1 files changed, 27 insertions, 14 deletions

diff --git a/procps/top.c b/procps/top.c
index 89e5d5f67..a87fa0ae4 100644
--- a/procps/top.c
+++ b/procps/top.c
@@ -968,7 +968,7 @@ enum {
                 | PSSCAN_SMAPS
                 | PSSCAN_COMM,
         EXIT_MASK = 0,
-        NO_RESCAN_MASK = (unsigned)-1,
+        ONLY_REDRAW = (unsigned)-1,
 };
 
 #if ENABLE_FEATURE_TOP_INTERACTIVE
@@ -984,12 +984,19 @@ static unsigned handle_input(unsigned scan_mask, duration_t interval)
                 int32_t c, cc;
 
                 c = safe_read_key(STDIN_FILENO, G.kbd_input, interval * 1000);
-                if (c == -1 && errno != EAGAIN) {
-                        /* error/EOF */
-                        option_mask32 |= OPT_EOF;
+                if (c == -1) {
+                        if (errno != EAGAIN)
+                                /* error/EOF */
+                                option_mask32 |= OPT_EOF;
+                        /* else: timeout - rescan and refresh */
                         break;
                 }
                 interval = 0;
+                /* "continue" statements below return to do one additional
+                 * quick attempt to read a key. This prevents
+                 * long sequence of e.g. "nnnnnnnnnnnnnnnnnnnnnnnnnn"
+                 * to cause lots of rescans.
+                 */
 
                 if (c == initial_settings.c_cc[VINTR])
                         return EXIT_MASK;
@@ -1023,7 +1030,7 @@ static unsigned handle_input(unsigned scan_mask, duration_t interval)
                                 G_scroll_ofs = ntop - 1;
                         if (G_scroll_ofs < 0)
                                 G_scroll_ofs = 0;
-                        return NO_RESCAN_MASK;
+                        return ONLY_REDRAW;
                 }
 
                 cc = c;
@@ -1083,7 +1090,7 @@ static unsigned handle_input(unsigned scan_mask, duration_t interval)
                 if (c == 's') {
                         sort_field = (sort_field + 1) % NUM_SORT_FIELD;
                         if (scan_mask == TOPMEM_MASK)
-                                return NO_RESCAN_MASK;
+                                return ONLY_REDRAW;
                         scan_mask = TOPMEM_MASK;
                         free(prev_hist);
                         prev_hist = NULL;
@@ -1093,7 +1100,7 @@ static unsigned handle_input(unsigned scan_mask, duration_t interval)
 #  endif
                 if (c == 'r') {
                         inverted ^= 1;
-                        continue;
+                        return ONLY_REDRAW;
                 }
 #  if ENABLE_FEATURE_TOP_SMP_CPU
                 /* procps-2.0.18 uses 'C', 3.2.7 uses '1' */
@@ -1115,8 +1122,8 @@ static unsigned handle_input(unsigned scan_mask, duration_t interval)
                 }
 #  endif
 # endif
-                break; /* unknown key -> force refresh */
-        }
+                /* Unknown key. Eat remaining buffered input (if any) */
+        } /* while (1) */
 
         return scan_mask;
 }
@@ -1253,7 +1260,7 @@ int top_main(int argc UNUSED_PARAM, char **argv)
 #endif
 
         while (scan_mask != EXIT_MASK) {
-                IF_FEATURE_TOP_INTERACTIVE(unsigned new_mask;)
+                IF_FEATURE_TOP_INTERACTIVE(unsigned new_mask = scan_mask;)
                 procps_status_t *p = NULL;
 
                 if (OPT_BATCH_MODE) {
@@ -1337,7 +1344,7 @@ int top_main(int argc UNUSED_PARAM, char **argv)
                         qsort(topmem, ntop, sizeof(topmem_status_t), (void*)topmem_sort);
                 }
 #endif
- IF_FEATURE_TOP_INTERACTIVE(display:)
+ IF_FEATURE_TOP_INTERACTIVE(redraw:)
                 IF_FEATURE_TOPMEM(if (scan_mask != TOPMEM_MASK)) {
                         display_process_list(G.lines, col);
                 }
@@ -1353,9 +1360,15 @@ int top_main(int argc UNUSED_PARAM, char **argv)
                 clearmems();
                 sleep_for_duration(interval);
 #else
-                new_mask = handle_input(scan_mask, interval);
-                if (new_mask == NO_RESCAN_MASK)
-                        goto display;
+                new_mask = handle_input(scan_mask,
+                        /* After "redraw with no rescan", have one
+                         * key timeout shorter that normal
+                         * (IOW: rescan sooner):
+                         */
+                        (new_mask == ONLY_REDRAW ? 1 : interval)
+                );
+                if (new_mask == ONLY_REDRAW)
+                        goto redraw;
                 scan_mask = new_mask;
                 clearmems();
 #endif