1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_PREEMPT_H
3 #define __ASM_PREEMPT_H
6 #include <asm/percpu.h>
7 #include <linux/thread_info.h>
9 DECLARE_PER_CPU(int, __preempt_count
);
11 /* We use the MSB mostly because its available */
12 #define PREEMPT_NEED_RESCHED 0x80000000
15 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
16 * that a decrement hitting 0 means we can and should reschedule.
18 #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
21 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
22 * that think a non-zero value indicates we cannot preempt.
24 static __always_inline
int preempt_count(void)
26 return raw_cpu_read_4(__preempt_count
) & ~PREEMPT_NEED_RESCHED
;
29 static __always_inline
void preempt_count_set(int pc
)
34 old
= raw_cpu_read_4(__preempt_count
);
35 new = (old
& PREEMPT_NEED_RESCHED
) |
36 (pc
& ~PREEMPT_NEED_RESCHED
);
37 } while (raw_cpu_cmpxchg_4(__preempt_count
, old
, new) != old
);
41 * must be macros to avoid header recursion hell
43 #define init_task_preempt_count(p) do { } while (0)
45 #define init_idle_preempt_count(p, cpu) do { \
46 per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
50 * We fold the NEED_RESCHED bit into the preempt count such that
51 * preempt_enable() can decrement and test for needing to reschedule with a
54 * We invert the actual bit, so that when the decrement hits 0 we know we both
55 * need to resched (the bit is cleared) and can resched (no preempt count).
58 static __always_inline
void set_preempt_need_resched(void)
60 raw_cpu_and_4(__preempt_count
, ~PREEMPT_NEED_RESCHED
);
63 static __always_inline
void clear_preempt_need_resched(void)
65 raw_cpu_or_4(__preempt_count
, PREEMPT_NEED_RESCHED
);
68 static __always_inline
bool test_preempt_need_resched(void)
70 return !(raw_cpu_read_4(__preempt_count
) & PREEMPT_NEED_RESCHED
);
74 * The various preempt_count add/sub methods
77 static __always_inline
void __preempt_count_add(int val
)
79 raw_cpu_add_4(__preempt_count
, val
);
82 static __always_inline
void __preempt_count_sub(int val
)
84 raw_cpu_add_4(__preempt_count
, -val
);
88 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
89 * a decrement which hits zero means we have no preempt_count and should
92 static __always_inline
bool __preempt_count_dec_and_test(void)
94 return GEN_UNARY_RMWcc("decl", __preempt_count
, e
, __percpu_arg([var
]));
98 * Returns true when we need to resched and can (barring IRQ state).
100 static __always_inline
bool should_resched(int preempt_offset
)
102 return unlikely(raw_cpu_read_4(__preempt_count
) == preempt_offset
);
105 #ifdef CONFIG_PREEMPTION
106 extern asmlinkage
void preempt_schedule_thunk(void);
107 # define __preempt_schedule() \
108 asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT)
110 extern asmlinkage
void preempt_schedule(void);
111 extern asmlinkage
void preempt_schedule_notrace_thunk(void);
112 # define __preempt_schedule_notrace() \
113 asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT)
115 extern asmlinkage
void preempt_schedule_notrace(void);
118 #endif /* __ASM_PREEMPT_H */