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 17 struct 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 */ 29 extern struct task_struct *ia64_switch_to (void *next_task); 30 31 extern void ia64_save_extra (struct task_struct *task); 32 extern 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