Avoid duplicate calls to current_timespec

* src/process.c (wait_reading_process_output):
Cache current_timespec results as long as we're not waiting.

1 files changed, 29 insertions, 15 deletions

diff --git a/src/process.c b/src/process.c
index 8a8dad793ad..9d8fa2237f3 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)