IoCompleteRequest and DIRQL

NTDEV
1

Hi,

IRQLs are numbers representing importance of CPU activity. As we are aware of DISPATCH_LEVEL.
But one statment that I can come across that need explanation from experts :

Why IoCompleteRequest () can not be called at DIRQL and significance of DIRQL ?

Waiting for reply

8^)
Rajesh Nikam

2

Simple answer:

For the same reasons that you cannot set an event at high IRQL. Among the many reasons are that the kernel cannot queue an APC upon processing the completion of the request b/c queueing an APC can only be done at IRQL <= DISPATCH. Almost all of the locks in the system are designed to be acquired at IRQL <= dispatch, having them sync to high irql would be a drastic reduction in performance.

d

From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of Rajesh Nikam
Sent: Wednesday, November 24, 2004 9:12 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] IoCompleteRequest and DIRQL

Hi,
?
IRQLs are numbers representing importance of CPU activity. As we are aware of DISPATCH_LEVEL.
But one statment that I can come across that need explanation from experts :
?
Why IoCompleteRequest () can not be called at DIRQL and significance of DIRQL ?
?
Waiting for reply
?
8^)
Rajesh Nikam
?
?

Questions? First check the Kernel Driver FAQ at http://www.osronline.com/article.cfm?id=256

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