why CCriticalSection::Lock doesn't allow to set the timeout

[Ramon F Mendes]

as far as I know, the only difference between CMutex and CCriticalSection is that CMutex works at the kernel level and so can be used across process boundaries So why can you specify the timeout with CMutex::Lock method, but not in CCriticalSection::Lock?

CMutex mutex;
mutex.Lock( 1000 );

CCriticalSection critsec;
critsec.Lock( 1000 ); //here you will get an assertion

[_Superman_]

At the API level, you can use any of the Wait functions like WaitForSingleObject to wait on a mutex but not on a critical section. That is why the MFC wrappers work in a similar fashion. For a mutex there is an associated handle. But for a critical section there is not handle.

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[Naveen]

midiway wrote:

So why can you specify the timeout with CMutex::Lock method, but not in CCriticalSection::Lock?

Because EnterCriticalSection() API does not accepts a timeout parameter :cool:

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[cmk]

A critical section is a higher level construct than a mutex. The current critical section wraps a semeaphore it uses for locking when it has to wait. Before it waits it will spin in user mode to avoid the costly transition to kernel mode and thread context switch. You have two options to use a timeout with a critical section: 1. (Not recommended) Write a function that uses the internal LockSemaphore. You have to duplicate the functionality for EnterCriticalSection() but allow a timeout to be passed to the wait on the semaphore. 2. Spin on TryEnterCriticalSection. Use GetTickCount to check when you time out. Make sure you do this right. Read up on YieldProcessor, SwitchToThread and Sleep/SleepEx. This is only usefull if you _have to_ use a ctirical section and you _have to_ be able to timeout.

...cmk The idea that I can be presented with a problem, set out to logically solve it with the tools at hand, and wind up with a program that could not be legally used because someone else followed the same logical steps some years ago and filed for a patent on it is horrifying. - John Carmack