1#define _GNU_SOURCE
2#include <errno.h>
3#include <sched.h>
4#include "syscall.h"
5#include "atomic.h"
6
7#ifdef VDSO_GETCPU_SYM
8
9static void *volatile vdso_func;
10
11typedef long (*getcpu_f)(unsigned *, unsigned *, void *);
12
13static long getcpu_init(unsigned *cpu, unsigned *node, void *unused)
14{
15 void *p = __vdsosym(VDSO_GETCPU_VER, VDSO_GETCPU_SYM);
16 getcpu_f f = (getcpu_f)p;
17 a_cas_p(&vdso_func, (void *)getcpu_init, p);
18 return f ? f(cpu, node, unused) : -ENOSYS;
19}
20
21static void *volatile vdso_func = (void *)getcpu_init;
22
23#endif
24
25int sched_getcpu(void)
26{
27 int r;
28 unsigned cpu;
29
30#ifdef VDSO_GETCPU_SYM
31 getcpu_f f = (getcpu_f)vdso_func;
32 if (f) {
33 r = f(&cpu, 0, 0);
34 if (!r) return cpu;
35 if (r != -ENOSYS) return __syscall_ret(r);
36 }
37#endif
38
39 r = __syscall(SYS_getcpu, &cpu, 0, 0);
40 if (!r) return cpu;
41 return __syscall_ret(r);
42}
43