1 #ifndef __ASM_PREEMPT_H
2 #define __ASM_PREEMPT_H
5 #include <asm/percpu.h>
6 #include <linux/thread_info.h>
10 * i386's current_thread_info() depends on ESP and for interrupt/exception
11 * stacks this doesn't yield the actual task thread_info.
13 * We hard rely on the fact that all the TIF_NEED_RESCHED bits are
14 * the same, therefore use the slightly more expensive version below.
16 #undef tif_need_resched
17 #define tif_need_resched() test_tsk_thread_flag(current, TIF_NEED_RESCHED)
20 DECLARE_PER_CPU(int, __preempt_count);
23 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
24 * that a decrement hitting 0 means we can and should reschedule.
26 #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
29 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
30 * that think a non-zero value indicates we cannot preempt.
32 static __always_inline int preempt_count(void)
34 return __this_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
37 static __always_inline void preempt_count_set(int pc)
39 __this_cpu_write_4(__preempt_count, pc);
43 * must be macros to avoid header recursion hell
45 #define task_preempt_count(p) \
46 (task_thread_info(p)->saved_preempt_count & ~PREEMPT_NEED_RESCHED)
48 #define init_task_preempt_count(p) do { \
49 task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \
52 #define init_idle_preempt_count(p, cpu) do { \
53 task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
54 per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
58 * We fold the NEED_RESCHED bit into the preempt count such that
59 * preempt_enable() can decrement and test for needing to reschedule with a
62 * We invert the actual bit, so that when the decrement hits 0 we know we both
63 * need to resched (the bit is cleared) and can resched (no preempt count).
66 static __always_inline void set_preempt_need_resched(void)
68 __this_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
71 static __always_inline void clear_preempt_need_resched(void)
73 __this_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
76 static __always_inline bool test_preempt_need_resched(void)
78 return !(__this_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
82 * The various preempt_count add/sub methods
85 static __always_inline void __preempt_count_add(int val)
87 __this_cpu_add_4(__preempt_count, val);
90 static __always_inline void __preempt_count_sub(int val)
92 __this_cpu_add_4(__preempt_count, -val);
96 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
97 * a decrement which hits zero means we have no preempt_count and should
100 static __always_inline bool __preempt_count_dec_and_test(void)
102 GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
106 * Returns true when we need to resched and can (barring IRQ state).
108 static __always_inline bool should_resched(void)
110 return unlikely(!__this_cpu_read_4(__preempt_count));
113 #ifdef CONFIG_PREEMPT
114 extern asmlinkage void ___preempt_schedule(void);
115 # define __preempt_schedule() asm ("call ___preempt_schedule")
116 extern asmlinkage void preempt_schedule(void);
117 # ifdef CONFIG_CONTEXT_TRACKING
118 extern asmlinkage void ___preempt_schedule_context(void);
119 # define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
123 #endif /* __ASM_PREEMPT_H */