[Emacs-diffs] master ad236260 8/8: Avoid duplicate calls to current_timespec

[Paul Eggert]

branch: master
commit ad23626030f0541e761f683661b51152128fb0b5
Author: Paul Eggert <address@hidden>
Commit: Paul Eggert <address@hidden>

    Avoid duplicate calls to current_timespec
    
    * src/process.c (wait_reading_process_output):
    Cache current_timespec results as long as we're not waiting.
---
 src/process.c |   44 +++++++++++++++++++++++++++++---------------
 1 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/src/process.c b/src/process.c
index 8a8dad7..9d8fa22 100644
--- a/src/process.c
+++ b/src/process.c
@@ -4591,6 +4591,9 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
   int got_some_output = -1;
   ptrdiff_t count = SPECPDL_INDEX ();
 
+  /* Close to the current time if known, an invalid timespec otherwise.  */
+  struct timespec now = invalid_timespec ();
+
   FD_ZERO (&Available);
   FD_ZERO (&Writeok);
 
@@ -4611,8 +4614,8 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
   else if (time_limit > 0 || nsecs > 0)
     {
       wait = TIMEOUT;
-      end_time = timespec_add (current_timespec (),
-                               make_timespec (time_limit, nsecs));
+      now = current_timespec ();
+      end_time = timespec_add (now, make_timespec (time_limit, nsecs));
     }
   else
     wait = INFINITY;
@@ -4637,7 +4640,8 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
       /* Exit if already run out.  */
       if (wait == TIMEOUT)
        {
-         struct timespec now = current_timespec ();
+         if (!timespec_valid_p (now))
+           now = current_timespec ();
          if (timespec_cmp (end_time, now) <= 0)
            break;
          timeout = timespec_sub (end_time, now);
@@ -4830,7 +4834,6 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
        }
       else
        {
-
          /* 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
@@ -4876,17 +4879,21 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
              && timespec_valid_p (timer_delay)
              && timespec_cmp (timer_delay, timeout) < 0)
            {
-             struct timespec timeout_abs = timespec_add (current_timespec (),
-                                                         timeout);
+             if (!timespec_valid_p (now))
+               now = current_timespec ();
+             struct timespec timeout_abs = timespec_add (now, timeout);
              if (!timespec_valid_p (got_output_end_time)
-                 || timespec_cmp (timeout_abs,
-                                  got_output_end_time) < 0)
+                 || timespec_cmp (timeout_abs, got_output_end_time) < 0)
                got_output_end_time = timeout_abs;
              timeout = timer_delay;
            }
          else
            got_output_end_time = invalid_timespec ();
 
+         /* NOW can become inaccurate if time can pass during pselect.  */
+         if (timeout.tv_sec > 0 || timeout.tv_nsec > 0)
+           now = invalid_timespec ();
+
 #if defined (HAVE_NS)
           nfds = ns_select
 #elif defined (HAVE_GLIB)
@@ -4965,14 +4972,21 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
              haven't lowered our timeout due to timers or SIGIO and
              have waited a long amount of time due to repeated
              timers.  */
-         struct timespec now = current_timespec ();
-          if (wait < TIMEOUT
-             || (wait == TIMEOUT && timespec_cmp (end_time, now) <= 0)
-             || (!process_skipped && got_some_output > 0
-                 && (!timespec_valid_p (got_output_end_time)
-                     || timespec_cmp (got_output_end_time, now) <= 0)
-                 && (timeout.tv_sec > 0 || timeout.tv_nsec > 0)))
+         if (wait < TIMEOUT)
            break;
+         struct timespec cmp_time
+           = (wait == TIMEOUT
+              ? end_time
+              : (!process_skipped && got_some_output > 0
+                 && (timeout.tv_sec > 0 || timeout.tv_nsec > 0))
+              ? got_output_end_time
+              : invalid_timespec ());
+         if (timespec_valid_p (cmp_time))
+           {
+             now = current_timespec ();
+             if (timespec_cmp (cmp_time, now) <= 0)
+               break;
+           }
        }
 
       if (nfds < 0)