1 /* 2 * Low-level task switching. This is based on information published in 3 * the Processor Abstraction Layer and the System Abstraction Layer 4 * manual. 5 * 6 * Copyright (C) 1998-2003 Hewlett-Packard Co 7 * David Mosberger-Tang <davidm@hpl.hp.com> 8 * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com> 9 * Copyright (C) 1999 Don Dugger <don.dugger@intel.com> 10 */ 11 #ifndef _ASM_IA64_SWITCH_TO_H 12 #define _ASM_IA64_SWITCH_TO_H 13 14 #include <linux/percpu.h> 15 16 struct task_struct; 17 18 /* 19 * Context switch from one thread to another. If the two threads have 20 * different address spaces, schedule() has already taken care of 21 * switching to the new address space by calling switch_mm(). 22 * 23 * Disabling access to the fph partition and the debug-register 24 * context switch MUST be done before calling ia64_switch_to() since a 25 * newly created thread returns directly to 26 * ia64_ret_from_syscall_clear_r8. 27 */ 28 extern struct task_struct *ia64_switch_to (void *next_task); 29 30 extern void ia64_save_extra (struct task_struct *task); 31 extern void ia64_load_extra (struct task_struct *task); 32 33 #ifdef CONFIG_PERFMON 34 DECLARE_PER_CPU(unsigned long, pfm_syst_info); 35 # define PERFMON_IS_SYSWIDE() (__this_cpu_read(pfm_syst_info) & 0x1) 36 #else 37 # define PERFMON_IS_SYSWIDE() (0) 38 #endif 39 40 #define IA64_HAS_EXTRA_STATE(t) \ 41 ((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID) \ 42 || PERFMON_IS_SYSWIDE()) 43 44 #define __switch_to(prev,next,last) do { \ 45 if (IA64_HAS_EXTRA_STATE(prev)) \ 46 ia64_save_extra(prev); \ 47 if (IA64_HAS_EXTRA_STATE(next)) \ 48 ia64_load_extra(next); \ 49 ia64_psr(task_pt_regs(next))->dfh = !ia64_is_local_fpu_owner(next); \ 50 (last) = ia64_switch_to((next)); \ 51 } while (0) 52 53 #ifdef CONFIG_SMP 54 /* 55 * In the SMP case, we save the fph state when context-switching away from a thread that 56 * modified fph. This way, when the thread gets scheduled on another CPU, the CPU can 57 * pick up the state from task->thread.fph, avoiding the complication of having to fetch 58 * the latest fph state from another CPU. In other words: eager save, lazy restore. 59 */ 60 # define switch_to(prev,next,last) do { \ 61 if (ia64_psr(task_pt_regs(prev))->mfh && ia64_is_local_fpu_owner(prev)) { \ 62 ia64_psr(task_pt_regs(prev))->mfh = 0; \ 63 (prev)->thread.flags |= IA64_THREAD_FPH_VALID; \ 64 __ia64_save_fpu((prev)->thread.fph); \ 65 } \ 66 __switch_to(prev, next, last); \ 67 /* "next" in old context is "current" in new context */ \ 68 if (unlikely((current->thread.flags & IA64_THREAD_MIGRATION) && \ 69 (task_cpu(current) != \ 70 task_thread_info(current)->last_cpu))) { \ 71 platform_migrate(current); \ 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