From: Brendan Jackman <jackmanb@google.com>
Date: Fri, 21 Feb 2025 18:25:46 +0000 (+0000)
Subject: selftests/mm: don't fail uffd-stress if too many CPUs
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=554273f6e5dac6cd47bd88363c8a2bd22c6de131;p=users%2Fjedix%2Flinux-maple.git

selftests/mm: don't fail uffd-stress if too many CPUs

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.

Link: https://lkml.kernel.org/r/20250221-mm-selftests-v2-7-28c4d66383c5@google.com
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Suggested-by: Mateusz Guzik <mjguzik@gmail.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index b28d39dbb2b2..fcd1bac69b13 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -435,6 +435,7 @@ static void sigalrm(int sig)
 
 int main(int argc, char **argv)
 {
+	unsigned long nr_cpus;
 	size_t bytes;
 
 	if (argc < 4)
@@ -453,7 +454,15 @@ 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) {