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

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * Low-level task switching. This is based on information published in
   4 * the Processor Abstraction Layer and the System Abstraction Layer
   5 * manual.
   6 *
   7 * Copyright (C) 1998-2003 Hewlett-Packard Co
   8 *      David Mosberger-Tang <davidm@hpl.hp.com>
   9 * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com>
  10 * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
  11 */
  12#ifndef _ASM_IA64_SWITCH_TO_H
  13#define _ASM_IA64_SWITCH_TO_H
  14
  15#include <linux/percpu.h>
  16
  17struct task_struct;
  18
  19/*
  20 * Context switch from one thread to another.  If the two threads have
  21 * different address spaces, schedule() has already taken care of
  22 * switching to the new address space by calling switch_mm().
  23 *
  24 * Disabling access to the fph partition and the debug-register
  25 * context switch MUST be done before calling ia64_switch_to() since a
  26 * newly created thread returns directly to
  27 * ia64_ret_from_syscall_clear_r8.
  28 */
  29extern struct task_struct *ia64_switch_to (void *next_task);
  30
  31extern void ia64_save_extra (struct task_struct *task);
  32extern void ia64_load_extra (struct task_struct *task);
  33
  34#define IA64_HAS_EXTRA_STATE(t)                                                 \
  35        ((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID))
  36
  37#define __switch_to(prev,next,last) do {                                                         \
  38        if (IA64_HAS_EXTRA_STATE(prev))                                                          \
  39                ia64_save_extra(prev);                                                           \
  40        if (IA64_HAS_EXTRA_STATE(next))                                                          \
  41                ia64_load_extra(next);                                                           \
  42        ia64_psr(task_pt_regs(next))->dfh = !ia64_is_local_fpu_owner(next);                      \
  43        (last) = ia64_switch_to((next));                                                         \
  44} while (0)
  45
  46#ifdef CONFIG_SMP
  47/*
  48 * In the SMP case, we save the fph state when context-switching away from a thread that
  49 * modified fph.  This way, when the thread gets scheduled on another CPU, the CPU can
  50 * pick up the state from task->thread.fph, avoiding the complication of having to fetch
  51 * the latest fph state from another CPU.  In other words: eager save, lazy restore.
  52 */
  53# define switch_to(prev,next,last) do {                                         \
  54        if (ia64_psr(task_pt_regs(prev))->mfh && ia64_is_local_fpu_owner(prev)) {                               \
  55                ia64_psr(task_pt_regs(prev))->mfh = 0;                  \
  56                (prev)->thread.flags |= IA64_THREAD_FPH_VALID;                  \
  57                __ia64_save_fpu((prev)->thread.fph);                            \
  58        }                                                                       \
  59        __switch_to(prev, next, last);                                          \
  60        /* "next" in old context is "current" in new context */                 \
  61        if (unlikely((current->thread.flags & IA64_THREAD_MIGRATION) &&        \
  62                     (task_cpu(current) !=                                     \
  63                                      task_thread_info(current)->last_cpu))) { \
  64                task_thread_info(current)->last_cpu = task_cpu(current);       \
  65        }                                                                      \
  66} while (0)
  67#else
  68# define switch_to(prev,next,last)      __switch_to(prev, next, last)
  69#endif
  70
  71#endif /* _ASM_IA64_SWITCH_TO_H */
  72