root/arch/sh/include/asm/spinlock-cas.h

INCLUDED FROM

DEFINITIONS

1. __sl_cas
2. arch_spin_lock
3. arch_spin_unlock
4. arch_spin_trylock
5. arch_read_lock
6. arch_read_unlock
7. arch_write_lock
8. arch_write_unlock
9. arch_read_trylock
10. arch_write_trylock

   1 /* SPDX-License-Identifier: GPL-2.0
   2  *
   3  * include/asm-sh/spinlock-cas.h
   4  *
   5  * Copyright (C) 2015 SEI
   6  */
   7 #ifndef __ASM_SH_SPINLOCK_CAS_H
   8 #define __ASM_SH_SPINLOCK_CAS_H
   9 
  10 #include <asm/barrier.h>
  11 #include <asm/processor.h>
  12 
  13 static inline unsigned __sl_cas(volatile unsigned *p, unsigned old, unsigned new)
  14 {
  15         __asm__ __volatile__("cas.l %1,%0,@r0"
  16                 : "+r"(new)
  17                 : "r"(old), "z"(p)
  18                 : "t", "memory" );
  19         return new;
  20 }
  21 
  22 /*
  23  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  24  */
  25 
  26 #define arch_spin_is_locked(x)          ((x)->lock <= 0)
  27 
  28 static inline void arch_spin_lock(arch_spinlock_t *lock)
  29 {
  30         while (!__sl_cas(&lock->lock, 1, 0));
  31 }
  32 
  33 static inline void arch_spin_unlock(arch_spinlock_t *lock)
  34 {
  35         __sl_cas(&lock->lock, 0, 1);
  36 }
  37 
  38 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  39 {
  40         return __sl_cas(&lock->lock, 1, 0);
  41 }
  42 
  43 /*
  44  * Read-write spinlocks, allowing multiple readers but only one writer.
  45  *
  46  * NOTE! it is quite common to have readers in interrupts but no interrupt
  47  * writers. For those circumstances we can "mix" irq-safe locks - any writer
  48  * needs to get a irq-safe write-lock, but readers can get non-irqsafe
  49  * read-locks.
  50  */
  51 
  52 static inline void arch_read_lock(arch_rwlock_t *rw)
  53 {
  54         unsigned old;
  55         do old = rw->lock;
  56         while (!old || __sl_cas(&rw->lock, old, old-1) != old);
  57 }
  58 
  59 static inline void arch_read_unlock(arch_rwlock_t *rw)
  60 {
  61         unsigned old;
  62         do old = rw->lock;
  63         while (__sl_cas(&rw->lock, old, old+1) != old);
  64 }
  65 
  66 static inline void arch_write_lock(arch_rwlock_t *rw)
  67 {
  68         while (__sl_cas(&rw->lock, RW_LOCK_BIAS, 0) != RW_LOCK_BIAS);
  69 }
  70 
  71 static inline void arch_write_unlock(arch_rwlock_t *rw)
  72 {
  73         __sl_cas(&rw->lock, 0, RW_LOCK_BIAS);
  74 }
  75 
  76 static inline int arch_read_trylock(arch_rwlock_t *rw)
  77 {
  78         unsigned old;
  79         do old = rw->lock;
  80         while (old && __sl_cas(&rw->lock, old, old-1) != old);
  81         return !!old;
  82 }
  83 
  84 static inline int arch_write_trylock(arch_rwlock_t *rw)
  85 {
  86         return __sl_cas(&rw->lock, RW_LOCK_BIAS, 0) == RW_LOCK_BIAS;
  87 }
  88 
  89 #endif /* __ASM_SH_SPINLOCK_CAS_H */