[PATCH v2 0/8] Fix -Wunused-result warnings by checking return values

[PATCH v2 0/8] Fix -Wunused-result warnings by checking return values

[Cheng-Yang Chou]

This v2 series adds proper commit messages and addresses coding style
warnings previously reported by checkpatch.pl.

All patches have been verified with checkpatch.pl and show no errors
or warnings.

Changes in v2:
 - Add commit messages to all patches
 - Ensure all patches pass checkpatch cleanly
 - Link to v1: https://lore.kernel.org/all/20250712134213.58582-1-yphbchou0911@gmail.com/

Thanks,
-chengyang

---

Cheng-Yang Chou (8):
  rt-utils.c: Check return values of write()
  pmqtest.c: Check return values of write() and ftruncate()
  ptsematest.c: Check return values of write() and ftruncate()
  rt-migrate-test.c: Check return values of write() and ftruncate()
  cyclicdeadline.c: Check return values of write() and ftruncate()
  deadline_test.c: Check return values of write() and ftruncate()
  sigwaittest.c: Check return values of write() and ftruncate()
  svsematest.c: Check return values of write() and ftruncate()

 src/lib/rt-utils.c                    |  9 +++++--
 src/pmqtest/pmqtest.c                 |  6 ++++-
 src/ptsematest/ptsematest.c           |  6 ++++-
 src/rt-migrate-test/rt-migrate-test.c |  5 +++-
 src/sched_deadline/cyclicdeadline.c   | 32 +++++++++++++++++++----
 src/sched_deadline/deadline_test.c    | 37 +++++++++++++++++++++++----
 src/sigwaittest/sigwaittest.c         | 13 ++++++++--
 src/svsematest/svsematest.c           | 13 ++++++++--
 8 files changed, 102 insertions(+), 19 deletions(-)

-- 
2.48.1

[PATCH v2 1/8] rt-utils.c: Check return values of write()

[Cheng-Yang Chou]

Add error handling for write() to tracefs in tracemark() to avoid ignoring
partial or failed writes.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/lib/rt-utils.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/lib/rt-utils.c b/src/lib/rt-utils.c
index 6bbd25a..447e158 100644
--- a/src/lib/rt-utils.c
+++ b/src/lib/rt-utils.c
@@ -465,6 +465,7 @@ void tracemark(char *fmt, ...)
 {
 	va_list ap;
 	int len;
+	int ret;
 
 	/* bail out if we're not tracing */
 	/* or if the kernel doesn't support trace_mark */
@@ -476,10 +477,14 @@ void tracemark(char *fmt, ...)
 	va_end(ap);
 
 	/* write the tracemark message */
-	write(tracemark_fd, tracebuf, len);
+	ret = write(tracemark_fd, tracebuf, len);
+	if (ret != len)
+		warn("%s: write failed", __func__);
 
 	/* now stop any trace */
-	write(trace_fd, "0\n", 2);
+	ret = write(trace_fd, "0\n", 2);
+	if (ret != 2)
+		warn("trace stop write failed");
 }
 
 void enable_trace_mark(void)
-- 
2.48.1

Re: [PATCH v2 1/8] rt-utils.c: Check return values of write()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs in tracemark() to avoid ignoring
> partial or failed writes.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/lib/rt-utils.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/src/lib/rt-utils.c b/src/lib/rt-utils.c
> index 6bbd25a..447e158 100644
> --- a/src/lib/rt-utils.c
> +++ b/src/lib/rt-utils.c
> @@ -465,6 +465,7 @@ void tracemark(char *fmt, ...)
>  {
>  	va_list ap;
>  	int len;
> +	int ret;
>  
>  	/* bail out if we're not tracing */
>  	/* or if the kernel doesn't support trace_mark */
> @@ -476,10 +477,14 @@ void tracemark(char *fmt, ...)
>  	va_end(ap);
>  
>  	/* write the tracemark message */
> -	write(tracemark_fd, tracebuf, len);
> +	ret = write(tracemark_fd, tracebuf, len);
> +	if (ret != len)
> +		warn("%s: write failed", __func__);
>  
>  	/* now stop any trace */
> -	write(trace_fd, "0\n", 2);
> +	ret = write(trace_fd, "0\n", 2);
> +	if (ret != 2)
> +		warn("trace stop write failed");
>  }
>  
>  void enable_trace_mark(void)
> -- 
    - resolved merge conflict because an earlier patch changed tracemark()
      and tracing_stop() since this was submitted
    Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 2/8] pmqtest.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs and ftruncate() on shared memory
to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/pmqtest/pmqtest.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/pmqtest/pmqtest.c b/src/pmqtest/pmqtest.c
index 04e36a1..eb20baa 100644
--- a/src/pmqtest/pmqtest.c
+++ b/src/pmqtest/pmqtest.c
@@ -75,6 +75,7 @@ void *pmqthread(void *param)
 	int policy = SCHED_FIFO;
 	struct sched_param schedp;
 	struct timespec ts;
+	int ret;
 
