include/linux/preempt.h

   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_ACTIVE:        0x00200000
  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_ACTIVE_BITS     1
  57 #define PREEMPT_ACTIVE_SHIFT    (NMI_SHIFT + NMI_BITS)
  58 #define PREEMPT_ACTIVE  (__IRQ_MASK(PREEMPT_ACTIVE_BITS) << PREEMPT_ACTIVE_SHIFT)
  59
  60 /* We use the MSB mostly because its available */
  61 #define PREEMPT_NEED_RESCHED    0x80000000
  62
  63 /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */
  64 #include <asm/preempt.h>
  65
  66 #define hardirq_count() (preempt_count() & HARDIRQ_MASK)
  67 #define softirq_count() (preempt_count() & SOFTIRQ_MASK)
  68 #define irq_count()     (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
  69                                  | NMI_MASK))
  70
  71 /*
  72  * Are we doing bottom half or hardware interrupt processing?
  73  * Are we in a softirq context? Interrupt context?
  74  * in_softirq - Are we currently processing softirq or have bh disabled?
  75  * in_serving_softirq - Are we currently processing softirq?
  76  */
  77 #define in_irq()                (hardirq_count())
  78 #define in_softirq()            (softirq_count())
  79 #define in_interrupt()          (irq_count())
  80 #define in_serving_softirq()    (softirq_count() & SOFTIRQ_OFFSET)
  81
  82 /*
  83  * Are we in NMI context?
  84  */
  85 #define in_nmi()        (preempt_count() & NMI_MASK)
  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() \
 130                 ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_DISABLE_OFFSET)
 131
 132 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
 133 extern void preempt_count_add(int val);
 134 extern void preempt_count_sub(int val);
 135 #define preempt_count_dec_and_test() \
 136         ({ preempt_count_sub(1); should_resched(0); })
 137 #else
 138 #define preempt_count_add(val)  __preempt_count_add(val)
 139 #define preempt_count_sub(val)  __preempt_count_sub(val)
 140 #define preempt_count_dec_and_test() __preempt_count_dec_and_test()
 141 #endif
 142
 143 #define __preempt_count_inc() __preempt_count_add(1)
 144 #define __preempt_count_dec() __preempt_count_sub(1)
 145
 146 #define preempt_count_inc() preempt_count_add(1)
 147 #define preempt_count_dec() preempt_count_sub(1)
 148
 149 #define preempt_active_enter() \
 150 do { \
 151         preempt_count_add(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET); \
 152         barrier(); \
 153 } while (0)
 154
 155 #define preempt_active_exit() \
 156 do { \
 157         barrier(); \
 158         preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET); \
 159 } while (0)
 160
 161 #ifdef CONFIG_PREEMPT_COUNT
 162
 163 #define preempt_disable() \
 164 do { \
 165         preempt_count_inc(); \
 166         barrier(); \
 167 } while (0)
 168
 169 #define sched_preempt_enable_no_resched() \
 170 do { \
 171         barrier(); \
 172         preempt_count_dec(); \
 173 } while (0)
 174
 175 #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
 176
 177 #define preemptible()   (preempt_count() == 0 && !irqs_disabled())
 178
 179 #ifdef CONFIG_PREEMPT
 180 #define preempt_enable() \
 181 do { \
 182         barrier(); \
 183         if (unlikely(preempt_count_dec_and_test())) \
 184                 __preempt_schedule(); \
 185 } while (0)
 186
 187 #define preempt_enable_notrace() \
 188 do { \
 189         barrier(); \
 190         if (unlikely(__preempt_count_dec_and_test())) \
 191                 __preempt_schedule_notrace(); \
 192 } while (0)
 193
 194 #define preempt_check_resched() \
 195 do { \
 196         if (should_resched(0)) \
 197                 __preempt_schedule(); \
 198 } while (0)
 199
 200 #else /* !CONFIG_PREEMPT */
 201 #define preempt_enable() \
 202 do { \
 203         barrier(); \
 204         preempt_count_dec(); \
 205 } while (0)
 206
 207 #define preempt_enable_notrace() \
 208 do { \
 209         barrier(); \
 210         __preempt_count_dec(); \
 211 } while (0)
 212
 213 #define preempt_check_resched() do { } while (0)
 214 #endif /* CONFIG_PREEMPT */
 215
 216 #define preempt_disable_notrace() \
 217 do { \
 218         __preempt_count_inc(); \
 219         barrier(); \
 220 } while (0)
 221
 222 #define preempt_enable_no_resched_notrace() \
 223 do { \
 224         barrier(); \
 225         __preempt_count_dec(); \
 226 } while (0)
 227
 228 #else /* !CONFIG_PREEMPT_COUNT */
 229
 230 /*
 231  * Even if we don't have any preemption, we need preempt disable/enable
 232  * to be barriers, so that we don't have things like get_user/put_user
 233  * that can cause faults and scheduling migrate into our preempt-protected
 234  * region.
