6dbde35308
It is an optimization and a cleanup, and adds the following new
generic percpu methods:
percpu_read()
percpu_write()
percpu_add()
percpu_sub()
percpu_and()
percpu_or()
percpu_xor()
and implements support for them on x86. (other architectures will fall
back to a default implementation)
The advantage is that for example to read a local percpu variable,
instead of this sequence:
return __get_cpu_var(var);
ffffffff8102ca2b: 48 8b 14 fd 80 09 74 mov -0x7e8bf680(,%rdi,8),%rdx
ffffffff8102ca32: 81
ffffffff8102ca33: 48 c7 c0 d8 59 00 00 mov $0x59d8,%rax
ffffffff8102ca3a: 48 8b 04 10 mov (%rax,%rdx,1),%rax
We can get a single instruction by using the optimized variants:
return percpu_read(var);
ffffffff8102ca3f: 65 48 8b 05 91 8f fd mov %gs:0x7efd8f91(%rip),%rax
I also cleaned up the x86-specific APIs and made the x86 code use
these new generic percpu primitives.
tj: * fixed generic percpu_sub() definition as Roel Kluin pointed out
* added percpu_and() for completeness's sake
* made generic percpu ops atomic against preemption
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Tejun Heo <tj@kernel.org>
55 lines
1.3 KiB
C
55 lines
1.3 KiB
C
#ifndef _ASM_X86_MMU_CONTEXT_32_H
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#define _ASM_X86_MMU_CONTEXT_32_H
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static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
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{
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#ifdef CONFIG_SMP
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if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
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percpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
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#endif
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}
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static inline void switch_mm(struct mm_struct *prev,
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struct mm_struct *next,
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struct task_struct *tsk)
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{
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int cpu = smp_processor_id();
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if (likely(prev != next)) {
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/* stop flush ipis for the previous mm */
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cpu_clear(cpu, prev->cpu_vm_mask);
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#ifdef CONFIG_SMP
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percpu_write(cpu_tlbstate.state, TLBSTATE_OK);
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percpu_write(cpu_tlbstate.active_mm, next);
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#endif
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cpu_set(cpu, next->cpu_vm_mask);
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/* Re-load page tables */
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load_cr3(next->pgd);
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/*
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* load the LDT, if the LDT is different:
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*/
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if (unlikely(prev->context.ldt != next->context.ldt))
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load_LDT_nolock(&next->context);
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}
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#ifdef CONFIG_SMP
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else {
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percpu_write(cpu_tlbstate.state, TLBSTATE_OK);
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BUG_ON(percpu_read(cpu_tlbstate.active_mm) != next);
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if (!cpu_test_and_set(cpu, next->cpu_vm_mask)) {
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/* We were in lazy tlb mode and leave_mm disabled
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* tlb flush IPI delivery. We must reload %cr3.
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*/
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load_cr3(next->pgd);
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load_LDT_nolock(&next->context);
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}
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}
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#endif
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}
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#define deactivate_mm(tsk, mm) \
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asm("movl %0,%%gs": :"r" (0));
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#endif /* _ASM_X86_MMU_CONTEXT_32_H */
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