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79ab11cdb9
For spinning loops people do often use barrier() or cpu_relax(). For most architectures cpu_relax and barrier are the same, but on some architectures cpu_relax can add some latency. For example on power,sparc64 and arc, cpu_relax can shift the CPU towards other hardware threads in an SMT environment. On s390 cpu_relax does even more, it uses an hypercall to the hypervisor to give up the timeslice. In contrast to the SMT yielding this can result in larger latencies. In some places this latency is unwanted, so another variant "cpu_relax_lowlatency" was introduced. Before this is used in more and more places, lets revert the logic and provide a cpu_relax_yield that can be called in places where yielding is more important than latency. By default this is the same as cpu_relax on all architectures. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Noam Camus <noamc@ezchip.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: linuxppc-dev@lists.ozlabs.org Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1477386195-32736-2-git-send-email-borntraeger@de.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
178 lines
4.3 KiB
C
178 lines
4.3 KiB
C
/* MN10300 Processor specifics
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*
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* Copyright (C) 2007 Matsushita Electric Industrial Co., Ltd.
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#ifndef _ASM_PROCESSOR_H
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#define _ASM_PROCESSOR_H
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#include <linux/threads.h>
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#include <linux/thread_info.h>
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#include <asm/page.h>
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#include <asm/ptrace.h>
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#include <asm/cpu-regs.h>
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#include <asm/current.h>
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/* Forward declaration, a strange C thing */
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struct task_struct;
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struct mm_struct;
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/*
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* Default implementation of macro that returns current
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* instruction pointer ("program counter").
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*/
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#define current_text_addr() \
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({ \
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void *__pc; \
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asm("mov pc,%0" : "=a"(__pc)); \
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__pc; \
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})
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extern void get_mem_info(unsigned long *mem_base, unsigned long *mem_size);
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extern void show_registers(struct pt_regs *regs);
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/*
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* CPU type and hardware bug flags. Kept separately for each CPU.
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* Members of this structure are referenced in head.S, so think twice
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* before touching them. [mj]
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*/
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struct mn10300_cpuinfo {
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int type;
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unsigned long loops_per_jiffy;
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char hard_math;
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};
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extern struct mn10300_cpuinfo boot_cpu_data;
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#ifdef CONFIG_SMP
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#if CONFIG_NR_CPUS < 2 || CONFIG_NR_CPUS > 8
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# error Sorry, NR_CPUS should be 2 to 8
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#endif
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extern struct mn10300_cpuinfo cpu_data[];
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#define current_cpu_data cpu_data[smp_processor_id()]
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#else /* CONFIG_SMP */
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#define cpu_data &boot_cpu_data
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#define current_cpu_data boot_cpu_data
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#endif /* CONFIG_SMP */
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extern void identify_cpu(struct mn10300_cpuinfo *);
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extern void print_cpu_info(struct mn10300_cpuinfo *);
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extern void dodgy_tsc(void);
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#define cpu_relax() barrier()
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#define cpu_relax_yield() cpu_relax()
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#define cpu_relax_lowlatency() cpu_relax()
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/*
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* User space process size: 1.75GB (default).
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*/
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#define TASK_SIZE 0x70000000
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/*
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* Where to put the userspace stack by default
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*/
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#define STACK_TOP 0x70000000
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#define STACK_TOP_MAX STACK_TOP
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/* This decides where the kernel will search for a free chunk of vm
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* space during mmap's.
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*/
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#define TASK_UNMAPPED_BASE 0x30000000
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struct fpu_state_struct {
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unsigned long fs[32]; /* fpu registers */
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unsigned long fpcr; /* fpu control register */
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};
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struct thread_struct {
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struct pt_regs *uregs; /* userspace register frame */
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unsigned long pc; /* kernel PC */
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unsigned long sp; /* kernel SP */
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unsigned long a3; /* kernel FP */
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unsigned long wchan;
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unsigned long usp;
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unsigned long fpu_flags;
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#define THREAD_USING_FPU 0x00000001 /* T if this task is using the FPU */
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#define THREAD_HAS_FPU 0x00000002 /* T if this task owns the FPU right now */
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struct fpu_state_struct fpu_state;
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};
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#define INIT_THREAD \
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{ \
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.uregs = init_uregs, \
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.pc = 0, \
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.sp = 0, \
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.a3 = 0, \
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.wchan = 0, \
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}
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#define INIT_MMAP \
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{ &init_mm, 0, 0, NULL, PAGE_SHARED, VM_READ | VM_WRITE | VM_EXEC, 1, \
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NULL, NULL }
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/*
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* do necessary setup to start up a newly executed thread
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*/
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static inline void start_thread(struct pt_regs *regs,
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unsigned long new_pc, unsigned long new_sp)
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{
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regs->epsw = EPSW_nSL | EPSW_IE | EPSW_IM;
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regs->pc = new_pc;
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regs->sp = new_sp;
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}
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/* Free all resources held by a thread. */
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extern void release_thread(struct task_struct *);
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/*
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* Return saved PC of a blocked thread.
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*/
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extern unsigned long thread_saved_pc(struct task_struct *tsk);
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unsigned long get_wchan(struct task_struct *p);
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#define task_pt_regs(task) ((task)->thread.uregs)
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#define KSTK_EIP(task) (task_pt_regs(task)->pc)
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#define KSTK_ESP(task) (task_pt_regs(task)->sp)
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#define KSTK_TOP(info) \
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({ \
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(unsigned long)(info) + THREAD_SIZE; \
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})
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#define ARCH_HAS_PREFETCH
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#define ARCH_HAS_PREFETCHW
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static inline void prefetch(const void *x)
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{
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#ifdef CONFIG_MN10300_CACHE_ENABLED
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#ifdef CONFIG_MN10300_PROC_MN103E010
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asm volatile ("nop; nop; dcpf (%0)" : : "r"(x));
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#else
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asm volatile ("dcpf (%0)" : : "r"(x));
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#endif
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#endif
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}
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static inline void prefetchw(const void *x)
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{
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#ifdef CONFIG_MN10300_CACHE_ENABLED
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#ifdef CONFIG_MN10300_PROC_MN103E010
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asm volatile ("nop; nop; dcpf (%0)" : : "r"(x));
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#else
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asm volatile ("dcpf (%0)" : : "r"(x));
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#endif
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#endif
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}
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#endif /* _ASM_PROCESSOR_H */
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