1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef __LINUX_PREEMPT_H |
3 | #define __LINUX_PREEMPT_H |
4 | |
5 | /* |
6 | * include/linux/preempt.h - macros for accessing and manipulating |
7 | * preempt_count (used for kernel preemption, interrupt count, etc.) |
8 | */ |
9 | |
10 | #include <linux/linkage.h> |
11 | #include <linux/list.h> |
12 | |
13 | /* |
14 | * We put the hardirq and softirq counter into the preemption |
15 | * counter. The bitmask has the following meaning: |
16 | * |
17 | * - bits 0-7 are the preemption count (max preemption depth: 256) |
18 | * - bits 8-15 are the softirq count (max # of softirqs: 256) |
19 | * |
20 | * The hardirq count could in theory be the same as the number of |
21 | * interrupts in the system, but we run all interrupt handlers with |
22 | * interrupts disabled, so we cannot have nesting interrupts. Though |
23 | * there are a few palaeontologic drivers which reenable interrupts in |
24 | * the handler, so we need more than one bit here. |
25 | * |
26 | * PREEMPT_MASK: 0x000000ff |
27 | * SOFTIRQ_MASK: 0x0000ff00 |
28 | * HARDIRQ_MASK: 0x000f0000 |
29 | * NMI_MASK: 0x00100000 |
30 | * PREEMPT_NEED_RESCHED: 0x80000000 |
31 | */ |
32 | #define PREEMPT_BITS 8 |
33 | #define SOFTIRQ_BITS 8 |
34 | #define HARDIRQ_BITS 4 |
35 | #define NMI_BITS 1 |
36 | |
37 | #define PREEMPT_SHIFT 0 |
38 | #define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) |
39 | #define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) |
40 | #define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) |
41 | |
42 | #define __IRQ_MASK(x) ((1UL << (x))-1) |
43 | |
44 | #define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT) |
45 | #define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) |
46 | #define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) |
47 | #define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) |
48 | |
49 | #define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT) |
50 | #define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) |
51 | #define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT) |
52 | #define NMI_OFFSET (1UL << NMI_SHIFT) |
53 | |
54 | #define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET) |
55 | |
56 | #define PREEMPT_DISABLED (PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) |
57 | |
58 | /* |
59 | * Disable preemption until the scheduler is running -- use an unconditional |
60 | * value so that it also works on !PREEMPT_COUNT kernels. |
61 | * |
62 | * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count(). |
63 | */ |
64 | #define INIT_PREEMPT_COUNT PREEMPT_OFFSET |
65 | |
66 | /* |
67 | * Initial preempt_count value; reflects the preempt_count schedule invariant |
68 | * which states that during context switches: |
69 | * |
70 | * preempt_count() == 2*PREEMPT_DISABLE_OFFSET |
71 | * |
72 | * Note: PREEMPT_DISABLE_OFFSET is 0 for !PREEMPT_COUNT kernels. |
73 | * Note: See finish_task_switch(). |
74 | */ |
75 | #define FORK_PREEMPT_COUNT (2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) |
76 | |
77 | /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ |
78 | #include <asm/preempt.h> |
79 | |
80 | #define hardirq_count() (preempt_count() & HARDIRQ_MASK) |
81 | #define softirq_count() (preempt_count() & SOFTIRQ_MASK) |
82 | #define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ |
83 | | NMI_MASK)) |
84 | |
85 | /* |
86 | * Are we doing bottom half or hardware interrupt processing? |
87 | * |
88 | * in_irq() - We're in (hard) IRQ context |
89 | * in_softirq() - We have BH disabled, or are processing softirqs |
90 | * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled |
91 | * in_serving_softirq() - We're in softirq context |
92 | * in_nmi() - We're in NMI context |
93 | * in_task() - We're in task context |
94 | * |
95 | * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really |
