root/include/asm-generic/local.h

INCLUDED FROM

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_GENERIC_LOCAL_H
   3 #define _ASM_GENERIC_LOCAL_H
   4 
   5 #include <linux/percpu.h>
   6 #include <linux/atomic.h>
   7 #include <asm/types.h>
   8 
   9 /*
  10  * A signed long type for operations which are atomic for a single CPU.
  11  * Usually used in combination with per-cpu variables.
  12  *
  13  * This is the default implementation, which uses atomic_long_t.  Which is
  14  * rather pointless.  The whole point behind local_t is that some processors
  15  * can perform atomic adds and subtracts in a manner which is atomic wrt IRQs
  16  * running on this CPU.  local_t allows exploitation of such capabilities.
  17  */
  18 
  19 /* Implement in terms of atomics. */
  20 
  21 /* Don't use typedef: don't want them to be mixed with atomic_t's. */
  22 typedef struct
  23 {
  24         atomic_long_t a;
  25 } local_t;
  26 
  27 #define LOCAL_INIT(i)   { ATOMIC_LONG_INIT(i) }
  28 
  29 #define local_read(l)   atomic_long_read(&(l)->a)
  30 #define local_set(l,i)  atomic_long_set((&(l)->a),(i))
  31 #define local_inc(l)    atomic_long_inc(&(l)->a)
  32 #define local_dec(l)    atomic_long_dec(&(l)->a)
  33 #define local_add(i,l)  atomic_long_add((i),(&(l)->a))
  34 #define local_sub(i,l)  atomic_long_sub((i),(&(l)->a))
  35 
  36 #define local_sub_and_test(i, l) atomic_long_sub_and_test((i), (&(l)->a))
  37 #define local_dec_and_test(l) atomic_long_dec_and_test(&(l)->a)
  38 #define local_inc_and_test(l) atomic_long_inc_and_test(&(l)->a)
  39 #define local_add_negative(i, l) atomic_long_add_negative((i), (&(l)->a))
  40 #define local_add_return(i, l) atomic_long_add_return((i), (&(l)->a))
  41 #define local_sub_return(i, l) atomic_long_sub_return((i), (&(l)->a))
  42 #define local_inc_return(l) atomic_long_inc_return(&(l)->a)
  43 
  44 #define local_cmpxchg(l, o, n) atomic_long_cmpxchg((&(l)->a), (o), (n))
  45 #define local_xchg(l, n) atomic_long_xchg((&(l)->a), (n))
  46 #define local_add_unless(l, _a, u) atomic_long_add_unless((&(l)->a), (_a), (u))
  47 #define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a)
  48 
  49 /* Non-atomic variants, ie. preemption disabled and won't be touched
  50  * in interrupt, etc.  Some archs can optimize this case well. */
  51 #define __local_inc(l)          local_set((l), local_read(l) + 1)
  52 #define __local_dec(l)          local_set((l), local_read(l) - 1)
  53 #define __local_add(i,l)        local_set((l), local_read(l) + (i))
  54 #define __local_sub(i,l)        local_set((l), local_read(l) - (i))
  55 
  56 #endif /* _ASM_GENERIC_LOCAL_H */