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    SubjectRe: [BUG] 2.6.37-rc3 massive interactivity regression on ARM
    On Fri, 10 Dec 2010, Peter Zijlstra wrote:

    > > > gcc wont be able to do this yet (%fs/%gs selectors)
    > >
    > > The kernel can do that using the __percpu annotation.
    > That's not true:
    > # define __percpu
    > Its a complete NOP.

    The annotation serves for sparse checking. .... If you do not care about
    those checks then you can simply pass a percpu pointer in the same form as
    a regular pointer.

    > > > But we can provide this_cpu_write_seqcount_{begin|end}()
    > >
    > > No we cannot do hat. this_cpu ops are for per cpu data and not for locking
    > > values shared between processors. We have a mechanism for passing per cpu
    > > pointers with a corresponding annotation.
    > -enoparse, its not locking anything, is a per-cpu sequence count.

    seqlocks are for synchronization of objects on different processors.

    Seems that you do not have that use case in mind. So a seqlock restricted
    to a single processor? If so then you wont need any of those smp write
    barriers mentioned earlier. A simple compiler barrier() is sufficient.

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      Last update: 2010-12-10 20:53    [W:0.044 / U:12.168 seconds]
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