KeWaitForSingleObject in Completion/Cancellation Routine
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From: Prakash Manannavar on 19 Nov 2009 06:21 Hi all, Is it a right thing to wait for an event with KeWaitForSingleObject in the Completion/Cancellation Routine? In DDK reference, it has been told that, caller for KeWaitForSingleObject can run at IRQL <= DISPATCH_LEVEL. Even Cancell routines will run at IRQL <= DISPATCH_LEVEL. -- ~~~~~ Prakash A Manannavar, Bangalore/Bengaluru.
From: Scott Noone on 19 Nov 2009 08:11 > Is it a right thing to wait for an event with KeWaitForSingleObject in the > Completion/Cancellation Routine? No, that is not a good idea. As you noted this may break the IRQL rules as completion/cancel routines can be called at IRQL DISPATCH_LEVEL. -- Scott Noone Consulting Associate OSR Open Systems Resources, Inc. http://www.osronline.com "Prakash Manannavar" <PrakashManannavar(a)discussions.microsoft.com> wrote in message news:8488E223-4807-4EA5-A58F-299EA6E0DC9A(a)microsoft.com... > Hi all, > > > Is it a right thing to wait for an event with KeWaitForSingleObject in the > Completion/Cancellation Routine? > > In DDK reference, it has been told that, caller for KeWaitForSingleObject > can run at IRQL <= DISPATCH_LEVEL. Even Cancell routines will run at IRQL > <= > DISPATCH_LEVEL. > -- > ~~~~~ > Prakash A Manannavar, > Bangalore/Bengaluru.
From: Prakash Manannavar on 20 Nov 2009 00:18 Thanks Scott, I have some issues, 1. If waiting with KeWaitForSingleObejct at IRQL <= DISPATCH_LEVEL, Is there any specific reason which has been supported by OS? 2. I read KeRaiseIrql and KeLowerIrql functions, As I read we can raise IRQL first and then we can lower it to the previous level. Is there any functions to lower the IRQL and then raise it to the previous level? -- ~~~~~ Prakash A Manannavar, Bangalore/Bengaluru.
From: David Craig on 20 Nov 2009 00:49 NO!!! That will/can cause priority inversion. "Prakash Manannavar" <PrakashManannavar(a)discussions.microsoft.com> wrote in message news:BAD738A5-ECE4-4D4B-8CA5-588A2232CD9D(a)microsoft.com... > Thanks Scott, > > I have some issues, > > 1. If waiting with KeWaitForSingleObejct at IRQL <= DISPATCH_LEVEL, Is > there > any specific reason which has been supported by OS? > > 2. I read KeRaiseIrql and KeLowerIrql functions, As I read we can raise > IRQL > first and then we can lower it to the previous level. Is there any > functions > to lower the IRQL and then raise it to the previous level? > > -- > ~~~~~ > Prakash A Manannavar, > Bangalore/Bengaluru. >
From: Tim Roberts on 20 Nov 2009 01:59
Prakash Manannavar <PrakashManannavar(a)discussions.microsoft.com> wrote: > >2. I read KeRaiseIrql and KeLowerIrql functions, As I read we can raise IRQL >first and then we can lower it to the previous level. Is there any functions >to lower the IRQL and then raise it to the previous level? Think about what you're asking. The reason you run at an increased IRQL is to make sure your code can't be interrupted by lower level code. AS SOON AS you lower your IRQL, your code will be interrupted by lower level code. The RIGHT way do to this is to queue up a work item with IoQueueWorkItem. The callback will be called at PASSIVE_LEVEL. -- Tim Roberts, timr(a)probo.com Providenza & Boekelheide, Inc. |