linux原子操作.docx

在linux2.6.18之后，删除了asm/atomic.h和asm/bitops.h头文件，编译器提供内建（built-in）原子操作函数。需要在gcc编译选项中指明CPU类型。如gcc -marth=i686 -o hello hello.c。type可以是以下类型:intunsigned intlongunsigned longlong longunsigned long long以下函数返回修改之前的值：type __sync_fetch_and_add (type *ptr, type value);type __sync_fetch_and_sub (type *ptr, type value);type __sync_fetch_and_or (type *ptr, type value);type __sync_fetch_and_and (type *ptr, type value);type __sync_fetch_and_xor (type *ptr, type value);type __sync_fetch_and_nand (type *ptr, type value);以下函数返回修改之后的值：type __sync_add_and_fetch (type *ptr, type value);type __sync_sub_and_fetch (type *ptr, type value);type __sync_or_and_fetch (type *ptr, type value);type __sync_and_and_fetch (type *ptr, type value);type __sync_xor_and_fetch (type *ptr, type value);type __sync_nand_and_fetch (type *ptr, type value);更多信息：Built-in functions for atomic memory accessThe following builtins are intended to be compatible with those described in the Intel Itanium Processor-specific Application Binary Interface, section 7.4. As such, they depart from the normal GCC practice of using the “__builtin_” prefix, and further that they are overloaded such that they work on multiple types. The definition given in the Intel documentation allows only for the use of the types int, long, long long as well as their unsigned counterparts. GCC will allow any integral scalar or pointer type that is 1, 2, 4 or 8 bytes in length. Not all operations are supported by all target processors. If a particular operation cannot be implemented on the target processor, a warning will be generated and a call an external function will be generated. The external function will carry the same name as the builtin, with an additional suffix `_n where n is the size of the data type. In most cases, these builtins are considered a full barrier. That is, no memory operand will be moved across the operation, either forward or backward. Further, instructions will be issued as necessary to prevent the processor from specu