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/linkage.h>
10 #include <linux/list.h>
11
12 /*
13 * We put the hardirq and softirq counter into the preemption
14 * counter. The bitmask has the following meaning:
15 *
16 * - bits 0-7 are the preemption count (max preemption depth: 256)
17 * - bits 8-15 are the softirq count (max # of softirqs: 256)
18 *
19 * The hardirq count could in theory be the same as the number of
20 * interrupts in the system, but we run all interrupt handlers with
21 * interrupts disabled, so we cannot have nesting interrupts. Though
22 * there are a few palaeontologic drivers which reenable interrupts in
23 * the handler, so we need more than one bit here.
24 *
25 * PREEMPT_MASK: 0x000000ff
26 * SOFTIRQ_MASK: 0x0000ff00
27 * HARDIRQ_MASK: 0x000f0000
28 * NMI_MASK: 0x00100000
29 * PREEMPT_NEED_RESCHED: 0x80000000
30 */
31 #define PREEMPT_BITS 8
32 #define SOFTIRQ_BITS 8
33 #define HARDIRQ_BITS 4
34 #define NMI_BITS 1
35
36 #define PREEMPT_SHIFT 0
37 #define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS)
38 #define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS)
39 #define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS)
40
41 #define __IRQ_MASK(x) ((1UL << (x))-1)
42
43 #define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT)
44 #define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT)
45 #define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT)
46 #define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT)
47
48 #define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT)
49 #define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT)
50 #define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT)
51 #define NMI_OFFSET (1UL << NMI_SHIFT)
52
53 #define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET)
54
55 /* We use the MSB mostly because its available */
56 #define PREEMPT_NEED_RESCHED 0x80000000
57
58 /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */
59 #include <asm/preempt.h>
60
61 #define hardirq_count() (preempt_count() & HARDIRQ_MASK)
62 #define softirq_count() (preempt_count() & SOFTIRQ_MASK)
63 #define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
64 | NMI_MASK))
65
66 /*
67 * Are we doing bottom half or hardware interrupt processing?
68 *
69 * in_irq() - We're in (hard) IRQ context
70 * in_softirq() - We have BH disabled, or are processing softirqs
71 * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled
72 * in_serving_softirq() - We're in softirq context
73 * in_nmi() - We're in NMI context
74 * in_task() - We're in task context
75 *
76 * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really
77 * should not be used in new code.
78 */
79 #define in_irq() (hardirq_count())
80 #define in_softirq() (softirq_count())
81 #define in_interrupt() (irq_count())
82 #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET)
83 #define in_nmi() (preempt_count() & NMI_MASK)
84 #define in_task() (!(preempt_count() & \
85 (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
86
87 /*
88 * The preempt_count offset after preempt_disable();
89 */
90 #if defined(CONFIG_PREEMPT_COUNT)
91 # define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET
92 #else
93 # define PREEMPT_DISABLE_OFFSET 0
94 #endif
95
96 /*
97 * The preempt_count offset after spin_lock()
98 */
99 #define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET
100
101 /*
102 * The preempt_count offset needed for things like:
103 *
104 * spin_lock_bh()
105 *
106 * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and
107 * softirqs, such that unlock sequences of:
108 *
109 * spin_unlock();
110 * local_bh_enable();
111 *
112 * Work as expected.
113 */
114 #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET)
115
116 /*
117 * Are we running in atomic context? WARNING: this macro cannot
118 * always detect atomic context; in particular, it cannot know about
119 * held spinlocks in non-preemptible kernels. Thus it should not be
120 * used in the general case to determine whether sleeping is possible.
121 * Do not use in_atomic() in driver code.