 	memset(&schedp, 0, sizeof(schedp));
 	schedp.sched_priority = par->priority;
@@ -189,7 +190,10 @@ void *pmqthread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					ret = write(tracing_enabled, "0", 1);
+					if (ret < 0)
+						fatal("Could not write to %s: %s\n",
+						      tracing_enabled_file, strerror(errno));
 					close(tracing_enabled);
 				} else
 					fatal("Could not access %s\n", tracing_enabled_file);
-- 
2.48.1

Re: [PATCH v2 2/8] pmqtest.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs and ftruncate() on shared memory
> to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/pmqtest/pmqtest.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/pmqtest/pmqtest.c b/src/pmqtest/pmqtest.c
> index 04e36a1..eb20baa 100644
> --- a/src/pmqtest/pmqtest.c
> +++ b/src/pmqtest/pmqtest.c
> @@ -75,6 +75,7 @@ void *pmqthread(void *param)
>  	int policy = SCHED_FIFO;
>  	struct sched_param schedp;
>  	struct timespec ts;
> +	int ret;
>  
>  	memset(&schedp, 0, sizeof(schedp));
>  	schedp.sched_priority = par->priority;
> @@ -189,7 +190,10 @@ void *pmqthread(void *param)
>  				int tracing_enabled =
>  				    open(tracing_enabled_file, O_WRONLY);
>  				if (tracing_enabled >= 0) {
> -					write(tracing_enabled, "0", 1);
> +					ret = write(tracing_enabled, "0", 1);
> +					if (ret < 0)
> +						fatal("Could not write to %s: %s\n",
> +						      tracing_enabled_file, strerror(errno));
>  					close(tracing_enabled);
>  				} else
>  					fatal("Could not access %s\n", tracing_enabled_file);
> -- 
> 2.48.1
> 
> 
> 
Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 3/8] ptsematest.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs and ftruncate() on shared memory
to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/ptsematest/ptsematest.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/ptsematest/ptsematest.c b/src/ptsematest/ptsematest.c
index d211669..787909c 100644
--- a/src/ptsematest/ptsematest.c
+++ b/src/ptsematest/ptsematest.c
@@ -62,6 +62,7 @@ void *semathread(void *param)
 	cpu_set_t mask;
 	int policy = SCHED_FIFO;
 	struct sched_param schedp;
+	int ret;
 
 	memset(&schedp, 0, sizeof(schedp));
 	schedp.sched_priority = par->priority;
@@ -112,7 +113,10 @@ void *semathread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					ret = write(tracing_enabled, "0", 1);
+					if (ret < 0)
+						fatal("Could not write to %s: %s\n",
+						      tracing_enabled_file, strerror(errno));
 					close(tracing_enabled);
 				} else
 					fatal("Could not access %s\n",
-- 
2.48.1

Re: [PATCH v2 3/8] ptsematest.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs and ftruncate() on shared memory
> to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/ptsematest/ptsematest.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/ptsematest/ptsematest.c b/src/ptsematest/ptsematest.c
> index d211669..787909c 100644
> --- a/src/ptsematest/ptsematest.c
> +++ b/src/ptsematest/ptsematest.c
> @@ -62,6 +62,7 @@ void *semathread(void *param)
>  	cpu_set_t mask;
>  	int policy = SCHED_FIFO;
>  	struct sched_param schedp;
> +	int ret;
>  
>  	memset(&schedp, 0, sizeof(schedp));
>  	schedp.sched_priority = par->priority;
> @@ -112,7 +113,10 @@ void *semathread(void *param)
>  				int tracing_enabled =
>  				    open(tracing_enabled_file, O_WRONLY);
>  				if (tracing_enabled >= 0) {
> -					write(tracing_enabled, "0", 1);
> +					ret = write(tracing_enabled, "0", 1);
> +					if (ret < 0)
> +						fatal("Could not write to %s: %s\n",
> +						      tracing_enabled_file, strerror(errno));
>  					close(tracing_enabled);
>  				} else
>  					fatal("Could not access %s\n",
> -- 
Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 4/8] rt-migrate-test.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs and ftruncate() on shared memory
to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/rt-migrate-test/rt-migrate-test.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/rt-migrate-test/rt-migrate-test.c b/src/rt-migrate-test/rt-migrate-test.c
index 8afe083..e007ed7 100644
--- a/src/rt-migrate-test/rt-migrate-test.c
+++ b/src/rt-migrate-test/rt-migrate-test.c
@@ -61,6 +61,7 @@ static void ftrace_write(const char *fmt, ...)
 {
 	va_list ap;
 	int n;
+	int ret;
 
