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
16struct 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 */
28extern struct task_struct *ia64_switch_to (void *next_task);
29
30extern void ia64_save_extra (struct task_struct *task);
31extern 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