a question about multiplethread

[pengsenl]

now i use several threads to wite a serial port ,i want only one thread to write the port at the same time ,I don't know how to do it . i hope some one help me soon

[Vanaj]

Take a look at Mutex's and Critical Sections.

[Siddhartha]

[ redirected ]

Regards,
Siddhartha

[Siddhartha]

The easiest approach to restricting the number of threads that execute a piece of code to one is via Critical Sections.


Critical Section Objects (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/critical_section_objects.asp)
One works with Critical Sections using Win APIs -

InitializeCriticalSection (http://msdn.microsoft.com/library/en-us/dllproc/base/initializecriticalsection.asp)
EnterCriticalSection (http://msdn.microsoft.com/library/en-us/dllproc/base/entercriticalsection.asp)
LeaveCriticalSection (http://msdn.microsoft.com/library/en-us/dllproc/base/leavecriticalsection.asp)
DeleteCriticalSection (http://msdn.microsoft.com/library/en-us/dllproc/base/deletecriticalsection.asp)


Sample: Using Critical Sections (http://msdn.microsoft.com/library/en-us/dllproc/base/using_critical_section_objects.asp)
So, in your case, the code would be something like this -

Creating and Initializing:
// A global object, or a globally accessible object (like static member)
CRITICAL_SECTION myCS;

// In the main thread
::InitializeCriticalSection (&myCS); Using Critical Sections:
// Inside the worker thread

// At the point in code that needs to be protected
// And needs to be entered one thread at a time

::EnterCriticalSection (&myCS);

// The lines of code that need to be protected

::LeaveCriticalSection (&myCS); Finally, Deleting:
// Again in the main thread, after the worker threads
// Have ended and the CS is not needed
::DeleteCriticalSection (&myCS); Hope, you now have a clear idea of the way to proceed.