OSR's ntdev List: Is a Remove Lock needed even in a simple dispatch routine?

Message 1 of 4

03 Jul 12 22:59

David F.

xxxxxx@terabyteunlimited.com

Join Date: 12 Jan 2012

Posts To This List: 59

Is a Remove Lock needed even in a simple dispatch routine?

Is the remove lock actually needed in the sample below? I know it would be needed if there was a completion routine setup, but in this case, it's just a simple forward. TIA!! NTSTATUS DispatchRead(IN PDEVICE_OBJECT fido, PIRP irp) { // Make sure device doesn't get deleted on a removal request psDeviceExtension pdx=(psDeviceExtension) fido->DeviceExtension; NTSTATUS status=IoAcquireRemoveLock(&pdx->RemoveLock, irp); if (!NT_SUCCESS(status)) { // Device waiting to being deleted so complete with STATUS_DELETE_PENDING return(CompleteRequest(irp, status, 0)); } // Pass this through to next driver to handle request IoSkipCurrentIrpStackLocation(irp); status=IoCallDriver(pdx->LowerDeviceObject, irp); // Release the lock and exit IoReleaseRemoveLock(&pdx->RemoveLock, irp); return(status); }

Message 2 of 4

03 Jul 12 23:07

Doron Holan

xxxxxx@microsoft.com

Join Date: 08 Sep 2005

Posts To This List: 8350

RE: Is a Remove Lock needed even in a simple dispatch routine?

Are you filtering a stack with only handle based io? If yes, you don't need a remlock. If you are filtering a stack where non handle based io is sent, a remlock is usually a good idea. d -----Original Message----- From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of xxxxx@terabyteunlimited.com Sent: Tuesday, July 03, 2012 7:58 PM To: Windows System Software Devs Interest List Subject: [ntdev] Is a Remove Lock needed even in a simple dispatch routine? Is the remove lock actually needed in the sample below? I know it would be needed if there was a completion routine setup, but in this case, it's just a simple forward. TIA!! NTSTATUS DispatchRead(IN PDEVICE_OBJECT fido, PIRP irp) { // Make sure device doesn't get deleted on a removal request psDeviceExtension pdx=(psDeviceExtension) fido->DeviceExtension; NTSTATUS status=IoAcquireRemoveLock(&pdx->RemoveLock, irp); if (!NT_SUCCESS(status)) { // Device waiting to being deleted so complete with STATUS_DELETE_PENDING return(CompleteRequest(irp, status, 0)); } // Pass this through to next driver to handle request IoSkipCurrentIrpStackLocation(irp); status=IoCallDriver(pdx->LowerDeviceObject, irp); // Release the lock and exit IoReleaseRemoveLock(&pdx->RemoveLock, irp); return(status); } --- NTDEV is sponsored by OSR For our schedule of WDF, WDM, debugging and other seminars visit: http://www.osr.com/seminars To unsubscribe, visit the List Server section of OSR Online at http://www.osronline.com/page.cfm?name=ListServer

Message 3 of 4

03 Jul 12 23:53

David F.

xxxxxx@terabyteunlimited.com

Join Date: 12 Jan 2012

Posts To This List: 59

RE: Is a Remove Lock needed even in a simple dispatch routine?

The disk drive stack so I presume that is handle only based IO and therefore a remove lock is not needed unless setting up a completion routine? >Are you filtering a stack with only handle based io? If yes, you don't need a remlock. >If you are filtering a stack where non handle based io is sent, a remlock is >usually a good idea.

Message 4 of 4

06 Jul 12 13:37

David F.

xxxxxx@terabyteunlimited.com

Join Date: 12 Jan 2012

Posts To This List: 59

RE: Is a Remove Lock needed even in a simple dispatch routine?

Can someone confirm the presumption above? Because it differs from what others have written which suggest you must do the remove lock before IoCallDriver and then unlock after, even if no completion routine?

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