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