linux-kernel - [PATCH 1/3] perf top: Allow running without stdin

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Message-ID: <1571795693-23558-2-git-send-email-ilubashe@akamai.com>
Date:   Tue, 22 Oct 2019 21:54:51 -0400
From:   Igor Lubashev <ilubashe@...mai.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
CC:     Igor Lubashev <ilubashe@...mai.com>, Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/3] perf top: Allow running without stdin

Allow perf top --stdio to run without access to stdin.
This lets perf top to run in a batch mode until interrupted.

The following now works as expected:

  $ perf top < /dev/null

Signed-off-by: Igor Lubashev <ilubashe@...mai.com>
---
 tools/perf/builtin-top.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index d96f24c8770d..fbc0dc135b8a 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -665,6 +665,7 @@ static void display_setup_sig(void)
 static void *display_thread(void *arg)
 {
 	struct pollfd stdin_poll = { .fd = 0, .events = POLLIN };
+	nfds_t nfds = 1;
 	struct termios save;
 	struct perf_top *top = arg;
 	int delay_msecs, c;
@@ -684,7 +685,8 @@ static void *display_thread(void *arg)
 	delay_msecs = top->delay_secs * MSEC_PER_SEC;
 	set_term_quiet_input(&save);
 	/* trash return*/
-	getc(stdin);
+	if (getc(stdin) == EOF)
+		nfds = 0;
 
 	while (!done) {
 		perf_top__print_sym_table(top);
@@ -692,7 +694,7 @@ static void *display_thread(void *arg)
 		 * Either timeout expired or we got an EINTR due to SIGWINCH,
 		 * refresh screen in both cases.
 		 */
-		switch (poll(&stdin_poll, 1, delay_msecs)) {
+		switch (poll(&stdin_poll, nfds, delay_msecs)) {
 		case 0:
 			continue;
 		case -1:
@@ -701,6 +703,10 @@ static void *display_thread(void *arg)
 			__fallthrough;
 		default:
 			c = getc(stdin);
+			if (c == EOF) {
+				nfds = 0;
+				continue;
+			}
 			tcsetattr(0, TCSAFLUSH, &save);
 
 			if (perf_top__handle_keypress(top, c))
-- 
2.7.4