switch_to.h

Go to the documentation of this file.

/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#ifndef _ASM_TILE_SWITCH_TO_H
#define _ASM_TILE_SWITCH_TO_H

#include <arch/sim_def.h>

/*
 * switch_to(n) should switch tasks to task nr n, first
 * checking that n isn't the current task, in which case it does nothing.
 * The number of callee-saved registers saved on the kernel stack
 * is defined here for use in copy_thread() and must agree with __switch_to().
 */
#define CALLEE_SAVED_FIRST_REG 30
#define CALLEE_SAVED_REGS_COUNT 24   /* r30 to r52, plus an empty to align */

#ifndef __ASSEMBLY__

struct task_struct;

/*
 * Pause the DMA engine and static network before task switching.
 */
#define prepare_arch_switch(next) _prepare_arch_switch(next)
void _prepare_arch_switch(struct task_struct *next);

struct task_struct;
#define switch_to(prev, next, last) ((last) = _switch_to((prev), (next)))
extern struct task_struct *_switch_to(struct task_struct *prev,
                      struct task_struct *next);

/* Helper function for _switch_to(). */
extern struct task_struct *__switch_to(struct task_struct *prev,
                       struct task_struct *next,
                       unsigned long new_system_save_k_0);

/* Address that switched-away from tasks are at. */
extern unsigned long get_switch_to_pc(void);

/*
 * Kernel threads can check to see if they need to migrate their
 * stack whenever they return from a context switch; for user
 * threads, we defer until they are returning to user-space.
 */
#define finish_arch_switch(prev) do {                                     \
    if (unlikely((prev)->state == TASK_DEAD))                         \
        __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_EXIT |       \
            ((prev)->pid << _SIM_CONTROL_OPERATOR_BITS));     \
    __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_SWITCH |             \
        (current->pid << _SIM_CONTROL_OPERATOR_BITS));            \
    if (current->mm == NULL && !kstack_hash &&                        \
        current_thread_info()->homecache_cpu != smp_processor_id())   \
        homecache_migrate_kthread();                              \
} while (0)

/* Support function for forking a new task. */
void ret_from_fork(void);

/* Called from ret_from_fork() when a new process starts up. */
struct task_struct *sim_notify_fork(struct task_struct *prev);

#endif /* !__ASSEMBLY__ */

#endif /* _ASM_TILE_SWITCH_TO_H */