 	if (mark_fd < 0)
 		return;
@@ -69,7 +70,9 @@ static void ftrace_write(const char *fmt, ...)
 	n = vsnprintf(buff, BUFSIZ, fmt, ap);
 	va_end(ap);
 
-	write(mark_fd, buff, n);
+	ret = write(mark_fd, buff, n);
+	if (ret < 0)
+		fprintf(stderr, "%s: write failed\n", __func__);
 }
 
 #define nano2sec(nan) (nan / 1000000000ULL)
-- 
2.48.1

Re: [PATCH v2 4/8] rt-migrate-test.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs and ftruncate() on shared memory
> to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/rt-migrate-test/rt-migrate-test.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/rt-migrate-test/rt-migrate-test.c b/src/rt-migrate-test/rt-migrate-test.c
> index 8afe083..e007ed7 100644
> --- a/src/rt-migrate-test/rt-migrate-test.c
> +++ b/src/rt-migrate-test/rt-migrate-test.c
> @@ -61,6 +61,7 @@ static void ftrace_write(const char *fmt, ...)
>  {
>  	va_list ap;
>  	int n;
> +	int ret;
>  
>  	if (mark_fd < 0)
>  		return;
> @@ -69,7 +70,9 @@ static void ftrace_write(const char *fmt, ...)
>  	n = vsnprintf(buff, BUFSIZ, fmt, ap);
>  	va_end(ap);
>  
> -	write(mark_fd, buff, n);
> +	ret = write(mark_fd, buff, n);
> +	if (ret < 0)
> +		fprintf(stderr, "%s: write failed\n", __func__);
>  }
>  
>  #define nano2sec(nan) (nan / 1000000000ULL)
> -- 

Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 5/8] cyclicdeadline.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs, cpuset control files, and
system() calls to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/sched_deadline/cyclicdeadline.c | 32 ++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/sched_deadline/cyclicdeadline.c b/src/sched_deadline/cyclicdeadline.c
index 04e61ed..6b5d3e0 100644
--- a/src/sched_deadline/cyclicdeadline.c
+++ b/src/sched_deadline/cyclicdeadline.c
@@ -206,6 +206,7 @@ static void ftrace_write(char *buf, const char *fmt, ...)
 {
 	va_list ap;
 	int n;
+	int ret;
 
 	if (mark_fd < 0)
 		return;
@@ -214,7 +215,9 @@ static void ftrace_write(char *buf, const char *fmt, ...)
 	n = my_vsprintf(buf, BUFSIZ, fmt, ap);
 	va_end(ap);
 
-	write(mark_fd, buf, n);
+	ret = write(mark_fd, buf, n);
+	if (ret < 0)
+		perror("ftrace write failed");
 }
 
 static void setup_ftrace_marker(void)
@@ -448,6 +451,10 @@ static int mount_cpuset(void)
 	if (fd < 0)
 		return fd;
 	ret = write(fd, "0", 2);
+	if (ret < 0) {
+		close(fd);
+		return ret;
+	}
 	close(fd);
 
 	return 0;
@@ -634,7 +641,14 @@ static void destroy_cpuset(const char *name, int print)
 		sprintf(buf, "%d", pid);
 		if (print)
 			printf("Moving %d out of %s\n", pid, name);
-		write(fd, buf, strlen(buf));
+		ret = write(fd, buf, strlen(buf));
+		if (ret < 0 && errno == ENOSPC) {
+			fclose(fp);
+			close(fd);
+			fatal("Cannot move tasks out of cpuset %s\n", name);
+		}
+
+
 	}
 	fclose(fp);
 	close(fd);
@@ -656,19 +670,24 @@ static void destroy_cpuset(const char *name, int print)
 static void teardown(void)
 {
 	int fd;
+	int ret;
 
 	if (all_cpus)
 		return;
 
 	fd = open_cpuset(CPUSET_PATH, "cpuset.cpu_exclusive");
 	if (fd >= 0) {
-		write(fd, "0", 2);
+		ret = write(fd, "0", 2);
+		if (ret < 0)
+			perror("cpuset.cpu_exclusive");
 		close(fd);
 	}
 
 	fd = open_cpuset(CPUSET_PATH, "cpuset.sched_load_balance");
 	if (fd >= 0) {
-		write(fd, "1", 2);
+		ret = write(fd, "1", 2);
+		if (ret < 0)
+			perror("cpuset.sched_load_balance");
 		close(fd);
 	}
 
