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    SubjectRe: PROBLEM: kernel oops with g_serial USB gadget on 2.6.30
    On Tuesday 23 June 2009, Marek Szyprowski wrote:
    > /* low_latency means ldiscs work in tasklet context, without
    >  * needing a workqueue schedule ... easier to keep up.
    >  */
    > So in low latency mode calls are made from a tasklet.

    ... and that has, at some point since 2.6.26 or so, become a
    problem that caused oopsing.

    > This is not true in
    > my case, as the S3C OTG UDC driver does all its job in interrupts. This
    > way also a (usb) packet_done callback is done from an interrupt. I expect
    > that g_serial driver interacts with tty layer in that packet_done callback,
    > so this is the source of the problems. I noticed that some other UDC
    > drivers also does all its job from an interrupt, so they also might be
    > affected. How this bug should be properly resolved?

    Change the u_serial.c code so that this newish tty behavior
    stops causing problems: don't set low_latency.

    But also try and sort through any consequences of that, and
    don't forget to update the comments which talk about how the
    low_latency setting is affecting code flow.

    - Dave
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      Last update: 2009-06-23 18:57    [W:0.034 / U:38.024 seconds]
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