LXR linux/arch/ia64/include/asm/switch

   1/*
   2 * Low-level task switching. This is based on information published in
   3 * the Processor Abstraction Layer and the System Abstraction Layer
   4 * manual.
   5 *
   6 * Copyright (C) 1998-2003 Hewlett-Packard Co
   7 *      David Mosberger-Tang <davidm@hpl.hp.com>
   8 * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com>
   9 * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
  10 */
  11#ifndef _ASM_IA64_SWITCH_TO_H
  12#define _ASM_IA64_SWITCH_TO_H
  13
  14#include <linux/percpu.h>
  15
  16struct task_struct;
  17
  18/*
  19 * Context switch from one thread to another.  If the two threads have
  20 * different address spaces, schedule() has already taken care of
  21 * switching to the new address space by calling switch_mm().
  22 *
  23 * Disabling access to the fph partition and the debug-register
  24 * context switch MUST be done before calling ia64_switch_to() since a
  25 * newly created thread returns directly to
  26 * ia64_ret_from_syscall_clear_r8.
  27 */
  28extern struct task_struct *ia64_switch_to (void *next_task);
  29
  30extern void ia64_save_extra (struct task_struct *task);
  31extern void ia64_load_extra (struct task_struct *task);
  32
  33#ifdef CONFIG_PERFMON
  34  DECLARE_PER_CPU(unsigned long, pfm_syst_info);
  35# define PERFMON_IS_SYSWIDE() (__get_cpu_var(pfm_syst_info) & 0x1)
  36#else
  37# define PERFMON_IS_SYSWIDE() (0)
  38#endif
  39
  40#define IA64_HAS_EXTRA_STATE(t)                                                 \
  41        ((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID)       \
  42         || PERFMON_IS_SYSWIDE())
  43
  44#define __switch_to(prev,next,last) do {                                                         \
  45        if (IA64_HAS_EXTRA_STATE(prev))                                                          \
  46                ia64_save_extra(prev);                                                           \
  47        if (IA64_HAS_EXTRA_STATE(next))                                                          \
  48                ia64_load_extra(next);                                                           \
  49        ia64_psr(task_pt_regs(next))->dfh = !ia64_is_local_fpu_owner(next);                      \
  50        (last) = ia64_switch_to((next));                                                         \
  51} while (0)
  52
  53#ifdef CONFIG_SMP
  54/*
  55 * In the SMP case, we save the fph state when context-switching away from a thread that
  56 * modified fph.  This way, when the thread gets scheduled on another CPU, the CPU can
  57 * pick up the state from task->thread.fph, avoiding the complication of having to fetch
  58 * the latest fph state from another CPU.  In other words: eager save, lazy restore.
  59 */
  60# define switch_to(prev,next,last) do {                                         \
  61        if (ia64_psr(task_pt_regs(prev))->mfh && ia64_is_local_fpu_owner(prev)) {                               \
  62                ia64_psr(task_pt_regs(prev))->mfh = 0;                  \
  63                (prev)->thread.flags |= IA64_THREAD_FPH_VALID;                  \
  64                __ia64_save_fpu((prev)->thread.fph);                            \
  65        }                                                                       \
  66        __switch_to(prev, next, last);                                          \
  67        /* "next" in old context is "current" in new context */                 \
  68        if (unlikely((current->thread.flags & IA64_THREAD_MIGRATION) &&        \
  69                     (task_cpu(current) !=                                     \
  70                                      task_thread_info(current)->last_cpu))) { \
  71                platform_migrate(current);                                     \
  72                task_thread_info(current)->last_cpu = task_cpu(current);       \
  73        }                                                                      \
  74} while (0)
  75#else
  76# define switch_to(prev,next,last)      __switch_to(prev, next, last)
  77#endif
  78
  79#endif /* _ASM_IA64_SWITCH_TO_H */
  80