[PATCH v3 18/21] selftests/resctrl: Fix incorrect parsing of iMC counters

Fenghua Yu
2020-10-20T23:51:43Z

iMC (Integrated Memory Controller) counters are usually at
"/sys/bus/event_source/devices/" and are named as "uncore_imc_<n>".
num_of_imcs() function tries to count number of such iMC counters so that
it could appropriately initialize required number of perf_attr structures
that could be used to read these iMC counters.

num_of_imcs() function assumes that all the directories under this path
that start with "uncore_imc" are iMC counters. But, on some systems there
could be directories named as "uncore_imc_free_running" which aren't iMC
counters. Trying to read from such directories will result in "not found
file" errors and MBM/MBA tests will fail.

Hence, fix the logic in num_of_imcs() such that it looks at the first
character after "uncore_imc_" to check if it's a numerical digit or not. If
it's a digit then the directory represents an iMC counter, else, skip the
directory.

Fixes: 7f4d257e3a2a ("selftests/resctrl: Add callback to start a benchmark")
Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
tools/testing/selftests/resctrl/resctrl_val.c | 22 +++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index 270cd95e0026..88f9b641d753 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -221,8 +221,8 @@ static int read_from_imc_dir(char *imc_dir, int count)
*/
static int num_of_imcs(void)
{
+ char imc_dir[512], *temp;
unsigned int count = 0;
- char imc_dir[512];
struct dirent *ep;
int ret;
DIR *dp;
@@ -230,7 +230,25 @@ static int num_of_imcs(void)
dp = opendir(DYN_PMU_PATH);
if (dp) {
while ((ep = readdir(dp))) {
- if (strstr(ep->d_name, UNCORE_IMC)) {
+ temp = strstr(ep->d_name, UNCORE_IMC);
+ if (!temp)
+ continue;
+
+ /*
+ * imc counters are named as "uncore_imc_<n>", hence
+ * increment the pointer to point to <n>. Note that
+ * sizeof(UNCORE_IMC) would count for null character as
+ * well and hence the last underscore character in
+ * uncore_imc'_' need not be counted.
+ */
+ temp = temp + sizeof(UNCORE_IMC);
+
+ /*
+ * Some directories under "DYN_PMU_PATH" could have
+ * names like "uncore_imc_free_running", hence, check if
+ * first character is a numerical digit or not.
+ */
+ if (temp[0] >= '0' && temp[0] <= '9') {
sprintf(imc_dir, "%s/%s/", DYN_PMU_PATH,
ep->d_name);
ret = read_from_imc_dir(imc_dir, count);
--
2.29.0