4307d1e5ad
dont use the vgetcpu tcache - it's causing problems with tasks migrating, they'll see the old cache up to a jiffy after the migration, further increasing the costs of the migration. In the worst case they see a complete bogus information from the tcache, when a sys_getcpu() call "invalidated" the cache info by incrementing the jiffies _and_ the cpuid info in the cache and the following vdso_getcpu() call happens after vdso_jiffies have been incremented. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
36 lines
827 B
C
36 lines
827 B
C
/*
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* Copyright 2006 Andi Kleen, SUSE Labs.
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* Subject to the GNU Public License, v.2
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*
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* Fast user context implementation of getcpu()
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*/
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#include <linux/kernel.h>
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#include <linux/getcpu.h>
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#include <linux/jiffies.h>
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#include <linux/time.h>
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#include <asm/vsyscall.h>
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#include <asm/vgtod.h>
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#include "vextern.h"
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long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
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{
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unsigned int dummy, p;
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if (*vdso_vgetcpu_mode == VGETCPU_RDTSCP) {
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/* Load per CPU data from RDTSCP */
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rdtscp(dummy, dummy, p);
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} else {
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/* Load per CPU data from GDT */
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asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
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}
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if (cpu)
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*cpu = p & 0xfff;
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if (node)
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*node = p >> 12;
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return 0;
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}
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long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
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__attribute__((weak, alias("__vdso_getcpu")));
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