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}