Currently if we encounter an error between fork() and exec() of a child
process we log the error to stderr. This means that the errors don't get
annotated with the child information which makes diagnostics harder and
means that if we miss the exit signal from the child we can deadlock
waiting for output from the child. Improve robustness and output quality
by logging to stdout instead.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/arm64/fp/fp-stress.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/arm64/fp/fp-stress.c b/tools/testing/selftests/arm64/fp/fp-stress.c
index faac24bdefeb9436e2daf20b7250d0ae25ca23a7..80f22789504d661efc52a90d4b0893fbebec42f8 100644
--- a/tools/testing/selftests/arm64/fp/fp-stress.c
+++ b/tools/testing/selftests/arm64/fp/fp-stress.c
@@ -79,7 +79,7 @@ static void child_start(struct child_data *child, const char *program)
 		 */
 		ret = dup2(pipefd[1], 1);
 		if (ret == -1) {
-			fprintf(stderr, "dup2() %d\n", errno);
+			printf("dup2() %d\n", errno);
 			exit(EXIT_FAILURE);
 		}
 
@@ -89,7 +89,7 @@ static void child_start(struct child_data *child, const char *program)
 		 */
 		ret = dup2(startup_pipe[0], 3);
 		if (ret == -1) {
-			fprintf(stderr, "dup2() %d\n", errno);
+			printf("dup2() %d\n", errno);
 			exit(EXIT_FAILURE);
 		}
 
@@ -107,16 +107,15 @@ static void child_start(struct child_data *child, const char *program)
 		 */
 		ret = read(3, &i, sizeof(i));
 		if (ret < 0)
-			fprintf(stderr, "read(startp pipe) failed: %s (%d)\n",
-				strerror(errno), errno);
+			printf("read(startp pipe) failed: %s (%d)\n",
+			       strerror(errno), errno);
 		if (ret > 0)
-			fprintf(stderr, "%d bytes of data on startup pipe\n",
-				ret);
+			printf("%d bytes of data on startup pipe\n", ret);
 		close(3);
 
 		ret = execl(program, program, NULL);
-		fprintf(stderr, "execl(%s) failed: %d (%s)\n",
-			program, errno, strerror(errno));
+		printf("execl(%s) failed: %d (%s)\n",
+		       program, errno, strerror(errno));
 
 		exit(EXIT_FAILURE);
 	} else {

---
base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354
change-id: 20241017-arm64-fp-stress-exec-fail-d074ec82cf43

Best regards,
-- 
Mark Brown <broonie@kernel.org>

On Wed, 23 Oct 2024 00:20:45 +0100, Mark Brown wrote:
> Currently if we encounter an error between fork() and exec() of a child
> process we log the error to stderr. This means that the errors don't get
> annotated with the child information which makes diagnostics harder and
> means that if we miss the exit signal from the child we can deadlock
> waiting for output from the child. Improve robustness and output quality
> by logging to stdout instead.
> 
> [...]

Applied to arm64 (for-next/kselftest), thanks!

[1/1] kselftest/arm64: Log fp-stress child startup errors to stdout
      https://git.kernel.org/arm64/c/dca93d29845d

-- 
Catalin