diff options
Diffstat (limited to 'arch/x86/vdso/vgetcpu.c')
-rw-r--r-- | arch/x86/vdso/vgetcpu.c | 19 |
1 files changed, 2 insertions, 17 deletions
diff --git a/arch/x86/vdso/vgetcpu.c b/arch/x86/vdso/vgetcpu.c index 91f6e85d0fc2..3b1ae1abfba9 100644 --- a/arch/x86/vdso/vgetcpu.c +++ b/arch/x86/vdso/vgetcpu.c | |||
@@ -13,32 +13,17 @@ | |||
13 | #include <asm/vgtod.h> | 13 | #include <asm/vgtod.h> |
14 | #include "vextern.h" | 14 | #include "vextern.h" |
15 | 15 | ||
16 | long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache) | 16 | long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused) |
17 | { | 17 | { |
18 | unsigned int dummy, p; | 18 | unsigned int dummy, p; |
19 | unsigned long j = 0; | ||
20 | 19 | ||
21 | /* Fast cache - only recompute value once per jiffies and avoid | 20 | if (*vdso_vgetcpu_mode == VGETCPU_RDTSCP) { |
22 | relatively costly rdtscp/cpuid otherwise. | ||
23 | This works because the scheduler usually keeps the process | ||
24 | on the same CPU and this syscall doesn't guarantee its | ||
25 | results anyways. | ||
26 | We do this here because otherwise user space would do it on | ||
27 | its own in a likely inferior way (no access to jiffies). | ||
28 | If you don't like it pass NULL. */ | ||
29 | if (tcache && tcache->blob[0] == (j = *vdso_jiffies)) { | ||
30 | p = tcache->blob[1]; | ||
31 | } else if (*vdso_vgetcpu_mode == VGETCPU_RDTSCP) { | ||
32 | /* Load per CPU data from RDTSCP */ | 21 | /* Load per CPU data from RDTSCP */ |
33 | rdtscp(dummy, dummy, p); | 22 | rdtscp(dummy, dummy, p); |
34 | } else { | 23 | } else { |
35 | /* Load per CPU data from GDT */ | 24 | /* Load per CPU data from GDT */ |
36 | asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG)); | 25 | asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG)); |
37 | } | 26 | } |
38 | if (tcache) { | ||
39 | tcache->blob[0] = j; | ||
40 | tcache->blob[1] = p; | ||
41 | } | ||
42 | if (cpu) | 27 | if (cpu) |
43 | *cpu = p & 0xfff; | 28 | *cpu = p & 0xfff; |
44 | if (node) | 29 | if (node) |