Re: Deadlock on the mm->mmap_sem

Andrea Arcangeli
2001-09-20T02:07:16Z

On Wed, Sep 19, 2001 at 08:19:09PM +0200, Manfred Spraul wrote:
> > if we go generic then I strongly recommend my version of the generic
> > semaphores is _much_ faster (and cleaner) than this one (it even
> allows
> > more than 2^31 concurrent readers on 64 bit archs ;).
> >
> Andrea,
>
> implementing recursive semaphores is trivial, but do you have any idea
> how to fix the latency problem?

yes, one solution to the latency problem without writing the
ugly code would be simply to add a per-process counter to pass to a
modified rwsem api, then to hide the trickery in a mm_down_read macro.
such way it will be recursive _and_ fair.

Andrea