From 0457e6c24dee79703b4b69d7ff039eafcec16d03 Mon Sep 17 00:00:00 2001
From: dim <dim@FreeBSD.org>
Date: Fri, 27 Sep 2019 20:20:21 +0000
Subject: [PATCH] Make fractional delays for top(1) work for interactive mode.

In r334906, the -s option was changed to allow fractional times, but
this only functioned correctly for batch mode.  In interactive mode, any
delay below 1.0 would get floored to zero.  This would put top(1) into a
tight loop, which could be difficult to interrupt.

Fix this by storing the -s option value (after validation) into a struct
timeval, and using that struct consistently for delaying with select(2).

Next up is to allow interactive entry of a fractional delay value.

MFC after:	3 days
---
 usr.bin/top/top.1 |  2 +-
 usr.bin/top/top.c | 50 +++++++++++++++++++++++++----------------------
 2 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/usr.bin/top/top.1 b/usr.bin/top/top.1
index a26fbc181229..5b422fffe737 100644
--- a/usr.bin/top/top.1
+++ b/usr.bin/top/top.1
@@ -147,7 +147,7 @@ no information is available about the percentage of time spent by the CPU in eve
 .It Fl s Ar time
 Set the delay between screen updates to
 .Ar time
-seconds.
+seconds, which may be fractional.
 The default delay between updates is 1 second.
 .It Fl o Ar field
 Sort the process display area on the specified field.
diff --git a/usr.bin/top/top.c b/usr.bin/top/top.c
index 01cad421b64c..cd357a092e9f 100644
--- a/usr.bin/top/top.c
+++ b/usr.bin/top/top.c
@@ -233,7 +233,7 @@ main(int argc, const char *argv[])
     static char tempbuf2[50];
 	sigset_t old_sigmask, new_sigmask;
     int topn = Infinity;
-    double delay = 2;
+    struct timeval delay = { 2, 0 };
     int displays = 0;		/* indicates unspecified */
     int sel_ret = 0;
     time_t curr_time;
@@ -377,20 +377,26 @@ main(int argc, const char *argv[])
 		break;
 	      }
 
-		  case 's':
-			delay = strtod(optarg, &nptr);
-			if (nptr == optarg) {
-				warnx("warning: invalid delay");
-				delay = 2;
-				warnings++;
-			}
-			if (delay < 0) {
-				warnx("warning: seconds delay should be positive -- using default");
-				delay = 2;
-				warnings++;
-			}
-
-		break;
+	      case 's':
+	      {
+		  double delay_d = strtod(optarg, &nptr);
+		  if (nptr == optarg)
+		  {
+		      warnx("warning: invalid delay");
+		      warnings++;
+		  }
+		  else if (delay_d <= 0)
+		  {
+		      warnx("warning: seconds delay should be positive -- using default");
+		      warnings++;
+		  }
+		  else
+		  {
+		      delay.tv_sec = delay_d;
+		      delay.tv_usec = (delay_d - delay.tv_sec) * 1e6;
+		  }
+		  break;
+	      }
 
 	      case 'q':		/* be quick about it */
 			errno = 0;
@@ -704,7 +710,8 @@ restart:
 	    no_command = true;
 	    if (!interactive)
 	    {
-		usleep(delay * 1e6);
+		timeout = delay;
+		select(0, NULL, NULL, NULL, &timeout);
 		if (leaveflag) {
 		    end_screen();
 		    exit(0);
@@ -718,8 +725,7 @@ restart:
 		/* set up arguments for select with timeout */
 		FD_ZERO(&readfds);
 		FD_SET(0, &readfds);		/* for standard input */
-		timeout.tv_sec  = delay;
-		timeout.tv_usec = 0;
+		timeout = delay;
 
 		if (leaveflag) {
 		    end_screen();
@@ -880,12 +886,10 @@ restart:
 
 			    case CMD_delay:	/* new seconds delay */
 				new_message(MT_standout, "Seconds to delay: ");
-				if ((i = readline(tempbuf1, 8, true)) > -1)
+				if ((i = readline(tempbuf1, 8, true)) > 0)
 				{
-				    if ((delay = i) == 0)
-				    {
-					delay = 1;
-				    }
+				    delay.tv_sec = i;
+				    delay.tv_usec = 0;
 				}
 				clear_message();
 				break;