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>
139 lines
3.6 KiB
C
139 lines
3.6 KiB
C
/*
|
|
* Port on Texas Instruments TMS320C6x architecture
|
|
*
|
|
* Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
|
|
* Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
|
|
*
|
|
* Updated for 2.6.34: Mark Salter <msalter@redhat.com>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
#ifndef _ASM_C6X_PROCESSOR_H
|
|
#define _ASM_C6X_PROCESSOR_H
|
|
|
|
#include <asm/ptrace.h>
|
|
#include <asm/page.h>
|
|
#include <asm/current.h>
|
|
|
|
/*
|
|
* Default implementation of macro that returns current
|
|
* instruction pointer ("program counter").
|
|
*/
|
|
#define current_text_addr() \
|
|
({ \
|
|
void *__pc; \
|
|
asm("mvc .S2 pce1,%0\n" : "=b"(__pc)); \
|
|
__pc; \
|
|
})
|
|
|
|
/*
|
|
* User space process size. This is mostly meaningless for NOMMU
|
|
* but some C6X processors may have RAM addresses up to 0xFFFFFFFF.
|
|
* Since calls like mmap() can return an address or an error, we
|
|
* have to allow room for error returns when code does something
|
|
* like:
|
|
*
|
|
* addr = do_mmap(...)
|
|
* if ((unsigned long)addr >= TASK_SIZE)
|
|
* ... its an error code, not an address ...
|
|
*
|
|
* Here, we allow for 4096 error codes which means we really can't
|
|
* use the last 4K page on systems with RAM extending all the way
|
|
* to the end of the 32-bit address space.
|
|
*/
|
|
#define TASK_SIZE 0xFFFFF000
|
|
|
|
/*
|
|
* This decides where the kernel will search for a free chunk of vm
|
|
* space during mmap's. We won't be using it
|
|
*/
|
|
#define TASK_UNMAPPED_BASE 0
|
|
|
|
struct thread_struct {
|
|
unsigned long long b15_14;
|
|
unsigned long long a15_14;
|
|
unsigned long long b13_12;
|
|
unsigned long long a13_12;
|
|
unsigned long long b11_10;
|
|
unsigned long long a11_10;
|
|
unsigned long long ricl_icl;
|
|
unsigned long usp; /* user stack pointer */
|
|
unsigned long pc; /* kernel pc */
|
|
unsigned long wchan;
|
|
};
|
|
|
|
#define INIT_THREAD \
|
|
{ \
|
|
.usp = 0, \
|
|
.wchan = 0, \
|
|
}
|
|
|
|
#define INIT_MMAP { \
|
|
&init_mm, 0, 0, NULL, PAGE_SHARED, VM_READ | VM_WRITE | VM_EXEC, 1, \
|
|
NULL, NULL }
|
|
|
|
#define task_pt_regs(task) \
|
|
((struct pt_regs *)(THREAD_START_SP + task_stack_page(task)) - 1)
|
|
|
|
#define alloc_kernel_stack() __get_free_page(GFP_KERNEL)
|
|
#define free_kernel_stack(page) free_page((page))
|
|
|
|
|
|
/* Forward declaration, a strange C thing */
|
|
struct task_struct;
|
|
|
|
extern void start_thread(struct pt_regs *regs, unsigned int pc,
|
|
unsigned long usp);
|
|
|
|
/* Free all resources held by a thread. */
|
|
static inline void release_thread(struct task_struct *dead_task)
|
|
{
|
|
}
|
|
|
|
#define copy_segments(tsk, mm) do { } while (0)
|
|
#define release_segments(mm) do { } while (0)
|
|
|
|
/*
|
|
* saved PC of a blocked thread.
|
|
*/
|
|
#define thread_saved_pc(tsk) (task_pt_regs(tsk)->pc)
|
|
|
|
/*
|
|
* saved kernel SP and DP of a blocked thread.
|
|
*/
|
|
#ifdef _BIG_ENDIAN
|
|
#define thread_saved_ksp(tsk) \
|
|
(*(unsigned long *)&(tsk)->thread.b15_14)
|
|
#define thread_saved_dp(tsk) \
|
|
(*(((unsigned long *)&(tsk)->thread.b15_14) + 1))
|
|
#else
|
|
#define thread_saved_ksp(tsk) \
|
|
(*(((unsigned long *)&(tsk)->thread.b15_14) + 1))
|
|
#define thread_saved_dp(tsk) \
|
|
(*(unsigned long *)&(tsk)->thread.b15_14)
|
|
#endif
|
|
|
|
extern unsigned long get_wchan(struct task_struct *p);
|
|
|
|
#define KSTK_EIP(task) (task_pt_regs(task)->pc)
|
|
#define KSTK_ESP(task) (task_pt_regs(task)->sp)
|
|
|
|
#define cpu_relax() do { } while (0)
|
|
#define cpu_relax_yield() cpu_relax()
|
|
#define cpu_relax_lowlatency() cpu_relax()
|
|
|
|
extern const struct seq_operations cpuinfo_op;
|
|
|
|
/* Reset the board */
|
|
#define HARD_RESET_NOW()
|
|
|
|
extern unsigned int c6x_core_freq;
|
|
|
|
|
|
extern void (*c6x_restart)(void);
|
|
extern void (*c6x_halt)(void);
|
|
|
|
#endif /* ASM_C6X_PROCESSOR_H */
|