[1/2] tools/power turbostat: read from pipes too

Commit Message

Artem Bityutskiy Aug. 14, 2019, 5:01 p.m. UTC

From: root <[e-mail]0net>

Commit '47936f944e78 tools/power turbostat: fix printing on input' make
a valid fix, but it completely disabled piped stdin support, which is
a valuable use-case. Indeed, if stdin is a pipe, turbostat won't read
anything from it, so it becomes impossible to get turbostat output at
user-defined moments, instead of the regular intervals.

There is no reson why this should works for terminals, but not for
pipes. This patch imporves the situation. Instead of ignoring pipes, we
read data from them but gracefully handle the EOF case.

Change-Id: Iadf2f17d10bc0d3896bb96a6e466896ec70f2c4c
Signed-off-by: Artem Bityutskiy <[e-mail]>
---
 tools/power/x86/turbostat/turbostat.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

Patch

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 75fc4fb9901c..573230a774cd 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -100,6 +100,7 @@  unsigned int has_hwp_epp;		/* IA32_HWP_REQUEST[bits 31:24] */
 unsigned int has_hwp_pkg;		/* IA32_HWP_REQUEST_PKG */
 unsigned int has_misc_feature_control;
 unsigned int first_counter_read = 1;
+int ignore_stdin = 0;
 
 #define RAPL_PKG		(1 << 0)
 					/* 0x610 MSR_PKG_POWER_LIMIT */
@@ -3005,26 +3006,37 @@  void setup_signal_handler(void)
 
 void do_sleep(void)
 {
-	struct timeval select_timeout;
+	struct timeval tout;
+	struct timespec rest;
 	fd_set readfds;
 	int retval;
 
 	FD_ZERO(&readfds);
 	FD_SET(0, &readfds);
 
-	if (!isatty(fileno(stdin))) {
+	if (ignore_stdin) {
 		nanosleep(&interval_ts, NULL);
 		return;
 	}
 
-	select_timeout = interval_tv;
-	retval = select(1, &readfds, NULL, NULL, &select_timeout);
+	tout = interval_tv;
+	retval = select(1, &readfds, NULL, NULL, &tout);
 
 	if (retval == 1) {
 		switch (getc(stdin)) {
 		case 'q':
 			exit_requested = 1;
 			break;
+		case EOF:
+			/*
+			 * 'stdin' is a pipe closed by the other end. There
+			 * won't be any input in the future.
+			 */
+			ignore_stdin = 1;
+			/* Sleep the rest of the time */
+			rest.tv_sec = (tout.tv_sec + tout.tv_usec / 1000000);
+			rest.tv_nsec = (tout.tv_usec % 1000000) * 1000;
+			nanosleep(&rest, NULL);
 		}
 		/* make sure this manually-invoked interval is at least 1ms long */
 		nanosleep(&one_msec, NULL);