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    SubjectRe: [2.6.23-rt3] NMI watchdog trace of deadlock


    On Sat, 27 Oct 2007, Jaswinder Singh wrote:

    > Hello Ingo,
    > On 10/27/07, Ingo Molnar <> wrote:
    > >
    > > it's not atomic interrupt context but irq thread context - and -rt
    > > remaps kmap_atomic() to kmap() internally.
    > >
    > > the problem seems to be what Mike's patch works around: fiddling with
    > > irq flags in the ntfs code. That fiddling seems quite unnecessary at
    > > first sight.
    > >
    > Is this a nice idea to go inside device drivers and filesystem and
    > make changes in kernel source code to enable RT.

    Actually the question is, is it a nice idea for drivers to disable
    interrupts for no obvious reason. I'm sure you have a reason, but it's not
    obvious to me why. What does it protect? Is it SMP safe?

    When tuning a RT system for the customer, the first thing we recommend is
    to check to make sure all the drivers in use do not disable interrupts.

    > RT related change should be in header files, so that we don't need to
    > make changes for drivers or filesystem source files.
    > And when user will disable RT then these patches will again make problems.
    > We need to find some better alternative.

    We do have the local_irq_save_nort that Mike has posted. This is a simple
    wrapper around local_irq_save that enables it when RT is not configured,
    and is a nop when RT is configured.


    -- Steve

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      Last update: 2007-10-27 15:25    [W:0.021 / U:5.624 seconds]
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