96 | * should not be used in new code. |
97 | */ |
98 | #define in_irq() (hardirq_count()) |
99 | #define in_softirq() (softirq_count()) |
100 | #define in_interrupt() (irq_count()) |
101 | #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) |
102 | #define in_nmi() (preempt_count() & NMI_MASK) |
103 | #define in_task() (!(preempt_count() & \ |
104 | (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) |
105 | |
106 | /* |
107 | * The preempt_count offset after preempt_disable(); |
108 | */ |
109 | #if defined(CONFIG_PREEMPT_COUNT) |
110 | # define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET |
111 | #else |
112 | # define PREEMPT_DISABLE_OFFSET 0 |
113 | #endif |
114 | |
115 | /* |
116 | * The preempt_count offset after spin_lock() |
117 | */ |
118 | #define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET |
119 | |
120 | /* |
121 | * The preempt_count offset needed for things like: |
122 | * |
123 | * spin_lock_bh() |
124 | * |
125 | * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and |
126 | * softirqs, such that unlock sequences of: |
127 | * |
128 | * spin_unlock(); |
129 | * local_bh_enable(); |
130 | * |
131 | * Work as expected. |
132 | */ |
133 | #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET) |
134 | |
135 | /* |
136 | * Are we running in atomic context? WARNING: this macro cannot |
137 | * always detect atomic context; in particular, it cannot know about |
138 | * held spinlocks in non-preemptible kernels. Thus it should not be |
139 | * used in the general case to determine whether sleeping is possible. |
140 | * Do not use in_atomic() in driver code. |
141 | */ |
142 | #define in_atomic() (preempt_count() != 0) |
143 | |
144 | /* |
145 | * Check whether we were atomic before we did preempt_disable(): |
146 | * (used by the scheduler) |
147 | */ |
148 | #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET) |
149 | |
150 | #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE) |
151 | extern void preempt_count_add(int val); |
152 | extern void preempt_count_sub(int val); |
153 | #define preempt_count_dec_and_test() \ |
154 | ({ preempt_count_sub(1); should_resched(0); }) |
155 | #else |
156 | #define preempt_count_add(val) __preempt_count_add(val) |
157 | #define preempt_count_sub(val) __preempt_count_sub(val) |
158 | #define preempt_count_dec_and_test() __preempt_count_dec_and_test() |
159 | #endif |
160 | |
161 | #define __preempt_count_inc() __preempt_count_add(1) |
162 | #define __preempt_count_dec() __preempt_count_sub(1) |
163 | |
164 | #define preempt_count_inc() preempt_count_add(1) |
165 | #define preempt_count_dec() preempt_count_sub(1) |
166 | |
167 | #ifdef CONFIG_PREEMPT_COUNT |
168 | |
169 | #define preempt_disable() \ |
170 | do { \ |
171 | preempt_count_inc(); \ |
172 | barrier(); \ |
173 | } while (0) |
174 | |
175 | #define sched_preempt_enable_no_resched() \ |
176 | do { \ |
177 | barrier(); \ |
178 | preempt_count_dec(); \ |
179 | } while (0) |
180 | |
181 | #define preempt_enable_no_resched() sched_preempt_enable_no_resched() |
182 | |
183 | #define preemptible() (preempt_count() == 0 && !irqs_disabled()) |
184 | |
185 | #ifdef CONFIG_PREEMPT |
186 | #define preempt_enable() \ |
187 | do { \ |
188 | barrier(); \ |
189 | if (unlikely(preempt_count_dec_and_test())) \ |
190 | __preempt_schedule(); \ |
191 | } while (0) |
192 | |
193 | #define preempt_enable_notrace() \ |
194 | do { \ |
195 | barrier(); \ |
196 | if (unlikely(__preempt_count_dec_and_test())) \ |
197 | __preempt_schedule_notrace(); \ |
198 | } while (0) |
199 | |
200 | #define preempt_check_resched() \ |
201 | do { \ |
202 | if (should_resched(0)) \ |
203 | __preempt_schedule(); \ |
204 | } while (0) |
205 | |
206 | #else /* !CONFIG_PREEMPT */ |
207 | #define preempt_enable() \ |
208 | do { \ |
209 | barrier(); \ |
210 | preempt_count_dec(); \ |
211 | } while (0) |
212 | |
