101 lines
1.6 KiB
C
101 lines
1.6 KiB
C
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/*
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* Copyright 2013-2015, Michael Ellerman, IBM Corp.
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* Licensed under GPLv2.
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*/
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#define _GNU_SOURCE /* For CPU_ZERO etc. */
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#include <elf.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <link.h>
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#include <sched.h>
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#include <stdio.h>
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#include <sys/stat.h>
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#include <sys/sysinfo.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "utils.h"
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static char auxv[4096];
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void *get_auxv_entry(int type)
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{
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ElfW(auxv_t) *p;
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void *result;
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ssize_t num;
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int fd;
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fd = open("/proc/self/auxv", O_RDONLY);
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if (fd == -1) {
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perror("open");
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return NULL;
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}
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result = NULL;
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num = read(fd, auxv, sizeof(auxv));
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if (num < 0) {
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perror("read");
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goto out;
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}
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if (num > sizeof(auxv)) {
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printf("Overflowed auxv buffer\n");
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goto out;
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}
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p = (ElfW(auxv_t) *)auxv;
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while (p->a_type != AT_NULL) {
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if (p->a_type == type) {
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result = (void *)p->a_un.a_val;
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break;
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}
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p++;
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}
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out:
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close(fd);
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return result;
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}
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int pick_online_cpu(void)
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{
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int ncpus, cpu = -1;
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cpu_set_t *mask;
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size_t size;
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ncpus = get_nprocs_conf();
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size = CPU_ALLOC_SIZE(ncpus);
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mask = CPU_ALLOC(ncpus);
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if (!mask) {
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perror("malloc");
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return -1;
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}
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CPU_ZERO_S(size, mask);
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if (sched_getaffinity(0, size, mask)) {
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perror("sched_getaffinity");
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goto done;
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}
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/* We prefer a primary thread, but skip 0 */
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for (cpu = 8; cpu < ncpus; cpu += 8)
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if (CPU_ISSET_S(cpu, size, mask))
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goto done;
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/* Search for anything, but in reverse */
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for (cpu = ncpus - 1; cpu >= 0; cpu--)
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if (CPU_ISSET_S(cpu, size, mask))
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goto done;
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printf("No cpus in affinity mask?!\n");
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done:
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CPU_FREE(mask);
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return cpu;
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}
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