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Subject[PATCH 2/4] samples/bpf: Check the result of system()
Date
To avoid the below build warning message,
use new generate_load() checking the return value.

ignoring return value of ‘system’, declared with attribute warn_unused_result

And it also refactors the duplicate code of both
test_perf_event_all_cpu() and test_perf_event_task()

Cc: Teng Qin <qinteng@fb.com>
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
---
samples/bpf/trace_event_user.c | 27 ++++++++++++++++++++++++---
1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/samples/bpf/trace_event_user.c b/samples/bpf/trace_event_user.c
index 1fa1bec..d08046ab8 100644
--- a/samples/bpf/trace_event_user.c
+++ b/samples/bpf/trace_event_user.c
@@ -122,6 +122,16 @@ static void print_stacks(void)
}
}

+static inline int generate_load(void)
+{
+ if (system("dd if=/dev/zero of=/dev/null count=5000k status=none") < 0) {
+ printf("failed to generate some load with dd: %s\n", strerror(errno));
+ return -1;
+ }
+
+ return 0;
+}
+
static void test_perf_event_all_cpu(struct perf_event_attr *attr)
{
int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
@@ -142,7 +152,11 @@ static void test_perf_event_all_cpu(struct perf_event_attr *attr)
assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);
assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE) == 0);
}
- system("dd if=/dev/zero of=/dev/null count=5000k status=none");
+
+ if (generate_load() < 0) {
+ error = 1;
+ goto all_cpu_err;
+ }
print_stacks();
all_cpu_err:
for (i--; i >= 0; i--) {
@@ -156,7 +170,7 @@ static void test_perf_event_all_cpu(struct perf_event_attr *attr)

static void test_perf_event_task(struct perf_event_attr *attr)
{
- int pmu_fd;
+ int pmu_fd, error = 0;

/* per task perf event, enable inherit so the "dd ..." command can be traced properly.
* Enabling inherit will cause bpf_perf_prog_read_time helper failure.
@@ -171,10 +185,17 @@ static void test_perf_event_task(struct perf_event_attr *attr)
}
assert(ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);
assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE) == 0);
- system("dd if=/dev/zero of=/dev/null count=5000k status=none");
+
+ if (generate_load() < 0) {
+ error = 1;
+ goto err;
+ }
print_stacks();
+err:
ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
close(pmu_fd);
+ if (error)
+ int_exit(0);
}

static void test_bpf_perf_event(void)
--
2.7.4
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