 235  */
 236 #define preempt_disable()                       barrier()
 237 #define sched_preempt_enable_no_resched()       barrier()
 238 #define preempt_enable_no_resched()             barrier()
 239 #define preempt_enable()                        barrier()
 240 #define preempt_check_resched()                 do { } while (0)
 241
 242 #define preempt_disable_notrace()               barrier()
 243 #define preempt_enable_no_resched_notrace()     barrier()
 244 #define preempt_enable_notrace()                barrier()
 245 #define preemptible()                           0
 246
 247 #endif /* CONFIG_PREEMPT_COUNT */
 248
 249 #ifdef MODULE
 250 /*
 251  * Modules have no business playing preemption tricks.
 252  */
 253 #undef sched_preempt_enable_no_resched
 254 #undef preempt_enable_no_resched
 255 #undef preempt_enable_no_resched_notrace
 256 #undef preempt_check_resched
 257 #endif
 258
 259 #define preempt_set_need_resched() \
 260 do { \
 261         set_preempt_need_resched(); \
 262 } while (0)
 263 #define preempt_fold_need_resched() \
 264 do { \
 265         if (tif_need_resched()) \
 266                 set_preempt_need_resched(); \
 267 } while (0)
 268
 269 #ifdef CONFIG_PREEMPT_NOTIFIERS
 270
 271 struct preempt_notifier;
 272
 273 /**
 274  * preempt_ops - notifiers called when a task is preempted and rescheduled
 275  * @sched_in: we're about to be rescheduled:
 276  *    notifier: struct preempt_notifier for the task being scheduled
 277  *    cpu:  cpu we're scheduled on
 278  * @sched_out: we've just been preempted
 279  *    notifier: struct preempt_notifier for the task being preempted
 280  *    next: the task that's kicking us out
 281  *
 282  * Please note that sched_in and out are called under different
 283  * contexts.  sched_out is called with rq lock held and irq disabled
 284  * while sched_in is called without rq lock and irq enabled.  This
 285  * difference is intentional and depended upon by its users.
 286  */
 287 struct preempt_ops {
 288         void (*sched_in)(struct preempt_notifier *notifier, int cpu);
 289         void (*sched_out)(struct preempt_notifier *notifier,
 290                           struct task_struct *next);
 291 };
 292
 293 /**
 294  * preempt_notifier - key for installing preemption notifiers
 295  * @link: internal use
 296  * @ops: defines the notifier functions to be called
 297  *
 298  * Usually used in conjunction with container_of().
 299  */
 300 struct preempt_notifier {
 301         struct hlist_node link;
 302         struct preempt_ops *ops;
 303 };
 304
 305 void preempt_notifier_inc(void);
 306 void preempt_notifier_dec(void);
 307 void preempt_notifier_register(struct preempt_notifier *notifier);
 308 void preempt_notifier_unregister(struct preempt_notifier *notifier);
 309
 310 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
 311                                      struct preempt_ops *ops)
 312 {
 313         INIT_HLIST_NODE(&notifier->link);
 314         notifier->ops = ops;
 315 }
 316
 317 #endif
 318
 319 #endif /* __LINUX_PREEMPT_H */