@@ -1164,6 +1183,7 @@ int main(int argc, char **argv)
 	int nr_cpus;
 	int i;
 	int c;
+	int ret;
 
 	rt_init(argc, argv);
 
@@ -1387,7 +1407,9 @@ int main(int argc, char **argv)
 				  CPUSET_FL_CLONE_CHILDREN |
 				  CPUSET_FL_TASKS, pids);
 
-		system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
+		ret = system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
+		if (ret < 0)
+			perror("system call failed");
 	}
 
 	debug(debug_enable, "main thread %d\n", gettid());
-- 
2.48.1

Re: [PATCH v2 5/8] cyclicdeadline.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs, cpuset control files, and
> system() calls to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/sched_deadline/cyclicdeadline.c | 32 ++++++++++++++++++++++++-----
>  1 file changed, 27 insertions(+), 5 deletions(-)
> 
> diff --git a/src/sched_deadline/cyclicdeadline.c b/src/sched_deadline/cyclicdeadline.c
> index 04e61ed..6b5d3e0 100644
> --- a/src/sched_deadline/cyclicdeadline.c
> +++ b/src/sched_deadline/cyclicdeadline.c
> @@ -206,6 +206,7 @@ static void ftrace_write(char *buf, const char *fmt, ...)
>  {
>  	va_list ap;
>  	int n;
> +	int ret;
>  
>  	if (mark_fd < 0)
>  		return;
> @@ -214,7 +215,9 @@ static void ftrace_write(char *buf, const char *fmt, ...)
>  	n = my_vsprintf(buf, BUFSIZ, fmt, ap);
>  	va_end(ap);
>  
> -	write(mark_fd, buf, n);
> +	ret = write(mark_fd, buf, n);
> +	if (ret < 0)
> +		perror("ftrace write failed");
>  }
>  
>  static void setup_ftrace_marker(void)
> @@ -448,6 +451,10 @@ static int mount_cpuset(void)
>  	if (fd < 0)
>  		return fd;
>  	ret = write(fd, "0", 2);
> +	if (ret < 0) {
> +		close(fd);
> +		return ret;
> +	}
>  	close(fd);
>  
>  	return 0;
> @@ -634,7 +641,14 @@ static void destroy_cpuset(const char *name, int print)
>  		sprintf(buf, "%d", pid);
>  		if (print)
>  			printf("Moving %d out of %s\n", pid, name);
> -		write(fd, buf, strlen(buf));
> +		ret = write(fd, buf, strlen(buf));
> +		if (ret < 0 && errno == ENOSPC) {
> +			fclose(fp);
> +			close(fd);
> +			fatal("Cannot move tasks out of cpuset %s\n", name);
> +		}
> +
> +
>  	}
>  	fclose(fp);
>  	close(fd);
> @@ -656,19 +670,24 @@ static void destroy_cpuset(const char *name, int print)
>  static void teardown(void)
>  {
>  	int fd;
> +	int ret;
>  
>  	if (all_cpus)
>  		return;
>  
>  	fd = open_cpuset(CPUSET_PATH, "cpuset.cpu_exclusive");
>  	if (fd >= 0) {
> -		write(fd, "0", 2);
> +		ret = write(fd, "0", 2);
> +		if (ret < 0)
> +			perror("cpuset.cpu_exclusive");
>  		close(fd);
>  	}
>  
>  	fd = open_cpuset(CPUSET_PATH, "cpuset.sched_load_balance");
>  	if (fd >= 0) {
> -		write(fd, "1", 2);
> +		ret = write(fd, "1", 2);
> +		if (ret < 0)
> +			perror("cpuset.sched_load_balance");
>  		close(fd);
>  	}
>  
> @@ -1164,6 +1183,7 @@ int main(int argc, char **argv)
>  	int nr_cpus;
>  	int i;
>  	int c;
> +	int ret;
>  
>  	rt_init(argc, argv);
>  
> @@ -1387,7 +1407,9 @@ int main(int argc, char **argv)
>  				  CPUSET_FL_CLONE_CHILDREN |
>  				  CPUSET_FL_TASKS, pids);
>  
> -		system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
> +		ret = system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
> +		if (ret < 0)
> +			perror("system call failed");
>  	}
>  
>  	debug(debug_enable, "main thread %d\n", gettid());
> -- 
> 2.48.1
> 
> 
> 
    - Fixed merge conflict due to bd5967b42597 which removed 
ftrace_write()
    Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 6/8] deadline_test.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs, cpuset control files, and
system() calls to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/sched_deadline/deadline_test.c | 37 ++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/sched_deadline/deadline_test.c b/src/sched_deadline/deadline_test.c
index ca2da47..a74d514 100644
--- a/src/sched_deadline/deadline_test.c
+++ b/src/sched_deadline/deadline_test.c
@@ -325,6 +325,7 @@ static void ftrace_write(char *buf, const char *fmt, ...)
 {
 	va_list ap;
 	int n;
+	int ret;
 
