LXR linux/include/linux/preempt

   1#ifndef LINUX_PREEMPT_MASK_H
   2#define LINUX_PREEMPT_MASK_H
   3
   4#include <linux/preempt.h>
   5
   6/*
   7 * We put the hardirq and softirq counter into the preemption
   8 * counter. The bitmask has the following meaning:
   9 *
  10 * - bits 0-7 are the preemption count (max preemption depth: 256)
  11 * - bits 8-15 are the softirq count (max # of softirqs: 256)
  12 *
  13 * The hardirq count could in theory be the same as the number of
  14 * interrupts in the system, but we run all interrupt handlers with
  15 * interrupts disabled, so we cannot have nesting interrupts. Though
  16 * there are a few palaeontologic drivers which reenable interrupts in
  17 * the handler, so we need more than one bit here.
  18 *
  19 * PREEMPT_MASK:        0x000000ff
  20 * SOFTIRQ_MASK:        0x0000ff00
  21 * HARDIRQ_MASK:        0x000f0000
  22 *     NMI_MASK:        0x00100000
  23 * PREEMPT_ACTIVE:      0x00200000
  24 */
  25#define PREEMPT_BITS    8
  26#define SOFTIRQ_BITS    8
  27#define HARDIRQ_BITS    4
  28#define NMI_BITS        1
  29
  30#define PREEMPT_SHIFT   0
  31#define SOFTIRQ_SHIFT   (PREEMPT_SHIFT + PREEMPT_BITS)
  32#define HARDIRQ_SHIFT   (SOFTIRQ_SHIFT + SOFTIRQ_BITS)
  33#define NMI_SHIFT       (HARDIRQ_SHIFT + HARDIRQ_BITS)
  34
  35#define __IRQ_MASK(x)   ((1UL << (x))-1)
  36
  37#define PREEMPT_MASK    (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT)
  38#define SOFTIRQ_MASK    (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT)
  39#define HARDIRQ_MASK    (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT)
  40#define NMI_MASK        (__IRQ_MASK(NMI_BITS)     << NMI_SHIFT)
  41
  42#define PREEMPT_OFFSET  (1UL << PREEMPT_SHIFT)
  43#define SOFTIRQ_OFFSET  (1UL << SOFTIRQ_SHIFT)
  44#define HARDIRQ_OFFSET  (1UL << HARDIRQ_SHIFT)
  45#define NMI_OFFSET      (1UL << NMI_SHIFT)
  46
  47#define SOFTIRQ_DISABLE_OFFSET  (2 * SOFTIRQ_OFFSET)
  48
  49#define PREEMPT_ACTIVE_BITS     1
  50#define PREEMPT_ACTIVE_SHIFT    (NMI_SHIFT + NMI_BITS)
  51#define PREEMPT_ACTIVE  (__IRQ_MASK(PREEMPT_ACTIVE_BITS) << PREEMPT_ACTIVE_SHIFT)
  52
  53#define hardirq_count() (preempt_count() & HARDIRQ_MASK)
  54#define softirq_count() (preempt_count() & SOFTIRQ_MASK)
  55#define irq_count()     (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
  56                                 | NMI_MASK))
  57
  58/*
  59 * Are we doing bottom half or hardware interrupt processing?
  60 * Are we in a softirq context? Interrupt context?
  61 * in_softirq - Are we currently processing softirq or have bh disabled?
  62 * in_serving_softirq - Are we currently processing softirq?
  63 */
  64#define in_irq()                (hardirq_count())
  65#define in_softirq()            (softirq_count())
  66#define in_interrupt()          (irq_count())
  67#define in_serving_softirq()    (softirq_count() & SOFTIRQ_OFFSET)
  68
  69/*
  70 * Are we in NMI context?
  71 */
  72#define in_nmi()        (preempt_count() & NMI_MASK)
  73
  74#if defined(CONFIG_PREEMPT_COUNT)
  75# define PREEMPT_CHECK_OFFSET 1
  76#else
  77# define PREEMPT_CHECK_OFFSET 0
  78#endif
  79
  80/*
  81 * The preempt_count offset needed for things like:
  82 *
  83 *  spin_lock_bh()
  84 *
  85 * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and
  86 * softirqs, such that unlock sequences of:
  87 *
  88 *  spin_unlock();
  89 *  local_bh_enable();
  90 *
  91 * Work as expected.
  92 */
  93#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_CHECK_OFFSET)
  94
  95/*
  96 * Are we running in atomic context?  WARNING: this macro cannot
  97 * always detect atomic context; in particular, it cannot know about
  98 * held spinlocks in non-preemptible kernels.  Thus it should not be
  99 * used in the general case to determine whether sleeping is possible.
 100 * Do not use in_atomic() in driver code.
 101 */
 102#define in_atomic()     ((preempt_count() & ~PREEMPT_ACTIVE) != 0)
 103
 104/*
 105 * Check whether we were atomic before we did preempt_disable():
 106 * (used by the scheduler, *after* releasing the kernel lock)
 107 */
 108#define in_atomic_preempt_off() \
 109                ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET)
 110
 111#ifdef CONFIG_PREEMPT_COUNT
 112# define preemptible()  (preempt_count() == 0 && !irqs_disabled())
 113#else
 114# define preemptible()  0
 115#endif
 116
 117#endif /* LINUX_PREEMPT_MASK_H */
 118