Quelle  spinlock.h   Sprache: C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_SPINLOCK_H
#define __LINUX_SPINLOCK_H
#define __LINUX_INSIDE_SPINLOCK_H

/*
 * include/linux/spinlock.h - generic spinlock/rwlock declarations
 *
 * here's the role of the various spinlock/rwlock related include files:
 *
 * on SMP builds:
 *
 *  asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the
 *                        initializers
 *
 *  linux/spinlock_types_raw:
 *   The raw types and initializers
 *  linux/spinlock_types.h:
 *                        defines the generic type and initializers
 *
 *  asm/spinlock.h:       contains the arch_spin_*()/etc. lowlevel
 *                        implementations, mostly inline assembly code
 *
 *   (also included on UP-debug builds:)
 *
 *  linux/spinlock_api_smp.h:
 *                        contains the prototypes for the _spin_*() APIs.
 *
 *  linux/spinlock.h:     builds the final spin_*() APIs.
 *
 * on UP builds:
 *
 *  linux/spinlock_type_up.h:
 *                        contains the generic, simplified UP spinlock type.
 *                        (which is an empty structure on non-debug builds)
 *
 *  linux/spinlock_types_raw:
 *   The raw RT types and initializers
 *  linux/spinlock_types.h:
 *                        defines the generic type and initializers
 *
 *  linux/spinlock_up.h:
 *                        contains the arch_spin_*()/etc. version of UP
 *                        builds. (which are NOPs on non-debug, non-preempt
 *                        builds)
 *
 *   (included on UP-non-debug builds:)
 *
 *  linux/spinlock_api_up.h:
 *                        builds the _spin_*() APIs.
 *
 *  linux/spinlock.h:     builds the final spin_*() APIs.
 */

#include <linux/typecheck.h>
#include <linux/preempt.h>
#include <linux/linkage.h>
#include <linux/compiler.h>
#include <linux/irqflags.h>
#include <linux/thread_info.h>
#include <linux/stringify.h>
#include <linux/bottom_half.h>
#include <linux/lockdep.h>
#include <linux/cleanup.h>
#include <asm/barrier.h>
#include <asm/mmiowb.h>


/*
 * Must define these before including other files, inline functions need them
 */
#define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME

#define LOCK_SECTION_START(extra)               \
        ".subsection 1\n\t"                     \
        extra                                   \
        ".ifndef " LOCK_SECTION_NAME "\n\t"     \
        LOCK_SECTION_NAME ":\n\t"               \
        ".endif\n"

#define LOCK_SECTION_END                        \
        ".previous\n\t"

#define __lockfunc __section(".spinlock.text")

/*
 * Pull the arch_spinlock_t and arch_rwlock_t definitions:
 */
#include <linux/spinlock_types.h>

/*
 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
 */
#ifdef CONFIG_SMP
# include <asm/spinlock.h>
#else
# include <linux/spinlock_up.h>
#endif

#ifdef CONFIG_DEBUG_SPINLOCK
  extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
       struct lock_class_key *key, short inner);

# define raw_spin_lock_init(lock)     \
do {         \
 static struct lock_class_key __key;    \
         \
 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \
} while (0)

#else
# define raw_spin_lock_init(lock)    \
 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
#endif

#define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)

#ifdef arch_spin_is_contended
#define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
#else
#define raw_spin_is_contended(lock) (((void)(lock), 0))
#endif /*arch_spin_is_contended*/

/*
 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
 * between program-order earlier lock acquisitions and program-order later
 * memory accesses.
 *
 * This guarantees that the following two properties hold:
 *
 *   1) Given the snippet:
 *
 *   { X = 0;  Y = 0; }
 *
 *   CPU0 CPU1
 *
 *   WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
 *   spin_lock(S); smp_mb();
 *   smp_mb__after_spinlock(); r1 = READ_ONCE(X);
 *   r0 = READ_ONCE(Y);
 *   spin_unlock(S);
 *
 *      it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
 *      and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
 *      preceding the call to smp_mb__after_spinlock() in __schedule() and in
 *      try_to_wake_up().
 *
 *   2) Given the snippet:
 *
 *  { X = 0;  Y = 0; }
 *
 *  CPU0 CPU1 CPU2
 *
 *  spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y);
 *  WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb();
 *  spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X);
 * WRITE_ONCE(Y, 1);
 * spin_unlock(S);
 *
 *      it is forbidden that CPU0's critical section executes before CPU1's
 *      critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
 *      and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
 *      preceding the calls to smp_rmb() in try_to_wake_up() for similar
 *      snippets but "projected" onto two CPUs.
 *
 * Property (2) upgrades the lock to an RCsc lock.
 *
 * Since most load-store architectures implement ACQUIRE with an smp_mb() after
 * the LL/SC loop, they need no further barriers. Similarly all our TSO
 * architectures imply an smp_mb() for each atomic instruction and equally don't
 * need more.
 *
 * Architectures that can implement ACQUIRE better need to take care.
 */
#ifndef smp_mb__after_spinlock
#define smp_mb__after_spinlock() kcsan_mb()
#endif

