[LTP] [PATCH 6/6] fzsync: Check processor affinity

[Richard Palethorpe]

It is useful for testing Fuzzy Sync itself to set the CPU affinity to
a single core. The current processes affinity does not effect
tst_ncpus(), but we can get the affinity separately.

Note that checking this still does not guarantee we will use yield
when restricted to only one core. We would have to periodically probe
which CPUs threads are running on until we detect more than one CPU.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
 include/tst_fuzzy_sync.h | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/tst_fuzzy_sync.h b/include/tst_fuzzy_sync.h
index 36a604e13..ea356ab44 100644
--- a/include/tst_fuzzy_sync.h
+++ b/include/tst_fuzzy_sync.h
@@ -59,9 +59,11 @@
  * @sa tst_fzsync_pair
  */
 
+#define _GNU_SOURCE
+
 #include <math.h>
 #include <pthread.h>
-#include <sched.h>
+#include "lapi/cpuset.h"
 #include <stdbool.h>
 #include <stdlib.h>
 #include <sys/time.h>
@@ -213,12 +215,26 @@ struct tst_fzsync_pair {
  */
 static void tst_fzsync_pair_init(struct tst_fzsync_pair *pair)
 {
+	long ncpus = tst_ncpus();
+#ifdef CPU_COUNT
+	size_t cpusz = CPU_ALLOC_SIZE(ncpus);
+	cpu_set_t *cpus = CPU_ALLOC(ncpus);
+
+	if (sched_getaffinity(0, cpusz, cpus)) {
+		tst_res(TWARN | TERRNO, "sched_getaffinity(0, %zu, %zx)",
+			cpusz, (size_t)cpus);
+	} else {
+		ncpus = CPU_COUNT(cpus);
+	}
+	free(cpus);
+#endif
+
 	CHK(avg_alpha, 0, 1, 0.25);
 	CHK(min_samples, 20, INT_MAX, 1024);
 	CHK(max_dev_ratio, 0, 1, 0.1);
 	CHK(exec_time_p, 0, 1, 0.5);
 	CHK(exec_loops, 20, INT_MAX, 3000000);
-	CHK(yield_in_wait, 0, 1, (tst_ncpus() <= 1));
+	CHK(yield_in_wait, 0, 1, (ncpus <= 1));
 }
 #undef CHK
 
-- 
2.30.1