* [PATCH v3] selftests: powerpc: Fix online CPU selection
@ 2020-07-30 5:08 Sandipan Das
2020-08-02 13:35 ` Michael Ellerman
0 siblings, 1 reply; 2+ messages in thread
From: Sandipan Das @ 2020-07-30 5:08 UTC (permalink / raw)
To: mpe; +Cc: srikar, kamalesh, shiganta, nasastry, harish, linuxppc-dev
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>
---
Previous versions can be found at:
v2: https://lore.kernel.org/linuxppc-dev/20200609073733.997643-1-sandipan@linux.ibm.com/
v1: https://lore.kernel.org/linuxppc-dev/20200608144212.985144-1-sandipan@linux.ibm.com/
Changes in v3:
- Use get_nprocs_conf() instead of get_nprocs() as suggested by
Srikar to cope with test failures that Michael reported for
sparse SMT setups.
Changes in v2:
- Added NULL check for the affinity mask as suggested by Kamalesh.
- Changed "cpu set" to "CPU affinity mask" in the commit message.
---
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 933678f1ed0a0..18b6a773d5c73 100644
--- a/tools/testing/selftests/powerpc/utils.c
+++ b/tools/testing/selftests/powerpc/utils.c
@@ -16,6 +16,7 @@
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
+#include <sys/sysinfo.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <unistd.h>
@@ -88,28 +89,40 @@ 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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] selftests: powerpc: Fix online CPU selection
2020-07-30 5:08 [PATCH v3] selftests: powerpc: Fix online CPU selection Sandipan Das
@ 2020-08-02 13:35 ` Michael Ellerman
0 siblings, 0 replies; 2+ messages in thread
From: Michael Ellerman @ 2020-08-02 13:35 UTC (permalink / raw)
To: Sandipan Das, mpe
Cc: srikar, kamalesh, shiganta, nasastry, harish, linuxppc-dev
On Thu, 30 Jul 2020 10:38:46 +0530, Sandipan Das wrote:
> 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().
Applied to powerpc/next.
[1/1] selftests/powerpc: Fix online CPU selection
https://git.kernel.org/powerpc/c/dfa03fff86027e58c8dba5c03ae68150d4e513ad
cheers
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