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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Low-level task switching. This is based on information published in
* the Processor Abstraction Layer and the System Abstraction Layer
* manual.
*
* Copyright (C) 1998-2003 Hewlett-Packard Co
* David Mosberger-Tang <[email protected]>
* Copyright (C) 1999 Asit Mallick <[email protected]>
* Copyright (C) 1999 Don Dugger <[email protected]>
*/
#ifndef _ASM_IA64_SWITCH_TO_H
#define _ASM_IA64_SWITCH_TO_H
#include <linux/percpu.h>
struct task_struct;
/*
* Context switch from one thread to another. If the two threads have
* different address spaces, schedule() has already taken care of
* switching to the new address space by calling switch_mm().
*
* Disabling access to the fph partition and the debug-register
* context switch MUST be done before calling ia64_switch_to() since a
* newly created thread returns directly to
* ia64_ret_from_syscall_clear_r8.
*/
extern struct task_struct *ia64_switch_to (void *next_task);
extern void ia64_save_extra (struct task_struct *task);
extern void ia64_load_extra (struct task_struct *task);
#define IA64_HAS_EXTRA_STATE(t) \
((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID))
#define __switch_to(prev,next,last) do { \
if (IA64_HAS_EXTRA_STATE(prev)) \
ia64_save_extra(prev); \
if (IA64_HAS_EXTRA_STATE(next)) \
ia64_load_extra(next); \
ia64_psr(task_pt_regs(next))->dfh = !ia64_is_local_fpu_owner(next); \
(last) = ia64_switch_to((next)); \
} while (0)
#ifdef CONFIG_SMP
/*
* In the SMP case, we save the fph state when context-switching away from a thread that
* modified fph. This way, when the thread gets scheduled on another CPU, the CPU can
* pick up the state from task->thread.fph, avoiding the complication of having to fetch
* the latest fph state from another CPU. In other words: eager save, lazy restore.
*/
# define switch_to(prev,next,last) do { \
if (ia64_psr(task_pt_regs(prev))->mfh && ia64_is_local_fpu_owner(prev)) { \
ia64_psr(task_pt_regs(prev))->mfh = 0; \
(prev)->thread.flags |= IA64_THREAD_FPH_VALID; \
__ia64_save_fpu((prev)->thread.fph); \
} \
__switch_to(prev, next, last); \
/* "next" in old context is "current" in new context */ \
if (unlikely((current->thread.flags & IA64_THREAD_MIGRATION) && \
(task_cpu(current) != \
task_thread_info(current)->last_cpu))) { \
task_thread_info(current)->last_cpu = task_cpu(current); \
} \
} while (0)
#else
# define switch_to(prev,next,last) __switch_to(prev, next, last)
#endif
#endif /* _ASM_IA64_SWITCH_TO_H */
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