arch/mips/include/asm/switch_to.h

   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
  21 struct 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  */
  32 extern asmlinkage struct task_struct *resume(struct task_struct *prev,
  33                 struct task_struct *next, struct thread_info *next_ti);
  34
  35 extern unsigned int ll_bit;
  36 extern 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)                                 \
  53 do {                                                                    \
  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)                                          \
  88 do {                                                                    \
  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)                                     \
 106 do {                                                                    \
 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 */