/* 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 … #define LOCK_SECTION_START(extra) … #define LOCK_SECTION_END … #define __lockfunc … /* * 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) … #else #define raw_spin_lock_init … #endif #define raw_spin_is_locked(lock) … #ifdef arch_spin_is_contended #define raw_spin_is_contended(lock) … #else #define raw_spin_is_contended … #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() … #endif #ifdef CONFIG_DEBUG_SPINLOCK extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(…); extern int do_raw_spin_trylock(raw_spinlock_t *lock); extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(…); #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) … #define raw_spin_lock(lock) … #ifdef CONFIG_DEBUG_LOCK_ALLOC #define raw_spin_lock_nested(lock, subclass) … #define raw_spin_lock_nest_lock(lock, nest_lock) … #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 … #define raw_spin_lock_nest_lock … #endif #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) #define raw_spin_lock_irqsave(lock, flags) … #ifdef CONFIG_DEBUG_LOCK_ALLOC #define raw_spin_lock_irqsave_nested(lock, flags, subclass) … #else #define raw_spin_lock_irqsave_nested … #endif #else #define raw_spin_lock_irqsave … #define raw_spin_lock_irqsave_nested … #endif #define raw_spin_lock_irq(lock) … #define raw_spin_lock_bh(lock) … #define raw_spin_unlock(lock) … #define raw_spin_unlock_irq(lock) … #define raw_spin_unlock_irqrestore(lock, flags) … #define raw_spin_unlock_bh(lock) … #define raw_spin_trylock_bh(lock) … #define raw_spin_trylock_irq(lock) … #define raw_spin_trylock_irqsave(lock, flags) … #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) { … } #ifdef CONFIG_DEBUG_SPINLOCK #define spin_lock_init(lock) … #else #define spin_lock_init … #endif static __always_inline void spin_lock(spinlock_t *lock) { … } static __always_inline void spin_lock_bh(spinlock_t *lock) { … } static __always_inline int spin_trylock(spinlock_t *lock) { … } #define spin_lock_nested(lock, subclass) … #define spin_lock_nest_lock(lock, nest_lock) … static __always_inline void spin_lock_irq(spinlock_t *lock) { … } #define spin_lock_irqsave(lock, flags) … #define spin_lock_irqsave_nested(lock, flags, subclass) … static __always_inline void spin_unlock(spinlock_t *lock) { … } static __always_inline void spin_unlock_bh(spinlock_t *lock) { … } static __always_inline void spin_unlock_irq(spinlock_t *lock) { … } static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) { … } static __always_inline int spin_trylock_bh(spinlock_t *lock) { … } static __always_inline int spin_trylock_irq(spinlock_t *lock) { … } #define spin_trylock_irqsave(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) { … } static __always_inline int spin_is_contended(spinlock_t *lock) { … } #define assert_spin_locked(lock) … #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) { … } /* * 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) { … } /* * 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) … 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) … extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock); #define 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) … 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) … 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), … } 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), … } 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), … } 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), … } #undef __LINUX_INSIDE_SPINLOCK_H #endif /* __LINUX_SPINLOCK_H */
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