在07-12-15，Xiao-Feng Li <[EMAIL PROTECTED]> 写道： > > On Dec 15, 2007 2:33 PM, 史成荣 <[EMAIL PROTECTED]> wrote: > > I still have 2 questions. > > > > First, I know in the Thread Manager, it is the > > hythread_thin_monitor_try_enter method to aquire the mutex lock > > and implement the *memory barrier.* But* *I looked into the code of this > > method, didn't find any memory barrier operations(including the > > apr_memory_rw_barrier() call and cmpxchg operation) when it is the fat > > lock. when aquiring the fat lock, it calls the > hythread_monitor_try_enter > > method. In the hythread_monitor_try_enter method* there isn't *memory > > barrier operations, but has a call of the *hymutex_trylock* method. Does > the > > hymutex_trylock method also has barrier effect built-in? > > > > Second, when exit the synchoronized area, it should release the mutex > lock > > and flush the local memory to the main memory. But the > > hythread_thin_monitor_exit method only release the mutex lock and I > don't > > find any flushing operation in hythread_thin_monitor_exit method. > > > Chengrong, you have good questions. Your questions are related to > processor memory model, or how to map Java memory model to the > processor. For example, if the processor has sequential consistency, > there is no need for any extra flushing operation because all the > local memory operations enter the system memory hierarchy in order of > issuing. X86 processors use "processor consistency" which is weaker > than sequential consistency, so it has xfence instructions for the > purpose. > > So to really understand the issues, you probably can read some > materials on processor architecture, esp. the memory model part. There > are chapters in "Computer architecture, a quantitative approach" or > "Parallel architecture: a hardware/software interface". For a specific > processor type, you can read its architecture manual to understand its > behavior in SMP configuration. For example, "lock" prefix in X86 > processor has both barrier and flushing effects.
Do you mean it is OK that there is no flushing operation when exiting the synchronized area? Or I missed the flushing opertions? Thanks, > xiaofeng > > > > I think there must be some mistakes of my idea, hoping for your advice. > > > > > > > > > Thanks, > > > Chengrong > > > > > > > > > > > > > > > > > > -- > http://xiao-feng.blogspot.com >
