forked from Minki/linux
72cd652b73
The affinity code in "affinity_set" function access array named
"sched_cpus". The size for this array is allocated in affinity_setup
function which is nothing but value from get_cpu_set_size. This is used
to contain the cpumask value for each cpu.
While setting bit for each cpu, it calls "set_bit" function which access
index in sched_cpus array. If we provide a command-line option to -C
which is more than the number of CPU's present in the system, the
set_bit could access an array member which is out-of the array size.
This is because currently, there is no boundary check for the CPU. This
will result in seg fault:
<<>>
./perf stat -C 12323431 ls
Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS
Segmentation fault (core dumped)
<<>>
Fix this by adding boundary check for the array.
After the fix from powerpc system:
<<>>
./perf stat -C 12323431 ls 1>out
Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS
Performance counter stats for 'CPU(s) 12323431':
<not supported> msec cpu-clock
<not supported> context-switches
<not supported> cpu-migrations
<not supported> page-faults
<not supported> cycles
<not supported> instructions
<not supported> branches
<not supported> branch-misses
0.001192373 seconds time elapsed
<<>>
Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20220905141929.7171-1-atrajeev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
86 lines
2.0 KiB
C
86 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/* Manage affinity to optimize IPIs inside the kernel perf API. */
|
|
#define _GNU_SOURCE 1
|
|
#include <sched.h>
|
|
#include <stdlib.h>
|
|
#include <linux/bitmap.h>
|
|
#include <linux/zalloc.h>
|
|
#include "perf.h"
|
|
#include "cpumap.h"
|
|
#include "affinity.h"
|
|
|
|
static int get_cpu_set_size(void)
|
|
{
|
|
int sz = cpu__max_cpu().cpu + 8 - 1;
|
|
/*
|
|
* sched_getaffinity doesn't like masks smaller than the kernel.
|
|
* Hopefully that's big enough.
|
|
*/
|
|
if (sz < 4096)
|
|
sz = 4096;
|
|
return sz / 8;
|
|
}
|
|
|
|
int affinity__setup(struct affinity *a)
|
|
{
|
|
int cpu_set_size = get_cpu_set_size();
|
|
|
|
a->orig_cpus = bitmap_zalloc(cpu_set_size * 8);
|
|
if (!a->orig_cpus)
|
|
return -1;
|
|
sched_getaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
|
|
a->sched_cpus = bitmap_zalloc(cpu_set_size * 8);
|
|
if (!a->sched_cpus) {
|
|
zfree(&a->orig_cpus);
|
|
return -1;
|
|
}
|
|
bitmap_zero((unsigned long *)a->sched_cpus, cpu_set_size);
|
|
a->changed = false;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* perf_event_open does an IPI internally to the target CPU.
|
|
* It is more efficient to change perf's affinity to the target
|
|
* CPU and then set up all events on that CPU, so we amortize
|
|
* CPU communication.
|
|
*/
|
|
void affinity__set(struct affinity *a, int cpu)
|
|
{
|
|
int cpu_set_size = get_cpu_set_size();
|
|
|
|
/*
|
|
* Return:
|
|
* - if cpu is -1
|
|
* - restrict out of bound access to sched_cpus
|
|
*/
|
|
if (cpu == -1 || ((cpu >= (cpu_set_size * 8))))
|
|
return;
|
|
|
|
a->changed = true;
|
|
set_bit(cpu, a->sched_cpus);
|
|
/*
|
|
* We ignore errors because affinity is just an optimization.
|
|
* This could happen for example with isolated CPUs or cpusets.
|
|
* In this case the IPIs inside the kernel's perf API still work.
|
|
*/
|
|
sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->sched_cpus);
|
|
clear_bit(cpu, a->sched_cpus);
|
|
}
|
|
|
|
static void __affinity__cleanup(struct affinity *a)
|
|
{
|
|
int cpu_set_size = get_cpu_set_size();
|
|
|
|
if (a->changed)
|
|
sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
|
|
zfree(&a->sched_cpus);
|
|
zfree(&a->orig_cpus);
|
|
}
|
|
|
|
void affinity__cleanup(struct affinity *a)
|
|
{
|
|
if (a != NULL)
|
|
__affinity__cleanup(a);
|
|
}
|