"Kevin P. Fleming" <kpfleming@xxxxxxxxxxxxxxx> writes: > Ian Lance Taylor wrote: > > That means that the only correct way to share a memory buffer between > > threads is to use a mutex, and it means that the mutex code can not be > > written in standard conformant C. The mutex code must use asm > > statements to insert memory barriers as required (on the x86 a lock > > prefix serves as a memory barrier (except that some specific x86 > > processors have bugs, but I digress...)). > > This comment makes me curious, since I see (and work on) plenty of code > that shares data structures between threads using only a mutex for > protection and no memory barrier instructions of any kind. This code is > using standard POSIX threading constructs and seems to work fine on > multi-CPU and multi-core systems, both x86 and other flavors. The mutex code itself, assuming it is written correctly, provides the required memory barriers. > Are you referring to a specific sort of memory sharing between threads > here, or are you saying that you think that _all_ objects shared between > threads need to be protected in this way? All objects shared between threads need to protected by a mutex, or by some other type of memory barrier. Ian
