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 #ifdef CONFIG_PERFMON 35 DECLARE_PER_CPU(unsigned long, pfm_syst_info); 36 # define PERFMON_IS_SYSWIDE() (__this_cpu_read(pfm_syst_info) & 0x1) 37 #else 38 # define PERFMON_IS_SYSWIDE() (0) 39 #endif 40 41 #define IA64_HAS_EXTRA_STATE(t) \ 42 ((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID) \ 43 || PERFMON_IS_SYSWIDE()) 44 45 #define __switch_to(prev,next,last) do { \ 46 if (IA64_HAS_EXTRA_STATE(prev)) \ 47 ia64_save_extra(prev); \ 48 if (IA64_HAS_EXTRA_STATE(next)) \ 49 ia64_load_extra(next); \ 50 ia64_psr(task_pt_regs(next))->dfh = !ia64_is_local_fpu_owner(next); \ 51 (last) = ia64_switch_to((next)); \ 52 } while (0) 53 54 #ifdef CONFIG_SMP 55 /* 56 * In the SMP case, we save the fph state when context-switching away from a thread that 57 * modified fph. This way, when the thread gets scheduled on another CPU, the CPU can 58 * pick up the state from task->thread.fph, avoiding the complication of having to fetch 59 * the latest fph state from another CPU. In other words: eager save, lazy restore. 60 */ 61 # define switch_to(prev,next,last) do { \ 62 if (ia64_psr(task_pt_regs(prev))->mfh && ia64_is_local_fpu_owner(prev)) { \ 63 ia64_psr(task_pt_regs(prev))->mfh = 0; \ 64 (prev)->thread.flags |= IA64_THREAD_FPH_VALID; \ 65 __ia64_save_fpu((prev)->thread.fph); \ 66 } \ 67 __switch_to(prev, next, last); \ 68 /* "next" in old context is "current" in new context */ \ 69 if (unlikely((current->thread.flags & IA64_THREAD_MIGRATION) && \ 70 (task_cpu(current) != \ 71 task_thread_info(current)->last_cpu))) { \ 72 task_thread_info(current)->last_cpu = task_cpu(current); \ 73 } \ 74 } while (0) 75 #else 76 # define switch_to(prev,next,last) __switch_to(prev, next, last) 77 #endif 78 79 #endif /* _ASM_IA64_SWITCH_TO_H */ 80