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.NET Forum / Languages / Managed C++ / May 2005WaitForSingleObject blocking
If I have some c++ class exported from a Win32 dll, and from some other console application I created two threads and each thread creates an instance of the exported class. My question is related to using WaitForSingleObject from within the dll class methods and if the two threads called a method in the dll that blocks on WaitForSingleObject for a long time, then are the two instances waiting for each other or if returned from WaitForSingleObject it can continue event if the other thread still blocked on its instance? Thanks Rami > If I have some c++ class exported from a Win32 dll, and from some other > console application I created two threads and each thread creates an [quoted text clipped - 6 lines] > WaitForSingleObject it can continue event if the other thread still > blocked on its instance? The threads wait on the object referred to by the HANDLE that you passed to WFSO to become signaled or for the timeout interval you specified to expire. Exactly what happens when the handle becomes signaled depends on the type of the sync object. For example, only one thread is allowed to acquire a mutex and progress, while the rest remain blocked (modulo non-INFINITE timeout values) until that thread releases it (or terminates, in which case it "abandons" the mutex), at which point, another thread can acquire the mutex.  SignatureDoug Harrison Microsoft MVP - Visual C++ Sorry but I mean that the two threads are calling the same method but from different instances and each instance has its own copy of the sync object. so they are not waiting on the same event but on different evemts. But my question is related to DLL processing, so if one thread is waiting on its own event is the other instances blocked two until the waiting is released or each thread runs in its own processing thread? Regards, Rami > Sorry but I mean that the two threads are calling the same method but > from different instances and each instance has its own copy of the sync [quoted text clipped - 5 lines] > Regards, > Rami Each thread runs independently. If each thread is using a different sync object they do not affect each other. SignatureScott McPhillips [VC++ MVP] > Sorry but I mean that the two threads are calling the same method but > from different instances and each instance has its own copy of the sync [quoted text clipped - 3 lines] > the waiting is released or each thread runs in its own processing > thread? I'm not sure what you think is special about DLLs. They're pretty much just chunks of code and data loaded into your process's address space, though the system does serialize the execution of DllMain functions. As for your sync objects, if the HANDLEs you pass to WFSO refer to different sync objects, no synchronization occurs between the two threads when they call WFSO on their respective HANDLEs. They run independently of one another. SignatureDoug Harrison Microsoft MVP - Visual C++ Thanks for you all, now this is clear Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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