Re: [ofa-general] Re: [GIT PULL] please pull ummunotify

Pavel Machek
2009-09-28T20:49:23Z

On Tue 2009-09-15 07:57:56, Roland Dreier wrote:
>
> > I don't remember seeing discussion of this on lkml. Yes it is in
> > -next...
>
> eg http://lkml.org/lkml/2009/7/31/197 and followups, or search for v2
> and earlier patches.

Well... it seems little overspecialized. Just modifying libc to
provide hooks you want looks like better solution.

> > Basically it allows app to 'trace itself'? ...with interesting mmap()
> > interface, exporting int to userspace, hoping it behaves atomically...?
>
> Yes, it allows app to trace what the kernel does to memory mappings. I
> don't believe there's any real issue to atomicity of mmap'ed memory,
> since userspace really just tests whether read value is == to old read
> value or not.

That still needs memory barriers etc.. to ensure reliable operation,
no?
Pavel

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