> On Fri, 12 Feb 1999, Ulrich Schmid wrote:
>
> > sem->count sem->waking
> >No process holds the semaphore 1 0
> >Process A acquires the semaphore 0 0
> >Process B calls down_interruptible() -1 0
> >Process B is interrupted and passes
> > waking_non_zero() -1 0
> >Process A calls up() (on another CPU) 0 1
>
> B get wakenup and runs waking_non_zero that sees sem->waking == 1 and so
> do sem->waking-- and then B has no way to runs atomic_inc() because
> waking_non_zero returned 1 (owned the semaphore).
If B runs waking_non_zero before A calls up, it will see sem->waking == 0.
Ulrich Schmid
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