122 */
123 #define in_atomic() (preempt_count() != 0)
124
125 /*
126 * Check whether we were atomic before we did preempt_disable():
127 * (used by the scheduler)
128 */
129 #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)
130
131 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
132 extern void preempt_count_add(int val);
133 extern void preempt_count_sub(int val);
134 #define preempt_count_dec_and_test() \
135 ({ preempt_count_sub(1); should_resched(0); })
136 #else
137 #define preempt_count_add(val) __preempt_count_add(val)
138 #define preempt_count_sub(val) __preempt_count_sub(val)
139 #define preempt_count_dec_and_test() __preempt_count_dec_and_test()
140 #endif
141
142 #define __preempt_count_inc() __preempt_count_add(1)
143 #define __preempt_count_dec() __preempt_count_sub(1)
144
145 #define preempt_count_inc() preempt_count_add(1)
146 #define preempt_count_dec() preempt_count_sub(1)
147
148 #ifdef CONFIG_PREEMPT_COUNT
149
150 #define preempt_disable() \
151 do { \
152 preempt_count_inc(); \
153 barrier(); \
154 } while (0)
155
156 #define sched_preempt_enable_no_resched() \
157 do { \
158 barrier(); \
159 preempt_count_dec(); \
160 } while (0)
161
162 #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
163
164 #define preemptible() (preempt_count() == 0 && !irqs_disabled())
165
166 #ifdef CONFIG_PREEMPT
167 #define preempt_enable() \
168 do { \
169 barrier(); \
170 if (unlikely(preempt_count_dec_and_test())) \
171 __preempt_schedule(); \
172 } while (0)
173
174 #define preempt_enable_notrace() \
175 do { \
176 barrier(); \
177 if (unlikely(__preempt_count_dec_and_test())) \
178 __preempt_schedule_notrace(); \
179 } while (0)
180
181 #define preempt_check_resched() \
182 do { \
183 if (should_resched(0)) \
184 __preempt_schedule(); \
185 } while (0)
186
187 #else /* !CONFIG_PREEMPT */
188 #define preempt_enable() \
189 do { \
190 barrier(); \
191 preempt_count_dec(); \
192 } while (0)
193
194 #define preempt_enable_notrace() \
195 do { \
196 barrier(); \
197 __preempt_count_dec(); \
198 } while (0)
199
200 #define preempt_check_resched() do { } while (0)
201 #endif /* CONFIG_PREEMPT */
202
203 #define preempt_disable_notrace() \
204 do { \
205 __preempt_count_inc(); \
206 barrier(); \
207 } while (0)
208
209 #define preempt_enable_no_resched_notrace() \
210 do { \
211 barrier(); \
212 __preempt_count_dec(); \
213 } while (0)
214
215 #else /* !CONFIG_PREEMPT_COUNT */
216
217 /*
218 * Even if we don't have any preemption, we need preempt disable/enable
219 * to be barriers, so that we don't have things like get_user/put_user
220 * that can cause faults and scheduling migrate into our preempt-protected
221 * region.
222 */
223 #define preempt_disable() barrier()
224 #define sched_preempt_enable_no_resched() barrier()
225 #define preempt_enable_no_resched() barrier()
226 #define preempt_enable() barrier()
227 #define preempt_check_resched() do { } while (0)
228
229 #define preempt_disable_notrace() barrier()
230 #define preempt_enable_no_resched_notrace() barrier()
231 #define preempt_enable_notrace() barrier()
232 #define preemptible() 0
233
234 #endif /* CONFIG_PREEMPT_COUNT */
235
236 #ifdef MODULE
237 /*
238 * Modules have no business playing preemption tricks.
239 */
240 #undef sched_preempt_enable_no_resched
241 #undef preempt_enable_no_resched
242 #undef preempt_enable_no_resched_notrace
243 #undef preempt_check_resched
244 #endif
245
246 #define preempt_set_need_resched() \
247 do { \
248 set_preempt_need_resched(); \
249 } while (0)
250 #define preempt_fold_need_resched() \
251 do { \
252 if (tif_need_resched()) \
253 set_preempt_need_resched(); \
254 } while (0)
255
256 #ifdef CONFIG_PREEMPT_NOTIFIERS
257
258 struct preempt_notifier;
259
260 /**
261 * preempt_ops - notifiers called when a task is preempted and rescheduled
262 * @sched_in: we're about to be rescheduled:
263 * notifier: struct preempt_notifier for the task being scheduled
264 * cpu: cpu we're scheduled on
265 * @sched_out: we've just been preempted
266 * notifier: struct preempt_notifier for the task being preempted
267 * next: the task that's kicking us out
268 *
269 * Please note that sched_in and out are called under different
270 * contexts. sched_out is called with rq lock held and irq disabled
271 * while sched_in is called without rq lock and irq enabled. This
272 * difference is intentional and depended upon by its users.
273 */
274 struct preempt_ops {
275 void (*sched_in)(struct preempt_notifier *notifier, int cpu);
276 void (*sched_out)(struct preempt_notifier *notifier,
277 struct task_struct *next);
278 };
279
280 /**
281 * preempt_notifier - key for installing preemption notifiers
282 * @link: internal use
283 * @ops: defines the notifier functions to be called
284 *
285 * Usually used in conjunction with container_of().
286 */
287 struct preempt_notifier {
288 struct hlist_node link;
289 struct preempt_ops *ops;
290 };
291
292 void preempt_notifier_inc(void);
293 void preempt_notifier_dec(void);
294 void preempt_notifier_register(struct preempt_notifier *notifier);
295 void preempt_notifier_unregister(struct preempt_notifier *notifier);
296
preempt_notifier_init(struct preempt_notifier * notifier,struct preempt_ops * ops)297 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
298 struct preempt_ops *ops)
299 {
300 INIT_HLIST_NODE(¬ifier->link);
301 notifier->ops = ops;
302 }
303
304 #endif
305
306 #endif /* __LINUX_PREEMPT_H */
307