[PATCH v3 06/10] selftests/mm: Don't fail uffd-stress if too many CPUs

[Brendan Jackman <jackmanb@google.com>]

This calculation divides a fixed parameter by an environment-dependent
parameter i.e. the number of CPUs.

The simple way to avoid machine-specific failures here is to just put a
cap on the max value of the latter.

Suggested-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/uffd-stress.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index efe2051c393096e237d942c04a264b6611a6e127..5656128590373ed376b3b5d9259e5ca3867a4099 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -434,6 +434,7 @@ static void sigalrm(int sig)
 
 int main(int argc, char **argv)
 {
+	unsigned long nr_cpus;
 	size_t bytes;
 
 	if (argc < 4)
@@ -452,7 +453,15 @@ int main(int argc, char **argv)
 		return KSFT_SKIP;
 	}
 
-	nr_threads = sysconf(_SC_NPROCESSORS_ONLN);
+	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+	if (nr_cpus > 32) {
+		/* Don't let calculation below go to zero. */
+		ksft_print_msg("_SC_NPROCESSORS_ONLN (%lu) too large, capping nr_threads to 32\n",
+			       nr_cpus);
+		nr_threads = 32;
+	} else {
+		nr_cpus = nr_threads;
+	}
 
 	nr_pages_per_cpu = bytes / page_size / nr_threads;
 	if (!nr_pages_per_cpu) {

-- 
2.48.1.711.g2feabab25a-goog