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A spin lock is exactly what it sounds like.

OK, let’s switch gears slightly and discuss the three types of spin lock mentioned above. Acquire and release at IRQL < = APC_LEVEL Not recursive / Release on the same thread or on a different threadĪcquisition does not change IRQL. Wait at IRQL <= APC_LEVEL and signal at IRQL <= DISPATCH_LEVEL Synchronization event (kernel dispatcher object)Īcquisition does not change IRQL. Recursive / Release on same thread as acquire Not recursive / Release on same thread as acquireĪcquisition raises IRQL to DISPATCH_LEVEL and returns previous IRQL to callerĪcquisition raises IRQL to DISPATCH_LEVEL and stores previous IRQL in lock owner handleĪcquisition raises IRQL to APC_LEVEL and stores previous IRQL in lockĮnters critical region upon acquisition and leaves critical region upon release However, here are the different types of Windows mutex as listed on MSDN: Type of MutexĪcquisition raises IRQL to DIRQ and returns previous IRQL to caller What happens to a mutex if the thread that is holding it is terminated?Īs with our last two posts, we’re not going to delve too deeply into programming concepts.Can the mutex be acquired by a thread more than once without releasing it (i.e.Must the mutex be released on the same thread that acquired it?.Does acquiring the mutex raise the current IRQL?.

At what IRQL can the mutex be acquired and released?.

There are different types of mutexes – and determining which one will be used is based on a number of factors, including: Essentially any lock that grants mutually exclusive access is a mutex. In other words, while one thread has the mutex, all other threads are prevented from using it. Mutexes ensure mutually exclusive (hence the term) access. Good Morning AskPerf! We’re continuing on with our mini-series on Synchronization Mechanisms today with a look at Mutexes.