 #endif
 
-/* Non-macOS HAVE_GLIB builds call thread_select in xgselect.c.  */
+#ifdef HAVE_GNUTLS
+          /* GnuTLS buffers data internally. We need to check if some
+             data is available in the buffers manually before the select.
+             And if so, we need to skip the select which could block. */
+          FD_ZERO (&tls_available);
+          tls_nfds = 0;
+          for (channel = 0; channel < FD_SETSIZE; ++channel)
+            if (! NILP (chan_process[channel])
+                && FD_ISSET (channel, &Available))
+              {
+                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)
+                  {
+                    tls_nfds++;
+                    eassert (p->infd == channel);
+                    FD_SET (p->infd, &tls_available);
+                  }
+              }
+          /* If wait_proc is somebody else, we have to wait in select
+             as usual.  Otherwise, clobber the timeout. */
+          if (tls_nfds > 0
+              && (!wait_proc ||
+                  (wait_proc->infd >= 0
+                   && FD_ISSET (wait_proc->infd, &tls_available))))
+            timeout = make_timespec (0, 0);
+#endif
+
+          /* Non-macOS HAVE_GLIB builds call thread_select in xgselect.c.  */
 #if defined HAVE_GLIB && !defined HAVE_NS
           nfds = xg_select (max_desc + 1,
                             &Available, (check_write ? &Writeok : 0),
@@ -5578,59 +5611,21 @@ 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)
+          /* Merge tls_available into Available. */
+          if (tls_nfds > 0)
             {
-              fd_set tls_available;
-              int set = 0;
-
-              FD_ZERO (&tls_available);
-              if (! wait_proc)
+              if (nfds == 0 || (nfds < 0 && errno == EINTR))
                 {
-                  /* 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.  */
-                  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++;
-                    }
+                  /* Fast path, just copy. */
+                  nfds = tls_nfds;
+                  Available = tls_available;
                 }
-              if (set)
-                Available = tls_available;
+              else if (nfds > 0)
+                /* Slow path, merge one by one.  Note: nfds does not need
+                   to be accurate, just positive is enough. */
+                for (channel = 0; channel < FD_SETSIZE; ++channel)
+                  if (FD_ISSET(channel, &tls_available))
+                    FD_SET(channel, &Available);
             }
 #endif
         }