linux-kernel - [PATCH 2/3] perf kvm: Allow running without stdin

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Message-ID: <1571795693-23558-3-git-send-email-ilubashe@akamai.com>
Date:   Tue, 22 Oct 2019 21:54:52 -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 2/3] perf kvm: Allow running without stdin

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

The following now works as expected:

  $ perf kvm top --stdio < /dev/null

Signed-off-by: Igor Lubashev <ilubashe@...mai.com>
---
 tools/perf/builtin-kvm.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 858da896b518..5217aa3596c7 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -930,18 +930,20 @@ static int fd_set_nonblock(int fd)
 
 static int perf_kvm__handle_stdin(void)
 {
-	int c;
-
-	c = getc(stdin);
-	if (c == 'q')
+	switch (getc(stdin)) {
+	case 'q':
+		done = 1;
 		return 1;
-
-	return 0;
+	case EOF:
+		return 0;
+	default:
+		return 1;
+	}
 }
 
 static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 {
-	int nr_stdin, ret, err = -EINVAL;
+	int nr_stdin = -1, ret, err = -EINVAL;
 	struct termios save;
 
 	/* live flag must be set first */
@@ -972,13 +974,16 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 	if (evlist__add_pollfd(kvm->evlist, kvm->timerfd) < 0)
 		goto out;
 
-	nr_stdin = evlist__add_pollfd(kvm->evlist, fileno(stdin));
-	if (nr_stdin < 0)
-		goto out;
-
 	if (fd_set_nonblock(fileno(stdin)) != 0)
 		goto out;
 
+	/* add stdin, if it is connected */
+	if (getc(stdin) != EOF) {
+		nr_stdin = evlist__add_pollfd(kvm->evlist, fileno(stdin));
+		if (nr_stdin < 0)
+			goto out;
+	}
+
 	/* everything is good - enable the events and process */
 	evlist__enable(kvm->evlist);
 
@@ -994,8 +999,10 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 		if (err)
 			goto out;
 
-		if (fda->entries[nr_stdin].revents & POLLIN)
-			done = perf_kvm__handle_stdin();
+		if (nr_stdin >= 0 && fda->entries[nr_stdin].revents & POLLIN) {
+			if (!perf_kvm__handle_stdin())
+				fda->entries[nr_stdin].events = 0;
+		}
 
 		if (!rc && !done)
 			err = fdarray__poll(fda, 100);
-- 
2.7.4