On Wed, 16 May 2007 07:41:26 -0700, David Brownell <[EMAIL PROTECTED]> wrote:
> > in that when you have > > pre-allocated all buffers and all USB host controller descriptors, you will > > never get in the situation of not being able to allocate transfer > > descriptors > > on the fly, like done on Linux. > > That's not a failure mode that's been often observed on Linux. (Never, > in my own experience... which I admit has not focussed on that particular > type of stress load.) So it's hard to argue that it should motivate a > redesign of core APIs. I have never, ever, seen USB stack deplete the atomic pool completely either, if this is what you are talking about. So, you're quite right about that. However, the usb-storage worker thread can get stuck sleeping for allocations. We try to deal with it by using GFP_NOIO carefuly, but this is a palliative. I continue to hear from my users with systems locking up when they mount ext3 on winchesters in USB enclosures and use a simple cp. Switching from usb-storage to ub fixes the issue (which is why we continue to ship it). It's not a commonplace concern, but it persists. Sometimes it involves scsi_eh_0. I have come to think that ub does not dramatically alter the pressure on the atomic pool. It allocates the same QHs and TDs. It's the thread which is the main problem, because it allows for interesting scenarios of deadlocks between kswapd, scsi_eh_0, and usb-storage helper. I am thinking about taking the ub concept and integrating it into usb-storage as some kind of "threadless" option. If only I could get rid of the SCSI error handling... -- Pete ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
