linux-kernel - [PATCH v1 3/4] perf test: Use a single fd for the child process out/err

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Message-Id: <20240301074639.2260708-3-irogers@google.com>
Date: Thu, 29 Feb 2024 23:46:38 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Christian Brauner <brauner@...nel.org>, James Clark <james.clark@....com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Tim Chen <tim.c.chen@...ux.intel.com>, 
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, Yicong Yang <yangyicong@...ilicon.com>, 
	Kajol Jain <kjain@...ux.ibm.com>, Disha Goel <disgoel@...ux.ibm.com>, 
	K Prateek Nayak <kprateek.nayak@....com>, Song Liu <songliubraving@...com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: [PATCH v1 3/4] perf test: Use a single fd for the child process out/err

Switch from dumping err then out, to a single file descriptor for both
of them. This allows the err and output to be correctly interleaved in
verbose output.

Fixes: b482f5f8e016 ("perf tests: Add option to run tests in parallel")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/tests/builtin-test.c | 37 ++++++---------------------------
 1 file changed, 6 insertions(+), 31 deletions(-)

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index d13ee7683d9d..e05b370b1e2b 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -274,11 +274,8 @@ static int finish_test(struct child_test *child_test, int width)
 	struct test_suite *t = child_test->test;
 	int i = child_test->test_num;
 	int subi = child_test->subtest;
-	int out = child_test->process.out;
 	int err = child_test->process.err;
-	bool out_done = out <= 0;
 	bool err_done = err <= 0;
-	struct strbuf out_output = STRBUF_INIT;
 	struct strbuf err_output = STRBUF_INIT;
 	int ret;
 
@@ -290,11 +287,9 @@ static int finish_test(struct child_test *child_test, int width)
 		pr_info("%3d: %-*s:\n", i + 1, width, test_description(t, -1));
 
 	/*
-	 * Busy loop reading from the child's stdout and stderr that are set to
-	 * be non-blocking until EOF.
+	 * Busy loop reading from the child's stdout/stderr that are set to be
+	 * non-blocking until EOF.
 	 */
-	if (!out_done)
-		fcntl(out, F_SETFL, O_NONBLOCK);
 	if (!err_done)
 		fcntl(err, F_SETFL, O_NONBLOCK);
 	if (verbose > 1) {
@@ -303,11 +298,8 @@ static int finish_test(struct child_test *child_test, int width)
 		else
 			pr_info("%3d: %s:\n", i + 1, test_description(t, -1));
 	}
-	while (!out_done || !err_done) {
-		struct pollfd pfds[2] = {
-			{ .fd = out,
-			  .events = POLLIN | POLLERR | POLLHUP | POLLNVAL,
-			},
+	while (!err_done) {
+		struct pollfd pfds[1] = {
 			{ .fd = err,
 			  .events = POLLIN | POLLERR | POLLHUP | POLLNVAL,
 			},
@@ -317,21 +309,7 @@ static int finish_test(struct child_test *child_test, int width)
 
 		/* Poll to avoid excessive spinning, timeout set for 1000ms. */
 		poll(pfds, ARRAY_SIZE(pfds), /*timeout=*/1000);
-		if (!out_done && pfds[0].revents) {
-			errno = 0;
-			len = read(out, buf, sizeof(buf) - 1);
-
-			if (len <= 0) {
-				out_done = errno != EAGAIN;
-			} else {
-				buf[len] = '\0';
-				if (verbose > 1)
-					fprintf(stdout, "%s", buf);
-				else
-					strbuf_addstr(&out_output, buf);
-			}
-		}
-		if (!err_done && pfds[1].revents) {
+		if (!err_done && pfds[0].revents) {
 			errno = 0;
 			len = read(err, buf, sizeof(buf) - 1);
 
@@ -354,14 +332,10 @@ static int finish_test(struct child_test *child_test, int width)
 			pr_info("%3d.%1d: %s:\n", i + 1, subi + 1, test_description(t, subi));
 		else
 			pr_info("%3d: %s:\n", i + 1, test_description(t, -1));
-		fprintf(stdout, "%s", out_output.buf);
 		fprintf(stderr, "%s", err_output.buf);
 	}
-	strbuf_release(&out_output);
 	strbuf_release(&err_output);
 	print_test_result(t, i, subi, ret, width);
-	if (out > 0)
-		close(out);
 	if (err > 0)
 		close(err);
 	return 0;
@@ -394,6 +368,7 @@ static int start_test(struct test_suite *test, int i, int subi, struct child_tes
 		(*child)->process.no_stdout = 1;
 		(*child)->process.no_stderr = 1;
 	} else {
+		(*child)->process.stdout_to_stderr = 1;
 		(*child)->process.out = -1;
 		(*child)->process.err = -1;
 	}
-- 
2.44.0.278.ge034bb2e1d-goog