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[14/19] tools/power turbostat: read from pipes too

Message ID c026c23629b825100fd4b8223227d9a395f9a56b.1567277326.git.len.brown@intel.com (mailing list archive)
State Not Applicable, archived
Headers show
Series [01/19] tools/power x86_energy_perf_policy: Fix "uninitialized variable" warnings at -O2 | expand

Commit Message

Len Brown Aug. 31, 2019, 7:34 p.m. UTC 
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

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 reason why this should works for terminals, but not for
pipes. This patch improves the situation. Instead of ignoring pipes, we
read data from them but gracefully handle the EOF case.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
---
 tools/power/x86/turbostat/turbostat.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 393509655449..095bd52cc086 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;
 
 #define RAPL_PKG		(1 << 0)
 					/* 0x610 MSR_PKG_POWER_LIMIT */
@@ -3013,26 +3014,37 @@  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 on the other end. There
+			 * won't be any further input.
+			 */
+			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);