forked from Minki/linux
8cb75e0c4e
With various drivers wanting to inject idle time; we get people calling idle routines outside of the idle loop proper. Therefore we need to be extra careful about not missing TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations. While looking at this, I also realized there's a small window in the existing idle loop where we can miss TIF_NEED_RESCHED; when it hits right after the tif_need_resched() test at the end of the loop but right before the need_resched() test at the start of the loop. So move preempt_fold_need_resched() out of the loop where we're guaranteed to have TIF_NEED_RESCHED set. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
#ifndef _ASM_X86_MWAIT_H
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#define _ASM_X86_MWAIT_H
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#include <linux/sched.h>
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#define MWAIT_SUBSTATE_MASK 0xf
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#define MWAIT_CSTATE_MASK 0xf
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#define MWAIT_SUBSTATE_SIZE 4
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#define MWAIT_HINT2CSTATE(hint) (((hint) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK)
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#define MWAIT_HINT2SUBSTATE(hint) ((hint) & MWAIT_CSTATE_MASK)
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#define CPUID_MWAIT_LEAF 5
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#define CPUID5_ECX_EXTENSIONS_SUPPORTED 0x1
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#define CPUID5_ECX_INTERRUPT_BREAK 0x2
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#define MWAIT_ECX_INTERRUPT_BREAK 0x1
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static inline void __monitor(const void *eax, unsigned long ecx,
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unsigned long edx)
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{
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/* "monitor %eax, %ecx, %edx;" */
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asm volatile(".byte 0x0f, 0x01, 0xc8;"
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:: "a" (eax), "c" (ecx), "d"(edx));
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}
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static inline void __mwait(unsigned long eax, unsigned long ecx)
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{
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/* "mwait %eax, %ecx;" */
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asm volatile(".byte 0x0f, 0x01, 0xc9;"
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:: "a" (eax), "c" (ecx));
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}
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/*
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* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
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* which can obviate IPI to trigger checking of need_resched.
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* We execute MONITOR against need_resched and enter optimized wait state
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* through MWAIT. Whenever someone changes need_resched, we would be woken
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* up from MWAIT (without an IPI).
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*
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* New with Core Duo processors, MWAIT can take some hints based on CPU
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* capability.
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*/
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static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
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{
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if (!current_set_polling_and_test()) {
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if (static_cpu_has(X86_FEATURE_CLFLUSH_MONITOR)) {
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mb();
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clflush((void *)¤t_thread_info()->flags);
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mb();
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}
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__monitor((void *)¤t_thread_info()->flags, 0, 0);
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if (!need_resched())
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__mwait(eax, ecx);
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}
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current_clr_polling();
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}
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#endif /* _ASM_X86_MWAIT_H */
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