projects/linux·blob v4.12 · refs

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