 	if (mark_fd < 0)
 		return;
@@ -333,7 +334,9 @@ static void ftrace_write(char *buf, const char *fmt, ...)
 	n = my_vsprintf(buf, BUFSIZ, fmt, ap);
 	va_end(ap);
 
-	write(mark_fd, buf, n);
+	ret = write(mark_fd, buf, n);
+	if (ret < 0)
+		perror("ftrace write failed");
 }
 
 /**
@@ -626,6 +629,10 @@ static int mount_cpuset(void)
 	if (fd < 0)
 		return fd;
 	ret = write(fd, "0", 2);
+	if (ret < 0) {
+		close(fd);
+		return ret;
+	}
 	close(fd);
 
 	return 0;
@@ -875,7 +882,19 @@ static void destroy_cpuset(const char *name, int print)
 		sprintf(buf, "%d", pid);
 		if (print)
 			printf("Moving %d out of %s\n", pid, name);
-		write(fd, buf, strlen(buf));
+		ret = write(fd, buf, strlen(buf));
+		if (ret < 0 && errno == ENOSPC) {
+			/*
+			 * If we get ENOSPC, then we have a problem, as it
+			 * means that the cpuset is full, and we cannot move
+			 * the tasks out of it.
+			 */
+			fclose(fp);
+			close(fd);
+			fprintf(stderr, "Failed to move %d out of %s\n", pid, name);
+			perror("write");
+			return;
+		}
 	}
 	fclose(fp);
 	close(fd);
@@ -910,16 +929,21 @@ static void destroy_cpuset(const char *name, int print)
 static void teardown(void)
 {
 	int fd;
+	int ret;
 
 	fd = open_cpuset(CPUSET_PATH, "cpuset.cpu_exclusive");
 	if (fd >= 0) {
-		write(fd, "0", 2);
+		ret = write(fd, "0", 2);
+		if (ret < 0)
+			perror("cpuset.cpu_exclusive");
 		close(fd);
 	}
 
 	fd = open_cpuset(CPUSET_PATH, "cpuset.sched_load_balance");
 	if (fd >= 0) {
-		write(fd, "1", 2);
+		ret = write(fd, "1", 2);
+		if (ret < 0)
+			perror("cpuset.sched_load_balance");
 		close(fd);
 	}
 
@@ -1790,6 +1814,7 @@ int main(int argc, char **argv)
 	int rt_task = 0;
 	int i;
 	int c;
+	int ret;
 
 	cpu_count = sysconf(_SC_NPROCESSORS_CONF);
 	if (cpu_count < 1) {
@@ -2041,7 +2066,9 @@ int main(int argc, char **argv)
 			exit(-1);
 		}
 
-		system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
+		ret = system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
+		if (ret < 0)
+			perror("system call failed");
 	}
 
