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kernel/include/linux/spinlock.h

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/* 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_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_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 */
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