#ifdef CONFIG_DEBUG_SPINLOCK
 extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 extern int do_raw_spin_trylock(raw_spinlock_t *lock);
 extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
#else
static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
{
 __acquire(lock);
 arch_spin_lock(&lock->raw_lock);
 mmiowb_spin_lock();
}

static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
{
 int ret = arch_spin_trylock(&(lock)->raw_lock);

 if (ret)
  mmiowb_spin_lock();

 return ret;
}

static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
{
 mmiowb_spin_unlock();
 arch_spin_unlock(&lock->raw_lock);
 __release(lock);
}
#endif

/*
 * Define the various spin_lock methods.  Note we define these
 * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
 * various methods are defined as nops in the case they are not
 * required.
 */
#define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))

#define raw_spin_lock(lock) _raw_spin_lock(lock)

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define raw_spin_lock_nested(lock, subclass) \
 _raw_spin_lock_nested(lock, subclass)

# define raw_spin_lock_nest_lock(lock, nest_lock)   \
  do {        \
   typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
   _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
  } while (0)
#else
/*
 * Always evaluate the 'subclass' argument to avoid that the compiler
 * warns about set-but-not-used variables when building with
 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 */
# define raw_spin_lock_nested(lock, subclass)  \
 _raw_spin_lock(((void)(subclass), (lock)))
# define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
#endif

#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)

#define raw_spin_lock_irqsave(lock, flags)   \
 do {      \
  typecheck(unsigned long, flags); \
  flags = _raw_spin_lock_irqsave(lock); \
 } while (0)

#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define raw_spin_lock_irqsave_nested(lock, flags, subclass)  \
 do {        \
  typecheck(unsigned long, flags);   \
  flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
 } while (0)
#else
#define raw_spin_lock_irqsave_nested(lock, flags, subclass)  \
 do {        \
  typecheck(unsigned long, flags);   \
  flags = _raw_spin_lock_irqsave(lock);   \
 } while (0)
#endif

#else

#define raw_spin_lock_irqsave(lock, flags)  \
 do {      \
  typecheck(unsigned long, flags); \
  _raw_spin_lock_irqsave(lock, flags); \
 } while (0)

#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
 raw_spin_lock_irqsave(lock, flags)

#endif

#define raw_spin_lock_irq(lock)  _raw_spin_lock_irq(lock)
#define raw_spin_lock_bh(lock)  _raw_spin_lock_bh(lock)
#define raw_spin_unlock(lock)  _raw_spin_unlock(lock)
#define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)

#define raw_spin_unlock_irqrestore(lock, flags)  \
 do {       \
  typecheck(unsigned long, flags);  \
  _raw_spin_unlock_irqrestore(lock, flags); \
 } while (0)
#define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)

#define raw_spin_trylock_bh(lock) \
 __cond_lock(lock, _raw_spin_trylock_bh(lock))

#define raw_spin_trylock_irq(lock) \
({ \
 local_irq_disable(); \
 raw_spin_trylock(lock) ? \
 1 : ({ local_irq_enable(); 0;  }); \
})

#define raw_spin_trylock_irqsave(lock, flags) \
({ \
 local_irq_save(flags); \
 raw_spin_trylock(lock) ? \
 1 : ({ local_irq_restore(flags); 0; }); \
})

#ifndef CONFIG_PREEMPT_RT
/* Include rwlock functions for !RT */
#include <linux/rwlock.h>
#endif

/*
 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 */
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
# include <linux/spinlock_api_smp.h>
#else
# include <linux/spinlock_api_up.h>
#endif

/* Non PREEMPT_RT kernel, map to raw spinlocks: */
#ifndef CONFIG_PREEMPT_RT

/*
 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 */

static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
{
 return &lock->rlock;
}