 	pthread_barrier_wait(&barrier);
-- 
2.48.1

Re: [PATCH v2 6/8] deadline_test.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs, cpuset control files, and
> system() calls to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/sched_deadline/deadline_test.c | 37 ++++++++++++++++++++++++++----
>  1 file changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/src/sched_deadline/deadline_test.c b/src/sched_deadline/deadline_test.c
> index ca2da47..a74d514 100644
> --- a/src/sched_deadline/deadline_test.c
> +++ b/src/sched_deadline/deadline_test.c
> @@ -325,6 +325,7 @@ static void ftrace_write(char *buf, const char *fmt, ...)
>  {
>  	va_list ap;
>  	int n;
> +	int ret;
>  
>  	if (mark_fd < 0)
>  		return;
> @@ -333,7 +334,9 @@ static void ftrace_write(char *buf, const char *fmt, ...)
>  	n = my_vsprintf(buf, BUFSIZ, fmt, ap);
>  	va_end(ap);
>  
> -	write(mark_fd, buf, n);
> +	ret = write(mark_fd, buf, n);
> +	if (ret < 0)
> +		perror("ftrace write failed");
>  }
>  
>  /**
> @@ -626,6 +629,10 @@ static int mount_cpuset(void)
>  	if (fd < 0)
>  		return fd;
>  	ret = write(fd, "0", 2);
> +	if (ret < 0) {
> +		close(fd);
> +		return ret;
> +	}
>  	close(fd);
>  
>  	return 0;
> @@ -875,7 +882,19 @@ static void destroy_cpuset(const char *name, int print)
>  		sprintf(buf, "%d", pid);
>  		if (print)
>  			printf("Moving %d out of %s\n", pid, name);
> -		write(fd, buf, strlen(buf));
> +		ret = write(fd, buf, strlen(buf));
> +		if (ret < 0 && errno == ENOSPC) {
> +			/*
> +			 * If we get ENOSPC, then we have a problem, as it
> +			 * means that the cpuset is full, and we cannot move
> +			 * the tasks out of it.
> +			 */
> +			fclose(fp);
> +			close(fd);
> +			fprintf(stderr, "Failed to move %d out of %s\n", pid, name);
> +			perror("write");
> +			return;
> +		}
>  	}
>  	fclose(fp);
>  	close(fd);
> @@ -910,16 +929,21 @@ static void destroy_cpuset(const char *name, int print)
>  static void teardown(void)
>  {
>  	int fd;
> +	int ret;
>  
>  	fd = open_cpuset(CPUSET_PATH, "cpuset.cpu_exclusive");
>  	if (fd >= 0) {
> -		write(fd, "0", 2);
> +		ret = write(fd, "0", 2);
> +		if (ret < 0)
> +			perror("cpuset.cpu_exclusive");
>  		close(fd);
>  	}
>  
>  	fd = open_cpuset(CPUSET_PATH, "cpuset.sched_load_balance");
>  	if (fd >= 0) {
> -		write(fd, "1", 2);
> +		ret = write(fd, "1", 2);
> +		if (ret < 0)
> +			perror("cpuset.sched_load_balance");
>  		close(fd);
>  	}
>  
> @@ -1790,6 +1814,7 @@ int main(int argc, char **argv)
>  	int rt_task = 0;
>  	int i;
>  	int c;
> +	int ret;
>  
>  	cpu_count = sysconf(_SC_NPROCESSORS_CONF);
>  	if (cpu_count < 1) {
> @@ -2041,7 +2066,9 @@ int main(int argc, char **argv)
>  			exit(-1);
>  		}
>  
> -		system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
> +		ret = system("cat /sys/fs/cgroup/cpuset/my_cpuset/tasks");
> +		if (ret < 0)
> +			perror("system call failed");
>  	}
>  
>  	pthread_barrier_wait(&barrier);
> -- 
> 2.48.1
> 
> 
> 
Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 7/8] sigwaittest.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs and ftruncate() on shared memory
to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/sigwaittest/sigwaittest.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/sigwaittest/sigwaittest.c b/src/sigwaittest/sigwaittest.c
index 026cc81..3944b54 100644
--- a/src/sigwaittest/sigwaittest.c
+++ b/src/sigwaittest/sigwaittest.c
@@ -72,6 +72,7 @@ void *semathread(void *param)
 	cpu_set_t mask;
 	int policy = SCHED_FIFO;
 	struct sched_param schedp;
+	int ret;
 
 	memset(&schedp, 0, sizeof(schedp));
 	schedp.sched_priority = par->priority;
@@ -168,7 +169,10 @@ void *semathread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					ret = write(tracing_enabled, "0", 1);
+					if (ret < 0)
+						fatal("Could not write to %s: %s\n",
+						      tracing_enabled_file, strerror(errno));
 					close(tracing_enabled);
 				} else
 					fatal("Could not access %s\n",
@@ -489,7 +493,12 @@ int main(int argc, char *argv[])
 			fprintf(stderr, "Could not create shared memory\n");
 			return 1;
 		}
-		ftruncate(shmem, totalsize);
+		if (ftruncate(shmem, totalsize) == -1) {
+			perror("ftruncate failed");
+			close(shmem);
+			shm_unlink("/sigwaittest");
+			return 1;
+		}
 		param = mmap(0, totalsize, PROT_READ|PROT_WRITE, MAP_SHARED,
 		    shmem, 0);
 		if (param == MAP_FAILED) {
-- 
2.48.1

