tools/power turbostat: end current interval upon newline input

In turbostat interval mode, a newline typed on standard input
will now conclude the current interval.  Data will immediately
be collected and printed for that interval, and the next interval
will be started.

This is similar to the recently added SIGUSR1 feature.
But that is for use by programs, while this is for interactive use.
Signed-off-by: Len Brown <len.brown@intel.com>

tools/power/x86/turbostat/turbostat.8

@@ -267,6 +267,13 @@ CPU	  PRF_CTRL
 
 .fi
 
+.SH INPUT
+
+For interval-mode, turbostat will immediately end the current interval
+when it sees a newline on standard input.
+turbostat will then start the next interval.
+Control-C will be send a SIGINT to turbostat,
+which will immediately abort the program with no further processing.
 .SH SIGNALS
 
 SIGINT will interrupt interval-mode.

tools/power/x86/turbostat/turbostat.c

@@ -29,6 +29,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/stat.h>
+#include <sys/select.h>
 #include <sys/resource.h>
 #include <fcntl.h>
 #include <signal.h>
@@ -47,7 +48,8 @@
 char *proc_stat = "/proc/stat";
 FILE *outf;
 int *fd_percpu;
-struct timespec interval_ts = {5, 0};
+struct timeval interval_tv = {5, 0};
+struct timespec one_msec = {0, 1000000};
 unsigned int debug;
 unsigned int quiet;
 unsigned int shown;
@@ -478,7 +480,7 @@ void help(void)
 	"--cpu	cpu-set	limit output to summary plus cpu-set:\n"
 	"		{core | package | j,k,l..m,n-p }\n"
 	"--quiet	skip decoding system configuration header\n"
-	"--interval sec	Override default 5-second measurement interval\n"
+	"--interval sec.subsec	Override default 5-second measurement interval\n"
 	"--help		print this help message\n"
 	"--list		list column headers only\n"
 	"--out file	create or truncate \"file\" for all output\n"
@@ -2615,6 +2617,8 @@ static void signal_handler (int signal)
 			fprintf(stderr, "SIGUSR1\n");
 		break;
 	}
+	/* make sure this manually-invoked interval is at least 1ms long */
+	nanosleep(&one_msec, NULL);
 }
 
 void setup_signal_handler(void)
@@ -2630,6 +2634,33 @@ void setup_signal_handler(void)
 	if (sigaction(SIGUSR1, &sa, NULL) < 0)
 		err(1, "sigaction SIGUSR1");
 }
+
+int do_sleep(void)
+{
+	struct timeval select_timeout;
+	fd_set readfds;
+	int retval;
+
+	FD_ZERO(&readfds);
+	FD_SET(0, &readfds);
+
+	select_timeout = interval_tv;
+
+	retval = select(1, &readfds, NULL, NULL, &select_timeout);
+
+	if (retval == 1) {
+
+		switch (getc(stdin)) {
+		case 'q':
+			exit_requested = 1;
+			break;
+		}
+		/* make sure this manually-invoked interval is at least 1ms long */
+		nanosleep(&one_msec, NULL);
+	}
+
+	return retval;
+}
 void turbostat_loop()
 {
 	int retval;
@@ -2659,7 +2690,7 @@ void turbostat_loop()
 			re_initialize();
 			goto restart;
 		}
-		nanosleep(&interval_ts, NULL);
+		do_sleep();
 		if (snapshot_proc_sysfs_files())
 			goto restart;
 		retval = for_all_cpus(get_counters, ODD_COUNTERS);
@@ -2680,7 +2711,7 @@ void turbostat_loop()
 		flush_output_stdout();
 		if (exit_requested)
 			break;
-		nanosleep(&interval_ts, NULL);
+		do_sleep();
 		if (snapshot_proc_sysfs_files())
 			goto restart;
 		retval = for_all_cpus(get_counters, EVEN_COUNTERS);
@@ -5103,8 +5134,8 @@ void cmdline(int argc, char **argv)
 					exit(2);
 				}
 
-				interval_ts.tv_sec = interval;
-				interval_ts.tv_nsec = (interval - interval_ts.tv_sec) * 1000000000;
+				interval_tv.tv_sec = interval;
+				interval_tv.tv_usec = (interval - interval_tv.tv_sec) * 1000000;
 			}
 			break;
 		case 'J':