#ifdef CONFIG_DEBUG_SPINLOCK

# define spin_lock_init(lock)     \
do {        \
 static struct lock_class_key __key;   \
        \
 __raw_spin_lock_init(spinlock_check(lock),  \
        #lock, &__key, LD_WAIT_CONFIG); \
} while (0)

#else

# define spin_lock_init(_lock)   \
do {      \
 spinlock_check(_lock);   \
 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
} while (0)

#endif

static __always_inline void spin_lock(spinlock_t *lock)
{
 raw_spin_lock(&lock->rlock);
}

static __always_inline void spin_lock_bh(spinlock_t *lock)
{
 raw_spin_lock_bh(&lock->rlock);
}

static __always_inline int spin_trylock(spinlock_t *lock)
{
 return raw_spin_trylock(&lock->rlock);
}

#define spin_lock_nested(lock, subclass)   \
do {        \
 raw_spin_lock_nested(spinlock_check(lock), subclass); \
} while (0)

#define spin_lock_nest_lock(lock, nest_lock)    \
do {         \
 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
} while (0)

static __always_inline void spin_lock_irq(spinlock_t *lock)
{
 raw_spin_lock_irq(&lock->rlock);
}

#define spin_lock_irqsave(lock, flags)    \
do {        \
 raw_spin_lock_irqsave(spinlock_check(lock), flags); \
} while (0)

#define spin_lock_irqsave_nested(lock, flags, subclass)   \
do {         \
 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
} while (0)

static __always_inline void spin_unlock(spinlock_t *lock)
{
 raw_spin_unlock(&lock->rlock);
}

static __always_inline void spin_unlock_bh(spinlock_t *lock)
{
 raw_spin_unlock_bh(&lock->rlock);
}

static __always_inline void spin_unlock_irq(spinlock_t *lock)
{
 raw_spin_unlock_irq(&lock->rlock);
}

static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
{
 raw_spin_unlock_irqrestore(&lock->rlock, flags);
}

static __always_inline int spin_trylock_bh(spinlock_t *lock)
{
 return raw_spin_trylock_bh(&lock->rlock);
}

static __always_inline int spin_trylock_irq(spinlock_t *lock)
{
 return raw_spin_trylock_irq(&lock->rlock);
}

#define spin_trylock_irqsave(lock, flags)   \
({        \
 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
})

/**
 * spin_is_locked() - Check whether a spinlock is locked.
 * @lock: Pointer to the spinlock.
 *
 * This function is NOT required to provide any memory ordering
 * guarantees; it could be used for debugging purposes or, when
 * additional synchronization is needed, accompanied with other
 * constructs (memory barriers) enforcing the synchronization.
 *
 * Returns: 1 if @lock is locked, 0 otherwise.
 *
 * Note that the function only tells you that the spinlock is
 * seen to be locked, not that it is locked on your CPU.
 *
 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
 * the return value is always 0 (see include/linux/spinlock_up.h).
 * Therefore you should not rely heavily on the return value.
 */
static __always_inline int spin_is_locked(spinlock_t *lock)
{
 return raw_spin_is_locked(&lock->rlock);
}

static __always_inline int spin_is_contended(spinlock_t *lock)
{
 return raw_spin_is_contended(&lock->rlock);
}

#define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)

#else  /* !CONFIG_PREEMPT_RT */
# include <linux/spinlock_rt.h>
#endif /* CONFIG_PREEMPT_RT */

/*
 * Does a critical section need to be broken due to another
 * task waiting?: (technically does not depend on CONFIG_PREEMPTION,
 * but a general need for low latency)
 */
static inline int spin_needbreak(spinlock_t *lock)
{
 if (!preempt_model_preemptible())
  return 0;

 return spin_is_contended(lock);
}

/*
 * Check if a rwlock is contended.
 * Returns non-zero if there is another task waiting on the rwlock.
 * Returns zero if the lock is not contended or the system / underlying
 * rwlock implementation does not support contention detection.
 * Technically does not depend on CONFIG_PREEMPTION, but a general need
 * for low latency.
 */
static inline int rwlock_needbreak(rwlock_t *lock)
{
 if (!preempt_model_preemptible())
  return 0;