Re: [PATCH v2 7/8] sigwaittest.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs and ftruncate() on shared memory
> to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/sigwaittest/sigwaittest.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/src/sigwaittest/sigwaittest.c b/src/sigwaittest/sigwaittest.c
> index 026cc81..3944b54 100644
> --- a/src/sigwaittest/sigwaittest.c
> +++ b/src/sigwaittest/sigwaittest.c
> @@ -72,6 +72,7 @@ void *semathread(void *param)
>  	cpu_set_t mask;
>  	int policy = SCHED_FIFO;
>  	struct sched_param schedp;
> +	int ret;
>  
>  	memset(&schedp, 0, sizeof(schedp));
>  	schedp.sched_priority = par->priority;
> @@ -168,7 +169,10 @@ void *semathread(void *param)
>  				int tracing_enabled =
>  				    open(tracing_enabled_file, O_WRONLY);
>  				if (tracing_enabled >= 0) {
> -					write(tracing_enabled, "0", 1);
> +					ret = write(tracing_enabled, "0", 1);
> +					if (ret < 0)
> +						fatal("Could not write to %s: %s\n",
> +						      tracing_enabled_file, strerror(errno));
>  					close(tracing_enabled);
>  				} else
>  					fatal("Could not access %s\n",
> @@ -489,7 +493,12 @@ int main(int argc, char *argv[])
>  			fprintf(stderr, "Could not create shared memory\n");
>  			return 1;
>  		}
> -		ftruncate(shmem, totalsize);
> +		if (ftruncate(shmem, totalsize) == -1) {
> +			perror("ftruncate failed");
> +			close(shmem);
> +			shm_unlink("/sigwaittest");
> +			return 1;
> +		}
>  		param = mmap(0, totalsize, PROT_READ|PROT_WRITE, MAP_SHARED,
>  		    shmem, 0);
>  		if (param == MAP_FAILED) {
> -- 
> 2.48.1
> 
> 
> 
Signed-off-by: John Kacur <jkacur@redhat.com>

[PATCH v2 8/8] svsematest.c: Check return values of write() and ftruncate()

[Cheng-Yang Chou]

Add error handling for write() to tracefs and ftruncate() on shared memory
to avoid ignoring errors.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 src/svsematest/svsematest.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/svsematest/svsematest.c b/src/svsematest/svsematest.c
index f3cddf8..bdc82bc 100644
--- a/src/svsematest/svsematest.c
+++ b/src/svsematest/svsematest.c
@@ -84,6 +84,7 @@ void *semathread(void *param)
 	struct sched_param schedp;
 	struct sembuf sb = { 0, 0, 0};
 	sigset_t sigset;
+	int ret;
 
 	sigemptyset(&sigset);
 	pthread_sigmask(SIG_SETMASK, &sigset, NULL);
@@ -175,7 +176,10 @@ void *semathread(void *param)
 				int tracing_enabled =
 				    open(tracing_enabled_file, O_WRONLY);
 				if (tracing_enabled >= 0) {
-					write(tracing_enabled, "0", 1);
+					ret = write(tracing_enabled, "0", 1);
+					if (ret < 0)
+						fatal("Could not write to %s: %s\n",
+						      tracing_enabled_file, strerror(errno));
 					close(tracing_enabled);
 				} else
 					fatal("Could not access %s\n",
@@ -544,7 +548,12 @@ int main(int argc, char *argv[])
 			fprintf(stderr, "Could not create shared memory\n");
 			return 1;
 		}
-		ftruncate(shmem, totalsize);
+		if (ftruncate(shmem, totalsize) == -1) {
+			perror("ftruncate failed");
+			close(shmem);
+			shm_unlink("/sigwaittest");
+			return 1;
+		}
 		param = mmap(0, totalsize, PROT_READ|PROT_WRITE, MAP_SHARED,
 		    shmem, 0);
 		if (param == MAP_FAILED) {
-- 
2.48.1

Re: [PATCH v2 8/8] svsematest.c: Check return values of write() and ftruncate()

[John Kacur]

On Sat, 26 Jul 2025, Cheng-Yang Chou wrote:

> Add error handling for write() to tracefs and ftruncate() on shared memory
> to avoid ignoring errors.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  src/svsematest/svsematest.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/src/svsematest/svsematest.c b/src/svsematest/svsematest.c
> index f3cddf8..bdc82bc 100644
> --- a/src/svsematest/svsematest.c
> +++ b/src/svsematest/svsematest.c
> @@ -84,6 +84,7 @@ void *semathread(void *param)
>  	struct sched_param schedp;
>  	struct sembuf sb = { 0, 0, 0};
>  	sigset_t sigset;
> +	int ret;
>  
>  	sigemptyset(&sigset);
>  	pthread_sigmask(SIG_SETMASK, &sigset, NULL);
> @@ -175,7 +176,10 @@ void *semathread(void *param)
>  				int tracing_enabled =
>  				    open(tracing_enabled_file, O_WRONLY);
>  				if (tracing_enabled >= 0) {
> -					write(tracing_enabled, "0", 1);
> +					ret = write(tracing_enabled, "0", 1);
> +					if (ret < 0)
> +						fatal("Could not write to %s: %s\n",
> +						      tracing_enabled_file, strerror(errno));
>  					close(tracing_enabled);
>  				} else
>  					fatal("Could not access %s\n",
> @@ -544,7 +548,12 @@ int main(int argc, char *argv[])
>  			fprintf(stderr, "Could not create shared memory\n");
>  			return 1;
>  		}
> -		ftruncate(shmem, totalsize);
> +		if (ftruncate(shmem, totalsize) == -1) {
> +			perror("ftruncate failed");
> +			close(shmem);
> +			shm_unlink("/sigwaittest");
> +			return 1;
> +		}
>  		param = mmap(0, totalsize, PROT_READ|PROT_WRITE, MAP_SHARED,
>  		    shmem, 0);
>  		if (param == MAP_FAILED) {
> -- 
> 2.48.1
> 
> 
> 
Signed-off-by: John Kacur <jkacur@redhat.com>

Re: [PATCH v2 0/8] Fix -Wunused-result warnings by checking return values

[Cheng-Yang Chou]

On Sat, Jul 26, 2025 at 05:18:29PM +0800, Cheng-Yang Chou wrote:
> This v2 series adds proper commit messages and addresses coding style
> warnings previously reported by checkpatch.pl.
> 
> All patches have been verified with checkpatch.pl and show no errors
> or warnings.
> 
> Changes in v2:
>  - Add commit messages to all patches
>  - Ensure all patches pass checkpatch cleanly
>  - Link to v1: https://lore.kernel.org/all/20250712134213.58582-1-yphbchou0911@gmail.com/

Hi Clark and John,

Gentle ping.

Thanks
-chengyang

Re: [PATCH v2 0/8] Fix -Wunused-result warnings by checking return values

[Cheng-Yang Chou]

On Fri, Aug 08, 2025 at 12:26:03AM +0800, Cheng-Yang Chou wrote:
> On Sat, Jul 26, 2025 at 05:18:29PM +0800, Cheng-Yang Chou wrote:
> > This v2 series adds proper commit messages and addresses coding style
> > warnings previously reported by checkpatch.pl.
> > 
> > All patches have been verified with checkpatch.pl and show no errors
> > or warnings.
> > 
> > Changes in v2:
> >  - Add commit messages to all patches
> >  - Ensure all patches pass checkpatch cleanly
> >  - Link to v1: https://lore.kernel.org/all/20250712134213.58582-1-yphbchou0911@gmail.com/
> 
> Hi Clark and John,
> 
> Gentle ping.

Gentle ping.

Thanks
-chengyang

Re: [PATCH v2 0/8] Fix -Wunused-result warnings by checking return values

[Cheng-Yang Chou]

On Sat, Aug 23, 2025 at 08:40:26PM +0800, Cheng-Yang Chou wrote:
> On Fri, Aug 08, 2025 at 12:26:03AM +0800, Cheng-Yang Chou wrote:
> > On Sat, Jul 26, 2025 at 05:18:29PM +0800, Cheng-Yang Chou wrote:
> > > This v2 series adds proper commit messages and addresses coding style
> > > warnings previously reported by checkpatch.pl.
> > > 
> > > All patches have been verified with checkpatch.pl and show no errors
> > > or warnings.
> > > 
> > > Changes in v2:
> > >  - Add commit messages to all patches
> > >  - Ensure all patches pass checkpatch cleanly
> > >  - Link to v1: https://lore.kernel.org/all/20250712134213.58582-1-yphbchou0911@gmail.com/
> > 
> > Hi Clark and John,
> > 
> > Gentle ping.
> 
> Gentle ping.
> 

Gentle ping.

Thanks
-chengyang