213 | #define preempt_enable_notrace() \ |
214 | do { \ |
215 | barrier(); \ |
216 | __preempt_count_dec(); \ |
217 | } while (0) |
218 | |
219 | #define preempt_check_resched() do { } while (0) |
220 | #endif /* CONFIG_PREEMPT */ |
221 | |
222 | #define preempt_disable_notrace() \ |
223 | do { \ |
224 | __preempt_count_inc(); \ |
225 | barrier(); \ |
226 | } while (0) |
227 | |
228 | #define preempt_enable_no_resched_notrace() \ |
229 | do { \ |
230 | barrier(); \ |
231 | __preempt_count_dec(); \ |
232 | } while (0) |
233 | |
234 | #else /* !CONFIG_PREEMPT_COUNT */ |
235 | |
236 | /* |
237 | * Even if we don't have any preemption, we need preempt disable/enable |
238 | * to be barriers, so that we don't have things like get_user/put_user |
239 | * that can cause faults and scheduling migrate into our preempt-protected |
240 | * region. |
241 | */ |
242 | #define preempt_disable() barrier() |
243 | #define sched_preempt_enable_no_resched() barrier() |
244 | #define preempt_enable_no_resched() barrier() |
245 | #define preempt_enable() barrier() |
246 | #define preempt_check_resched() do { } while (0) |
247 | |
248 | #define preempt_disable_notrace() barrier() |
249 | #define preempt_enable_no_resched_notrace() barrier() |
250 | #define preempt_enable_notrace() barrier() |
251 | #define preemptible() 0 |
252 | |
253 | #endif /* CONFIG_PREEMPT_COUNT */ |
254 | |
255 | #ifdef MODULE |
256 | /* |
257 | * Modules have no business playing preemption tricks. |
258 | */ |
259 | #undef sched_preempt_enable_no_resched |
260 | #undef preempt_enable_no_resched |
261 | #undef preempt_enable_no_resched_notrace |
262 | #undef preempt_check_resched |
263 | #endif |
264 | |
265 | #define preempt_set_need_resched() \ |
266 | do { \ |
267 | set_preempt_need_resched(); \ |
268 | } while (0) |
269 | #define preempt_fold_need_resched() \ |
270 | do { \ |
271 | if (tif_need_resched()) \ |
272 | set_preempt_need_resched(); \ |
273 | } while (0) |
274 | |
275 | #ifdef CONFIG_PREEMPT_NOTIFIERS |
276 | |
277 | struct preempt_notifier; |
278 | |
279 | /** |
280 | * preempt_ops - notifiers called when a task is preempted and rescheduled |
281 | * @sched_in: we're about to be rescheduled: |
282 | * notifier: struct preempt_notifier for the task being scheduled |
283 | * cpu: cpu we're scheduled on |
284 | * @sched_out: we've just been preempted |
285 | * notifier: struct preempt_notifier for the task being preempted |
286 | * next: the task that's kicking us out |
287 | * |
288 | * Please note that sched_in and out are called under different |
289 | * contexts. sched_out is called with rq lock held and irq disabled |
290 | * while sched_in is called without rq lock and irq enabled. This |
291 | * difference is intentional and depended upon by its users. |
292 | */ |
293 | struct preempt_ops { |
294 | void (*sched_in)(struct preempt_notifier *notifier, int cpu); |
295 | void (*sched_out)(struct preempt_notifier *notifier, |
296 | struct task_struct *next); |
297 | }; |
298 | |
299 | /** |
300 | * preempt_notifier - key for installing preemption notifiers |
301 | * @link: internal use |
302 | * @ops: defines the notifier functions to be called |
303 | * |
304 | * Usually used in conjunction with container_of(). |
305 | */ |
306 | struct preempt_notifier { |
307 | struct hlist_node link; |
308 | struct preempt_ops *ops; |
309 | }; |
310 | |
311 | void preempt_notifier_inc(void); |
312 | void preempt_notifier_dec(void); |
313 | void preempt_notifier_register(struct preempt_notifier *notifier); |
314 | void preempt_notifier_unregister(struct preempt_notifier *notifier); |
315 | |
316 | static inline void preempt_notifier_init(struct preempt_notifier *notifier, |
317 | struct preempt_ops *ops) |
318 | { |
319 | INIT_HLIST_NODE(¬ifier->link); |
320 | notifier->ops = ops; |
321 | } |
322 | |
323 | #endif |
324 | |
325 | #endif /* __LINUX_PREEMPT_H */ |
326 | |