[PATCH v3 19/21] selftests/resctrl: Fix checking for < 0 for unsigned values

Fenghua Yu
2020-10-20T23:52:15Z

Dan reported following static checker warnings

tools/testing/selftests/resctrl/resctrl_val.c:545 measure_vals()
warn: 'bw_imc' unsigned <= 0

tools/testing/selftests/resctrl/resctrl_val.c:549 measure_vals()
warn: 'bw_resc_end' unsigned <= 0

These warnings are reported because
1. measure_vals() declares 'bw_imc' and 'bw_resc_end' as unsigned long
variables
2. Return value of get_mem_bw_imc() and get_mem_bw_resctrl() are assigned
to 'bw_imc' and 'bw_resc_end' respectively
3. The returned values are checked for <= 0 to see if the calls failed

Checking for < 0 for an unsigned value doesn't make any sense.

Fix this issue by changing the implementation of get_mem_bw_imc() and
get_mem_bw_resctrl() such that they now accept reference to a variable
and set the variable appropriately upon success and return 0, else return
< 0 on error.

Fixes: 7f4d257e3a2a ("selftests/resctrl: Add callback to start a benchmark")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
tools/testing/selftests/resctrl/resctrl_val.c | 41 +++++++++++--------
1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index 88f9b641d753..f723d8534cf2 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -300,9 +300,9 @@ static int initialize_mem_bw_imc(void)
* Memory B/W utilized by a process on a socket can be calculated using
* iMC counters. Perf events are used to read these counters.
*
- * Return: >= 0 on success. < 0 on failure.
+ * Return: = 0 on success. < 0 on failure.
*/
-static float get_mem_bw_imc(int cpu_no, char *bw_report)
+static int get_mem_bw_imc(int cpu_no, char *bw_report, float *bw_imc)
{
float reads, writes, of_mul_read, of_mul_write;
int imc, j, ret;
@@ -373,13 +373,18 @@ static float get_mem_bw_imc(int cpu_no, char *bw_report)
close(imc_counters_config[imc][WRITE].fd);
}

- if (strcmp(bw_report, "reads") == 0)
- return reads;
+ if (strcmp(bw_report, "reads") == 0) {
+ *bw_imc = reads;
+ return 0;
+ }

- if (strcmp(bw_report, "writes") == 0)
- return writes;
+ if (strcmp(bw_report, "writes") == 0) {
+ *bw_imc = writes;
+ return 0;
+ }

- return (reads + writes);
+ *bw_imc = reads + writes;
+ return 0;
}

void set_mbm_path(const char *ctrlgrp, const char *mongrp, int resource_id)
@@ -438,9 +443,8 @@ static void initialize_mem_bw_resctrl(const char *ctrlgrp, const char *mongrp,
* 1. If con_mon grp is given, then read from it
* 2. If con_mon grp is not given, then read from root con_mon grp
*/
-static unsigned long get_mem_bw_resctrl(void)
+static int get_mem_bw_resctrl(unsigned long *mbm_total)
{
- unsigned long mbm_total = 0;
FILE *fp;

fp = fopen(mbm_total_path, "r");
@@ -449,7 +453,7 @@ static unsigned long get_mem_bw_resctrl(void)

return -1;
}
- if (fscanf(fp, "%lu", &mbm_total) <= 0) {
+ if (fscanf(fp, "%lu", mbm_total) <= 0) {
perror("Could not get mbm local bytes");
fclose(fp);

@@ -457,7 +461,7 @@ static unsigned long get_mem_bw_resctrl(void)
}
fclose(fp);

- return mbm_total;
+ return 0;
}

pid_t bm_pid, ppid;
@@ -549,7 +553,8 @@ static void initialize_llc_occu_resctrl(const char *ctrlgrp, const char *mongrp,
static int
measure_vals(struct resctrl_val_param *param, unsigned long *bw_resc_start)
{
- unsigned long bw_imc, bw_resc, bw_resc_end;
+ unsigned long bw_resc, bw_resc_end;
+ float bw_imc;
int ret;

/*
@@ -559,13 +564,13 @@ measure_vals(struct resctrl_val_param *param, unsigned long *bw_resc_start)
* Compare the two values to validate resctrl value.
* It takes 1sec to measure the data.
*/
- bw_imc = get_mem_bw_imc(param->cpu_no, param->bw_report);
- if (bw_imc <= 0)
- return bw_imc;
+ ret = get_mem_bw_imc(param->cpu_no, param->bw_report, &bw_imc);
+ if (ret < 0)
+ return ret;

- bw_resc_end = get_mem_bw_resctrl();
- if (bw_resc_end <= 0)
- return bw_resc_end;
+ ret = get_mem_bw_resctrl(&bw_resc_end);
+ if (ret < 0)
+ return ret;

bw_resc = (bw_resc_end - *bw_resc_start) / MB;
ret = print_results_bw(param->filename, bm_pid, bw_imc, bw_resc);
--
2.29.0