1 #ifndef __LINUX_PREEMPT_H

     2 #define __LINUX_PREEMPT_H

     3 

     4 /*

     5  * include/linux/preempt.h - macros for accessing and manipulating

     6  * preempt_count (used for kernel preemption, interrupt count, etc.)

     7  */

     8 

     9 #include <linux/thread_info.h>

    10 #include <linux/linkage.h>

    11 #include <linux/list.h>

    12 

    13 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)

    14   extern void add_preempt_count(int val);

    15   extern void sub_preempt_count(int val);

    16 #else

    17 # define add_preempt_count(val)	do { preempt_count() += (val); } while (0)

    18 # define sub_preempt_count(val)	do { preempt_count() -= (val); } while (0)

    19 #endif

    20 

    21 #define inc_preempt_count() add_preempt_count(1)

    22 #define dec_preempt_count() sub_preempt_count(1)

    23 

    24 #define preempt_count()	(current_thread_info()->preempt_count)

    25 

    26 #ifdef CONFIG_PREEMPT

    27 

    28 asmlinkage void preempt_schedule(void);

    29 

    30 #define preempt_disable() \

    31 do { \

    32 	inc_preempt_count(); \

    33 	barrier(); \

    34 } while (0)

    35 

    36 #define preempt_enable_no_resched() \

    37 do { \

    38 	barrier(); \

    39 	dec_preempt_count(); \

    40 } while (0)

    41 

    42 #define preempt_check_resched() \

    43 do { \

    44 	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \

    45 		preempt_schedule(); \

    46 } while (0)

    47 

    48 #define preempt_enable() \

    49 do { \

    50 	preempt_enable_no_resched(); \

    51 	barrier(); \

    52 	preempt_check_resched(); \

    53 } while (0)

    54 

    55 /* For debugging and tracer internals only! */

    56 #define add_preempt_count_notrace(val)			\

    57 	do { preempt_count() += (val); } while (0)

    58 #define sub_preempt_count_notrace(val)			\

    59 	do { preempt_count() -= (val); } while (0)

    60 #define inc_preempt_count_notrace() add_preempt_count_notrace(1)

    61 #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)

    62 

    63 #define preempt_disable_notrace() \

    64 do { \

    65 	inc_preempt_count_notrace(); \

    66 	barrier(); \

    67 } while (0)

    68 

    69 #define preempt_enable_no_resched_notrace() \

    70 do { \

    71 	barrier(); \

    72 	dec_preempt_count_notrace(); \

    73 } while (0)

    74 

    75 /* preempt_check_resched is OK to trace */

    76 #define preempt_enable_notrace() \

    77 do { \

    78 	preempt_enable_no_resched_notrace(); \

    79 	barrier(); \

    80 	preempt_check_resched(); \

    81 } while (0)

    82 

    83 #else

    84 

    85 #define preempt_disable()		do { } while (0)

    86 #define preempt_enable_no_resched()	do { } while (0)

    87 #define preempt_enable()		do { } while (0)

    88 #define preempt_check_resched()		do { } while (0)

    89 

    90 #define preempt_disable_notrace()		do { } while (0)

    91 #define preempt_enable_no_resched_notrace()	do { } while (0)

    92 #define preempt_enable_notrace()		do { } while (0)

    93 

    94 #endif

    95 

    96 #ifdef CONFIG_PREEMPT_NOTIFIERS

    97 

    98 struct preempt_notifier;

    99 

   100 /**

   101  * preempt_ops - notifiers called when a task is preempted and rescheduled

   102  * @sched_in: we're about to be rescheduled:

   103  *    notifier: struct preempt_notifier for the task being scheduled

   104  *    cpu:  cpu we're scheduled on

   105  * @sched_out: we've just been preempted

   106  *    notifier: struct preempt_notifier for the task being preempted

   107  *    next: the task that's kicking us out

   108  */

   109 struct preempt_ops {

   110 	void (*sched_in)(struct preempt_notifier *notifier, int cpu);

   111 	void (*sched_out)(struct preempt_notifier *notifier,

   112 			  struct task_struct *next);

   113 };

   114 

   115 /**

   116  * preempt_notifier - key for installing preemption notifiers

   117  * @link: internal use

   118  * @ops: defines the notifier functions to be called

   119  *

   120  * Usually used in conjunction with container_of().

   121  */

   122 struct preempt_notifier {

   123 	struct hlist_node link;

   124 	struct preempt_ops *ops;

   125 };

   126 

   127 void preempt_notifier_register(struct preempt_notifier *notifier);

   128 void preempt_notifier_unregister(struct preempt_notifier *notifier);

   129 

   130 static inline void preempt_notifier_init(struct preempt_notifier *notifier,

   131 				     struct preempt_ops *ops)

   132 {

   133 	INIT_HLIST_NODE(&notifier->link);

   134 	notifier->ops = ops;

   135 }

   136 

   137 #endif

   138 

   139 #endif /* __LINUX_PREEMPT_H */