LXR linux/arch/mips/include/asm/switch

   1/*
   2 * This file is subject to the terms and conditions of the GNU General Public
   3 * License.  See the file "COPYING" in the main directory of this archive
   4 * for more details.
   5 *
   6 * Copyright (C) 1994, 95, 96, 97, 98, 99, 2003, 06 by Ralf Baechle
   7 * Copyright (C) 1996 by Paul M. Antoine
   8 * Copyright (C) 1999 Silicon Graphics
   9 * Kevin D. Kissell, kevink@mips.org and Carsten Langgaard, carstenl@mips.com
  10 * Copyright (C) 2000 MIPS Technologies, Inc.
  11 */
  12#ifndef _ASM_SWITCH_TO_H
  13#define _ASM_SWITCH_TO_H
  14
  15#include <asm/cpu-features.h>
  16#include <asm/watch.h>
  17#include <asm/dsp.h>
  18#include <asm/cop2.h>
  19#include <asm/fpu.h>
  20
  21struct task_struct;
  22
  23/**
  24 * resume - resume execution of a task
  25 * @prev:       The task previously executed.
  26 * @next:       The task to begin executing.
  27 * @next_ti:    task_thread_info(next).
  28 *
  29 * This function is used whilst scheduling to save the context of prev & load
  30 * the context of next. Returns prev.
  31 */
  32extern asmlinkage struct task_struct *resume(struct task_struct *prev,
  33                struct task_struct *next, struct thread_info *next_ti);
  34
  35extern unsigned int ll_bit;
  36extern struct task_struct *ll_task;
  37
  38#ifdef CONFIG_MIPS_MT_FPAFF
  39
  40/*
  41 * Handle the scheduler resume end of FPU affinity management.  We do this
  42 * inline to try to keep the overhead down. If we have been forced to run on
  43 * a "CPU" with an FPU because of a previous high level of FP computation,
  44 * but did not actually use the FPU during the most recent time-slice (CU1
  45 * isn't set), we undo the restriction on cpus_allowed.
  46 *
  47 * We're not calling set_cpus_allowed() here, because we have no need to
  48 * force prompt migration - we're already switching the current CPU to a
  49 * different thread.
  50 */
  51
  52#define __mips_mt_fpaff_switch_to(prev)                                 \
  53do {                                                                    \
  54        struct thread_info *__prev_ti = task_thread_info(prev);         \
  55                                                                        \
  56        if (cpu_has_fpu &&                                              \
  57            test_ti_thread_flag(__prev_ti, TIF_FPUBOUND) &&             \
  58            (!(KSTK_STATUS(prev) & ST0_CU1))) {                         \
  59                clear_ti_thread_flag(__prev_ti, TIF_FPUBOUND);          \
  60                prev->cpus_allowed = prev->thread.user_cpus_allowed;    \
  61        }                                                               \
  62        next->thread.emulated_fp = 0;                                   \
  63} while(0)
  64
  65#else
  66#define __mips_mt_fpaff_switch_to(prev) do { (void) (prev); } while (0)
  67#endif
  68
  69/*
  70 * Clear LLBit during context switches on MIPSr6 such that eretnc can be used
  71 * unconditionally when returning to userland in entry.S.
  72 */
  73#define __clear_r6_hw_ll_bit() do {                                     \
  74        if (cpu_has_mips_r6)                                            \
  75                write_c0_lladdr(0);                                     \
  76} while (0)
  77
  78#define __clear_software_ll_bit() do {                                  \
  79        if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc)       \
  80                ll_bit = 0;                                             \
  81} while (0)
  82
  83/*
  84 * Check FCSR for any unmasked exceptions pending set with `ptrace',
  85 * clear them and send a signal.
  86 */
  87#define __sanitize_fcr31(next)                                          \
  88do {                                                                    \
  89        unsigned long fcr31 = mask_fcr31_x(next->thread.fpu.fcr31);     \
  90        void __user *pc;                                                \
  91                                                                        \
  92        if (unlikely(fcr31)) {                                          \
  93                pc = (void __user *)task_pt_regs(next)->cp0_epc;        \
  94                next->thread.fpu.fcr31 &= ~fcr31;                       \
  95                force_fcr31_sig(fcr31, pc, next);                       \
  96        }                                                               \
  97} while (0)
  98
  99/*
 100 * For newly created kernel threads switch_to() will return to
 101 * ret_from_kernel_thread, newly created user threads to ret_from_fork.
 102 * That is, everything following resume() will be skipped for new threads.
 103 * So everything that matters to new threads should be placed before resume().
 104 */
 105#define switch_to(prev, next, last)                                     \
 106do {                                                                    \
 107        __mips_mt_fpaff_switch_to(prev);                                \
 108        lose_fpu_inatomic(1, prev);                                     \
 109        if (tsk_used_math(next))                                        \
 110                __sanitize_fcr31(next);                                 \
 111        if (cpu_has_dsp) {                                              \
 112                __save_dsp(prev);                                       \
 113                __restore_dsp(next);                                    \
 114        }                                                               \
 115        if (cop2_present) {                                             \
 116                set_c0_status(ST0_CU2);                                 \
 117                if ((KSTK_STATUS(prev) & ST0_CU2)) {                    \
 118                        if (cop2_lazy_restore)                          \
 119                                KSTK_STATUS(prev) &= ~ST0_CU2;          \
 120                        cop2_save(prev);                                \
 121                }                                                       \
 122                if (KSTK_STATUS(next) & ST0_CU2 &&                      \
 123                    !cop2_lazy_restore) {                               \
 124                        cop2_restore(next);                             \
 125                }                                                       \
 126                clear_c0_status(ST0_CU2);                               \
 127        }                                                               \
 128        __clear_r6_hw_ll_bit();                                         \
 129        __clear_software_ll_bit();                                      \
 130        if (cpu_has_userlocal)                                          \
 131                write_c0_userlocal(task_thread_info(next)->tp_value);   \
 132        __restore_watch(next);                                          \
 133        (last) = resume(prev, next, task_thread_info(next));            \
 134} while (0)
 135
 136#endif /* _ASM_SWITCH_TO_H */
 137