[PATCH 4.19 112/168] selftests/powerpc: Fix online CPU selection

Greg Kroah-Hartman
2020-08-17T17:43:48Z

From: Sandipan Das <sandipan@linux.ibm.com>

[ Upstream commit dfa03fff86027e58c8dba5c03ae68150d4e513ad ]

The size of the CPU affinity mask must be large enough for
systems with a very large number of CPUs. Otherwise, tests
which try to determine the first online CPU by calling
sched_getaffinity() will fail. This makes sure that the size
of the allocated affinity mask is dependent on the number of
CPUs as reported by get_nprocs_conf().

Fixes: 3752e453f6ba ("selftests/powerpc: Add tests of PMU EBBs")
Reported-by: Shirisha Ganta <shiganta@in.ibm.com>
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a408c4b8e9a23bb39b539417a21eb0ff47bb5127.1596084858.git.sandipan@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/powerpc/utils.c | 37 +++++++++++++++++--------
1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/powerpc/utils.c b/tools/testing/selftests/powerpc/utils.c
index aa8fc1e6365bf..ba0959d454b3c 100644
--- a/tools/testing/selftests/powerpc/utils.c
+++ b/tools/testing/selftests/powerpc/utils.c
@@ -13,6 +13,7 @@
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
+#include <sys/sysinfo.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <unistd.h>
@@ -83,28 +84,40 @@ void *get_auxv_entry(int type)

int pick_online_cpu(void)
{
- cpu_set_t mask;
- int cpu;
+ int ncpus, cpu = -1;
+ cpu_set_t *mask;
+ size_t size;
+
+ ncpus = get_nprocs_conf();
+ size = CPU_ALLOC_SIZE(ncpus);
+ mask = CPU_ALLOC(ncpus);
+ if (!mask) {
+ perror("malloc");
+ return -1;
+ }

- CPU_ZERO(&mask);
+ CPU_ZERO_S(size, mask);

- if (sched_getaffinity(0, sizeof(mask), &mask)) {
+ if (sched_getaffinity(0, size, mask)) {
perror("sched_getaffinity");
- return -1;
+ goto done;
}

/* We prefer a primary thread, but skip 0 */
- for (cpu = 8; cpu < CPU_SETSIZE; cpu += 8)
- if (CPU_ISSET(cpu, &mask))
- return cpu;
+ for (cpu = 8; cpu < ncpus; cpu += 8)
+ if (CPU_ISSET_S(cpu, size, mask))
+ goto done;

/* Search for anything, but in reverse */
- for (cpu = CPU_SETSIZE - 1; cpu >= 0; cpu--)
- if (CPU_ISSET(cpu, &mask))
- return cpu;
+ for (cpu = ncpus - 1; cpu >= 0; cpu--)
+ if (CPU_ISSET_S(cpu, size, mask))
+ goto done;

printf("No cpus in affinity mask?!\n");
- return -1;
+
+done:
+ CPU_FREE(mask);
+ return cpu;
}

bool is_ppc64le(void)
--
2.25.1