#include <libc.h>

 int ainc(long *p)

 int adec(long *p)

 int cas(uint *p, int ov, int nv)

 int casp(void **p, void *ov, void *nv)

 int casl(ulong *p, ulong ov, ulong nv)

 int cas32(u32int *p, u32int ov, u32int nv)

 int cas64(u64int *p, u64int ov, u64int nv)

 void mfence(void)
 DESCRIPTION
These functions provide access to atomic operations, useful for
synchronization.

 Ainc and
 adec atomically
increment and decrement (respectively) the integer pointed to by
 p , and return the resulting value after the operation.
On architectures with a weak memory model, both operations
are implemented with a barrier to memory reordering.
In other words, all loads and stores
which precede the increment / decrement in program order
will be observed before it,
and the increment / decrement will be observed before any loads
and stores which follow it in program order.

 Cas performs a compare and swap on the word pointed to by
 p , provided that the value is still
 ov (the old value), so that the new value is
 nv . Functions
 cas32 ,  cas64 ,  casp , and
 casul do the same for 32-bit values, 64-bit values, pointers, and unsigned long
integers.

 Mfence sets a memory fence so that all outstanding memory operations are performed
before returning from it.
 SOURCE
 /sys/src/libc/386/atom.s 

 /sys/src/libc/amd64/atom.s 
 SEE ALSO
 incref (2). 
 BUGS
Some of them may not be implemented for some architectures.