OSR's ntdev List: WdfUsbTargetPipeWriteSynchronously thread safety

Message 1 of 3

27 Apr 12 15:26

Frank Jenner

xxxxxx@cspeed.com

Join Date: 27 Jan 2012

Posts To This List: 38

WdfUsbTargetPipeWriteSynchronously thread safety

When writing data to a USB endpoint using WdfUsbTargetPipeWriteSynchronously, is there any guarantee that all of the data pointed to by the MemoryDescriptor parameter will be written to the USB endpoint atomically, or is it possible that concurrent calls to WdfUsbTargetPipeWriteSynchronously to the same endpoint could cause data to be interleaved? My assumption is that, since the memory is contained in a single request to the USB pipe I/O target, the request will be queued up by the I/O target and processed one-at-a-time. On the other hand, if my assumption is wrong, I will surely want to have locks around any such calls to WdfUsbTargetPipeWriteSynchronously.

Message 2 of 3

27 Apr 12 16:00

Doron Holan

xxxxxx@microsoft.com

Join Date: 08 Sep 2005

Posts To This List: 8350

RE: WdfUsbTargetPipeWriteSynchronously thread safety

The memory of the two write requests will not beinterleaved on the usb wire, but the order in which the 2 write calls are processed is not deterministic. If two threads call WriteSynchronously at the same time,d oes it matter if the order is non deterministic? Are the writes stateful? -----Original Message----- From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of xxxxx@cspeed.com Sent: Friday, April 27, 2012 12:26 PM To: Windows System Software Devs Interest List Subject: [ntdev] WdfUsbTargetPipeWriteSynchronously thread safety When writing data to a USB endpoint using WdfUsbTargetPipeWriteSynchronously, is there any guarantee that all of the data pointed to by the MemoryDescriptor parameter will be written to the USB endpoint atomically, or is it possible that concurrent calls to WdfUsbTargetPipeWriteSynchronously to the same endpoint could cause data to be interleaved? My assumption is that, since the memory is contained in a single request to the USB pipe I/O target, the request will be queued up by the I/O target and processed one-at-a-time. On the other hand, if my assumption is wrong, I will surely want to have locks around any such calls to WdfUsbTargetPipeWriteSynchronously. --- 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 3

27 Apr 12 16:09

Frank Jenner

xxxxxx@cspeed.com

Join Date: 27 Jan 2012

Posts To This List: 38

RE: WdfUsbTargetPipeWriteSynchronously thread safety

Thanks! In this application, the memory provided for each call is a self-describing "packet", and the order in which these packets are written does not matter, so long as each one makes it out to the wire uninterrupted.

Posting Rules
You may not post new threads You may not post replies You may not post attachments	You must login to OSR Online AND be a member of the ntdev list to be able to post.

All times are GMT -5. The time now is 01:49.