* [PATCH v2] selftests: powerpc: Fix online CPU selection
@ 2020-06-09 7:37 Sandipan Das
2020-07-29 13:47 ` Michael Ellerman
2020-07-29 16:03 ` Srikar Dronamraju
0 siblings, 2 replies; 4+ messages in thread
From: Sandipan Das @ 2020-06-09 7:37 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().
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:
v1: https://lore.kernel.org/linuxppc-dev/20200608144212.985144-1-sandipan@linux.ibm.com/
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 933678f1ed0a..798fa8fdd5f4 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();
+ 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] 4+ messages in thread
* Re: [PATCH v2] selftests: powerpc: Fix online CPU selection
2020-06-09 7:37 [PATCH v2] selftests: powerpc: Fix online CPU selection Sandipan Das
@ 2020-07-29 13:47 ` Michael Ellerman
2020-07-29 16:03 ` Srikar Dronamraju
1 sibling, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2020-07-29 13:47 UTC (permalink / raw)
To: Sandipan Das; +Cc: srikar, kamalesh, shiganta, nasastry, harish, linuxppc-dev
Sandipan Das <sandipan@linux.ibm.com> writes:
> 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().
>
> 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:
> v1: https://lore.kernel.org/linuxppc-dev/20200608144212.985144-1-sandipan@linux.ibm.com/
>
> 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.
This sometimes breaks, eg:
# ./count_instructions
test: count_instructions
tags: git_version:v5.8-rc2-327-g9a1d992a7eb7
sched_getaffinity: Invalid argument
[FAIL] Test FAILED on line 123
failure: count_instructions
This system has a messed up SMT setup, but the old code was able to cope
with it:
# ppc64_cpu --info
Core 0: 0* 1* 2 3 4 5 6 7
Core 1: 8 9 10* 11* 12 13 14 15
Core 2: 16 17 18 19 20 21 22 23
Core 3: 24 25 26 27 28 29 30 31
Core 4: 32 33 34 35 36 37 38 39
Core 5: 40 41 42 43 44 45 46 47
Core 6: 48 49 50 51 52 53 54 55
Core 7: 56 57 58 59 60 61 62 63
Core 8: 64 65 66 67 68 69 70 71
Core 9: 72 73 74 75 76 77 78 79
Core 10: 80 81 82 83 84 85 86 87
Core 11: 88 89 90 91 92 93 94 95
Core 12: 96 97 98 99 100* 101* 102* 103*
Core 13: 104* 105* 106* 107* 108* 109* 110* 111*
Core 14: 112* 113* 114* 115* 116* 117* 118* 119*
Core 15: 120 121 122 123 124 125 126 127
Core 16: 128 129 130 131 132 133 134 135
Core 17: 136 137 138 139 140 141 142 143
Core 18: 144 145 146 147 148 149 150 151
Core 19: 152 153 154 155 156 157 158 159
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] selftests: powerpc: Fix online CPU selection
2020-06-09 7:37 [PATCH v2] selftests: powerpc: Fix online CPU selection Sandipan Das
2020-07-29 13:47 ` Michael Ellerman
@ 2020-07-29 16:03 ` Srikar Dronamraju
2020-07-30 4:59 ` Sandipan Das
1 sibling, 1 reply; 4+ messages in thread
From: Srikar Dronamraju @ 2020-07-29 16:03 UTC (permalink / raw)
To: Sandipan Das; +Cc: kamalesh, shiganta, nasastry, harish, linuxppc-dev
* Sandipan Das <sandipan@linux.ibm.com> [2020-06-09 13:07:33]:
> 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().
>
> 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:
> v1: https://lore.kernel.org/linuxppc-dev/20200608144212.985144-1-sandipan@linux.ibm.com/
>
> @@ -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();
Please use get_nprocs_conf or sysconf(_SC_NPROCESSORS_CONF). The manpage
seems to suggest the latter. Not sure how accurate the manpage is.
get_nprocs is returning online cpus and when smt is off, the cpu numbers
would be sparse and hence the result from get_nprocs wouldn't be ideal for
allocating cpumask. However get_nprocs_conf would return the max configured
cpus and would be able to handle it.
I think this was the same situation hit by Michael Ellerman.
> + size = CPU_ALLOC_SIZE(ncpus);
> + mask = CPU_ALLOC(ncpus);
> + if (!mask) {
> + perror("malloc");
> + return -1;
> + }
>
--
Thanks and Regards
Srikar Dronamraju
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] selftests: powerpc: Fix online CPU selection
2020-07-29 16:03 ` Srikar Dronamraju
@ 2020-07-30 4:59 ` Sandipan Das
0 siblings, 0 replies; 4+ messages in thread
From: Sandipan Das @ 2020-07-30 4:59 UTC (permalink / raw)
To: Srikar Dronamraju, mpe; +Cc: shiganta, nasastry, harish, linuxppc-dev, kamalesh
Hi Srikar, Michael,
On 29/07/20 9:33 pm, Srikar Dronamraju wrote:
> * Sandipan Das <sandipan@linux.ibm.com> [2020-06-09 13:07:33]:
>
>> 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().
>>
>> 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:
>> v1: https://lore.kernel.org/linuxppc-dev/20200608144212.985144-1-sandipan@linux.ibm.com/
>>
>> @@ -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();
>
> Please use get_nprocs_conf or sysconf(_SC_NPROCESSORS_CONF). The manpage
> seems to suggest the latter. Not sure how accurate the manpage is.
>
> get_nprocs is returning online cpus and when smt is off, the cpu numbers
> would be sparse and hence the result from get_nprocs wouldn't be ideal for
> allocating cpumask. However get_nprocs_conf would return the max configured
> cpus and would be able to handle it.
>
> I think this was the same situation hit by Michael Ellerman.
>
Yes, that seems to be the case. Thanks for testing this.
Will fix this in v3.
- Sandipan
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-06-09 7:37 [PATCH v2] selftests: powerpc: Fix online CPU selection Sandipan Das
2020-07-29 13:47 ` Michael Ellerman
2020-07-29 16:03 ` Srikar Dronamraju
2020-07-30 4:59 ` Sandipan Das
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