Forcing Printer Handle Thread Safety

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When working with printer handles in an application obtained from functions such as OpenPrinter and CreateDC,
it is the caller’s responsibility to only access the object from one thread at a time. This should always be followed
when developing new code. 

If you’re stuck with some code that doesn’t respect this and accesses the object on multiple threads concurrently as
a race condition, there is something that you can try that may help the issue. There is a registry key that will cause
the spooler subsystem to forcibly restrict access to the object to one thread at a time. This will have a performance
penalty, so it’s definitely not desirable unless absolutely needed. In order to make this behavior change, set
the registry key as indicated below and restart the spooler service:

 

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print]
"SynchronousPrintHandleAccessMode"=dword:00000001

 

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