PREEMPTIVE_OS_QUERYCONTEXTATTRIBUTES

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Description:

This wait type is when a thread is calling the Windows QueryContextAttributes function.

(Books Online description: N/A)

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Added in SQL Server version:

2012

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 423 in 2012 and 439 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.

Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as RUNNING, as SQL Server doesn’t know what Windows is doing with the thread.

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

1. Getting security information (in this case, while processing a new client connection)
2. Getting security information (in this case, while resetting a connection from a connection pool)

And other similar call stacks.

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

1. SOS_Task::PopWait+b1
   SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
   SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+5d
   FInterrogateLogin+583
   FindLogin+23b
   login+829
   process_login_finish+16e
   process_commands+456
   TDSSNIClient::AddSSPIProviderHandler+474
   TDSSNIClient::AddProviderHandler+38
   SNIProcessAddProviderOnWorker+122
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab
2. SOS_Task::PopWait+b1
   SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
   SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+5d
   FInterrogateLogin+583
   FindLogin+23b
   FRedoLoginImpl+80d
   ResetConnAndRedoLogin+231
   process_request+3c6
   process_commands+4a3
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab