root/include/linux/hardirq.h

INCLUDED FROM

DEFINITIONS

1. account_system_vtime

#ifndef LINUX_HARDIRQ_H
#define LINUX_HARDIRQ_H

#include <linux/preempt.h>
#include <linux/smp_lock.h>
#include <linux/lockdep.h>
#include <asm/hardirq.h>
#include <asm/system.h>

/*
 * We put the hardirq and softirq counter into the preemption
 * counter. The bitmask has the following meaning:
 *
 * - bits 0-7 are the preemption count (max preemption depth: 256)
 * - bits 8-15 are the softirq count (max # of softirqs: 256)
 *
 * The hardirq count can be overridden per architecture, the default is:
 *
 * - bits 16-27 are the hardirq count (max # of hardirqs: 4096)
 * - ( bit 28 is the PREEMPT_ACTIVE flag. )
 *
 * PREEMPT_MASK: 0x000000ff
 * SOFTIRQ_MASK: 0x0000ff00
 * HARDIRQ_MASK: 0x0fff0000
 */
#define PREEMPT_BITS    8
#define SOFTIRQ_BITS    8

#ifndef HARDIRQ_BITS
#define HARDIRQ_BITS    12

#ifndef MAX_HARDIRQS_PER_CPU
#define MAX_HARDIRQS_PER_CPU NR_IRQS
#endif

/*
 * The hardirq mask has to be large enough to have space for potentially
 * all IRQ sources in the system nesting on a single CPU.
 */
#if (1 << HARDIRQ_BITS) < MAX_HARDIRQS_PER_CPU
# error HARDIRQ_BITS is too low!
#endif
#endif

#define PREEMPT_SHIFT   0
#define SOFTIRQ_SHIFT   (PREEMPT_SHIFT + PREEMPT_BITS)
#define HARDIRQ_SHIFT   (SOFTIRQ_SHIFT + SOFTIRQ_BITS)

#define __IRQ_MASK(x)   ((1UL << (x))-1)

#define PREEMPT_MASK    (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT)
#define SOFTIRQ_MASK    (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT)
#define HARDIRQ_MASK    (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT)

#define PREEMPT_OFFSET  (1UL << PREEMPT_SHIFT)
#define SOFTIRQ_OFFSET  (1UL << SOFTIRQ_SHIFT)
#define HARDIRQ_OFFSET  (1UL << HARDIRQ_SHIFT)

#if PREEMPT_ACTIVE < (1 << (HARDIRQ_SHIFT + HARDIRQ_BITS))
#error PREEMPT_ACTIVE is too low!
#endif

#define hardirq_count() (preempt_count() & HARDIRQ_MASK)
#define softirq_count() (preempt_count() & SOFTIRQ_MASK)
#define irq_count()     (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK))

/*
 * Are we doing bottom half or hardware interrupt processing?
 * Are we in a softirq context? Interrupt context?
 */
#define in_irq()                (hardirq_count())
#define in_softirq()            (softirq_count())
#define in_interrupt()          (irq_count())

#if defined(CONFIG_PREEMPT)
# define PREEMPT_INATOMIC_BASE kernel_locked()
# define PREEMPT_CHECK_OFFSET 1
#else
# define PREEMPT_INATOMIC_BASE 0
# define PREEMPT_CHECK_OFFSET 0
#endif

/*
 * Are we running in atomic context?  WARNING: this macro cannot
 * always detect atomic context; in particular, it cannot know about
 * held spinlocks in non-preemptible kernels.  Thus it should not be
 * used in the general case to determine whether sleeping is possible.
 * Do not use in_atomic() in driver code.
 */
#define in_atomic()     ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_INATOMIC_BASE)

/*
 * Check whether we were atomic before we did preempt_disable():
 * (used by the scheduler, *after* releasing the kernel lock)
 */
#define in_atomic_preempt_off() \
                ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET)

#ifdef CONFIG_PREEMPT
# define preemptible()  (preempt_count() == 0 && !irqs_disabled())
# define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
#else
# define preemptible()  0
# define IRQ_EXIT_OFFSET HARDIRQ_OFFSET
#endif

#ifdef CONFIG_SMP
extern void synchronize_irq(unsigned int irq);
#else
# define synchronize_irq(irq)   barrier()
#endif

struct task_struct;

#ifndef CONFIG_VIRT_CPU_ACCOUNTING
static inline void account_system_vtime(struct task_struct *tsk)
{
}
#endif

#if defined(CONFIG_PREEMPT_RCU) && defined(CONFIG_NO_HZ)
extern void rcu_irq_enter(void);
extern void rcu_irq_exit(void);
#else
# define rcu_irq_enter() do { } while (0)
# define rcu_irq_exit() do { } while (0)
#endif /* CONFIG_PREEMPT_RCU */

/*
 * It is safe to do non-atomic ops on ->hardirq_context,
 * because NMI handlers may not preempt and the ops are
 * always balanced, so the interrupted value of ->hardirq_context
 * will always be restored.
 */
#define __irq_enter()                                   \
        do {                                            \
                rcu_irq_enter();                        \
                account_system_vtime(current);          \
                add_preempt_count(HARDIRQ_OFFSET);      \
                trace_hardirq_enter();                  \
        } while (0)

/*
 * Enter irq context (on NO_HZ, update jiffies):
 */
extern void irq_enter(void);

/*
 * Exit irq context without processing softirqs:
 */
#define __irq_exit()                                    \
        do {                                            \
                trace_hardirq_exit();                   \
                account_system_vtime(current);          \
                sub_preempt_count(HARDIRQ_OFFSET);      \
                rcu_irq_exit();                         \
        } while (0)

/*
 * Exit irq context and process softirqs if needed:
 */
extern void irq_exit(void);

#define nmi_enter()             do { lockdep_off(); __irq_enter(); } while (0)
#define nmi_exit()              do { __irq_exit(); lockdep_on(); } while (0)

#endif /* LINUX_HARDIRQ_H */