 return rwlock_is_contended(lock);
}

/*
 * Pull the atomic_t declaration:
 * (asm-mips/atomic.h needs above definitions)
 */
#include <linux/atomic.h>
/**
 * atomic_dec_and_lock - lock on reaching reference count zero
 * @atomic: the atomic counter
 * @lock: the spinlock in question
 *
 * Decrements @atomic by 1.  If the result is 0, returns true and locks
 * @lock.  Returns false for all other cases.
 */
extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
#define atomic_dec_and_lock(atomic, lock) \
  __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))

extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
     unsigned long *flags);
#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
  __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))

extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock);
#define atomic_dec_and_raw_lock(atomic, lock) \
  __cond_lock(lock, _atomic_dec_and_raw_lock(atomic, lock))

extern int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,
     unsigned long *flags);
#define atomic_dec_and_raw_lock_irqsave(atomic, lock, flags) \
  __cond_lock(lock, _atomic_dec_and_raw_lock_irqsave(atomic, lock, &(flags)))

int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
        size_t max_size, unsigned int cpu_mult,
        gfp_t gfp, const char *name,
        struct lock_class_key *key);

#define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
 ({             \
  static struct lock_class_key key;        \
  int ret;           \
              \
  ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
            cpu_mult, gfp, #locks, &key); \
  ret;            \
 })

void free_bucket_spinlocks(spinlock_t *locks);

DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t,
      raw_spin_lock(_T->lock),
      raw_spin_unlock(_T->lock))

DEFINE_LOCK_GUARD_1_COND(raw_spinlock, _try, raw_spin_trylock(_T->lock))

DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,
      raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),
      raw_spin_unlock(_T->lock))

DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t,
      raw_spin_lock_irq(_T->lock),
      raw_spin_unlock_irq(_T->lock))

DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock))

DEFINE_LOCK_GUARD_1(raw_spinlock_bh, raw_spinlock_t,
      raw_spin_lock_bh(_T->lock),
      raw_spin_unlock_bh(_T->lock))

DEFINE_LOCK_GUARD_1_COND(raw_spinlock_bh, _try, raw_spin_trylock_bh(_T->lock))

DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
      raw_spin_lock_irqsave(_T->lock, _T->flags),
      raw_spin_unlock_irqrestore(_T->lock, _T->flags),
      unsigned long flags)

DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try,
    raw_spin_trylock_irqsave(_T->lock, _T->flags))

DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,
      spin_lock(_T->lock),
      spin_unlock(_T->lock))

DEFINE_LOCK_GUARD_1_COND(spinlock, _try, spin_trylock(_T->lock))

DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
      spin_lock_irq(_T->lock),
      spin_unlock_irq(_T->lock))

DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try,
    spin_trylock_irq(_T->lock))

DEFINE_LOCK_GUARD_1(spinlock_bh, spinlock_t,
      spin_lock_bh(_T->lock),
      spin_unlock_bh(_T->lock))

DEFINE_LOCK_GUARD_1_COND(spinlock_bh, _try,
    spin_trylock_bh(_T->lock))

DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
      spin_lock_irqsave(_T->lock, _T->flags),
      spin_unlock_irqrestore(_T->lock, _T->flags),
      unsigned long flags)

DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try,
    spin_trylock_irqsave(_T->lock, _T->flags))

DEFINE_LOCK_GUARD_1(read_lock, rwlock_t,
      read_lock(_T->lock),
      read_unlock(_T->lock))

DEFINE_LOCK_GUARD_1(read_lock_irq, rwlock_t,
      read_lock_irq(_T->lock),
      read_unlock_irq(_T->lock))

DEFINE_LOCK_GUARD_1(read_lock_irqsave, rwlock_t,
      read_lock_irqsave(_T->lock, _T->flags),
      read_unlock_irqrestore(_T->lock, _T->flags),
      unsigned long flags)

DEFINE_LOCK_GUARD_1(write_lock, rwlock_t,
      write_lock(_T->lock),
      write_unlock(_T->lock))

DEFINE_LOCK_GUARD_1(write_lock_irq, rwlock_t,
      write_lock_irq(_T->lock),
      write_unlock_irq(_T->lock))

DEFINE_LOCK_GUARD_1(write_lock_irqsave, rwlock_t,
      write_lock_irqsave(_T->lock, _T->flags),
      write_unlock_irqrestore(_T->lock, _T->flags),
      unsigned long flags)

#undef __LINUX_INSIDE_SPINLOCK_H
#endif /* __LINUX_SPINLOCK_H */