[Bugme-new] [Bug 8882] New: 100% CPU for iowait in USB storage devices

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=8882

           Summary: 100% CPU for iowait in USB storage devices
           Product: Drivers
           Version: 2.5
     KernelVersion: 2.6
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: USB
        AssignedTo: greg at kroah.com
        ReportedBy: izaera at autentia.com


Most recent kernel where this bug did not occur:
Distribution: Debian testing
Hardware Environment: happens in three different computers
Software Environment: 
Problem Description: 
When I read from USB disks, CPU usage goes to near 100% for iowait, as shown in
top. It happens in an AMD64 desktop with USB 2.0, in a Pentium III desktop with
USB 1.0, and also in a Centrino laptop with USB 2.0.

It happens with an SD card USB adapter and also with a SATA disk USB adapter. 

I don't know if this is the expected behaviour for USB device in Linux but
seems strange to me that I cannot use an USB disk to, for example, store DivX
movies and play them.

I have Googled this problem but cannot find any information of help. Please
tell me if this is the expected behaviour or if it is a bug.

In case of a bug I can try any patches or solutions you tell me.

Thanks in advance.

Steps to reproduce: plug in an USB disk and copy a big file to, for example,
/dev/null


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