1#ifndef __ASM_PREEMPT_H
2#define __ASM_PREEMPT_H
3
4#include <asm/rmwcc.h>
5#include <asm/percpu.h>
6#include <linux/thread_info.h>
7
8DECLARE_PER_CPU(int, __preempt_count);
9
10/*
11 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
12 * that a decrement hitting 0 means we can and should reschedule.
13 */
14#define PREEMPT_ENABLED	(0 + PREEMPT_NEED_RESCHED)
15
16/*
17 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
18 * that think a non-zero value indicates we cannot preempt.
19 */
20static __always_inline int preempt_count(void)
21{
22	return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
23}
24
25static __always_inline void preempt_count_set(int pc)
26{
27	raw_cpu_write_4(__preempt_count, pc);
28}
29
30/*
31 * must be macros to avoid header recursion hell
32 */
33#define init_task_preempt_count(p) do { \
34	task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \
35} while (0)
36
37#define init_idle_preempt_count(p, cpu) do { \
38	task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
39	per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
40} while (0)
41
42/*
43 * We fold the NEED_RESCHED bit into the preempt count such that
44 * preempt_enable() can decrement and test for needing to reschedule with a
45 * single instruction.
46 *
47 * We invert the actual bit, so that when the decrement hits 0 we know we both
48 * need to resched (the bit is cleared) and can resched (no preempt count).
49 */
50
51static __always_inline void set_preempt_need_resched(void)
52{
53	raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
54}
55
56static __always_inline void clear_preempt_need_resched(void)
57{
58	raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
59}
60
61static __always_inline bool test_preempt_need_resched(void)
62{
63	return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
64}
65
66/*
67 * The various preempt_count add/sub methods
68 */
69
70static __always_inline void __preempt_count_add(int val)
71{
72	raw_cpu_add_4(__preempt_count, val);
73}
74
75static __always_inline void __preempt_count_sub(int val)
76{
77	raw_cpu_add_4(__preempt_count, -val);
78}
79
80/*
81 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
82 * a decrement which hits zero means we have no preempt_count and should
83 * reschedule.
84 */
85static __always_inline bool __preempt_count_dec_and_test(void)
86{
87	GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
88}
89
90/*
91 * Returns true when we need to resched and can (barring IRQ state).
92 */
93static __always_inline bool should_resched(int preempt_offset)
94{
95	return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
96}
97
98#ifdef CONFIG_PREEMPT
99  extern asmlinkage void ___preempt_schedule(void);
100# define __preempt_schedule() asm ("call ___preempt_schedule")
101  extern asmlinkage void preempt_schedule(void);
102# ifdef CONFIG_CONTEXT_TRACKING
103    extern asmlinkage void ___preempt_schedule_context(void);
104#   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
105    extern asmlinkage void preempt_schedule_context(void);
106# endif
107#endif
108
109#endif /* __ASM_PREEMPT_H */
110