You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
50 lines
1.4 KiB
50 lines
1.4 KiB
/*
|
|
* Copyright 2006 Andi Kleen, SUSE Labs.
|
|
* Subject to the GNU Public License, v.2
|
|
*
|
|
* Fast user context implementation of getcpu()
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/getcpu.h>
|
|
#include <linux/jiffies.h>
|
|
#include <linux/time.h>
|
|
#include <asm/vsyscall.h>
|
|
#include <asm/vgtod.h>
|
|
#include "vextern.h"
|
|
|
|
long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
|
|
{
|
|
unsigned int dummy, p;
|
|
unsigned long j = 0;
|
|
|
|
/* Fast cache - only recompute value once per jiffies and avoid
|
|
relatively costly rdtscp/cpuid otherwise.
|
|
This works because the scheduler usually keeps the process
|
|
on the same CPU and this syscall doesn't guarantee its
|
|
results anyways.
|
|
We do this here because otherwise user space would do it on
|
|
its own in a likely inferior way (no access to jiffies).
|
|
If you don't like it pass NULL. */
|
|
if (tcache && tcache->blob[0] == (j = *vdso_jiffies)) {
|
|
p = tcache->blob[1];
|
|
} else if (*vdso_vgetcpu_mode == VGETCPU_RDTSCP) {
|
|
/* Load per CPU data from RDTSCP */
|
|
rdtscp(dummy, dummy, p);
|
|
} else {
|
|
/* Load per CPU data from GDT */
|
|
asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
|
|
}
|
|
if (tcache) {
|
|
tcache->blob[0] = j;
|
|
tcache->blob[1] = p;
|
|
}
|
|
if (cpu)
|
|
*cpu = p & 0xfff;
|
|
if (node)
|
|
*node = p >> 12;
|
|
return 0;
|
|
}
|
|
|
|
long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
|
|
__attribute__((weak, alias("__vdso_getcpu")));
|
|
|