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Exactly as described below.

(Books Online description: “Occurs when a task is currently performing CLR execution and is waiting to enter a critical section of the task that is currently being used by another task.”)

Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.

Added in SQL Server version:


Removed in SQL Server version:


Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 215 in 2008 and 2008 R2, 222 in 2012, and 229 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

I have not seen this wait type be a noticeable contention point. I would imagine that if this wait type becomes prevalent on your system, you should investigate critical sections in your CLR code to determine if a thread could remain in the section for a long time.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for access to a critical section while creating an assembly

And other similar call stacks, depending on the CLR assemblies in use.

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PostWait+4d
    UnfairRecursiveMutexInternal<Spinlock<153,1,0> >::LongWait+191
    WaitWrapper<UnfairRecursiveMutexInternal<Spinlock<153,1,0> > >+a1
    HostWait<UnfairRecursiveMutexInternal<Spinlock<153,1,0> > >+a1
    CHostCrstBase<UnfairRecursiveMutexInternal<Spinlock<153,1,0> >,SOS_DDRecursiveMutex>::WaitInternal+79
    CHostCrstBaseWrapper<UnfairRecursiveMutexInternal<Spinlock<153,1,0> >,SOS_DDRecursiveMutex>::Enter+7a