Messages in this thread Patch in this message | | | Subject | Re: [PATCH 1/2] asm-generic: rwsem: ensure sem->cnt is only accessed via atomic_long_* | From | Davidlohr Bueso <> | Date | Wed, 26 Feb 2014 21:28:24 -0800 |
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On Fri, 2014-02-21 at 17:22 +0000, Will Deacon wrote: > The asm-generic rwsem implementation directly acceses sem->cnt when > performing a __down_read_trylock operation. Whilst this is probably safe > on all architectures, we should stick to the atomic_long_* API and use > atomic_long_read instead. > > Signed-off-by: Will Deacon <will.deacon@arm.com> > --- > include/asm-generic/rwsem.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h > index bb1e2cdeb9bf..75af612f54f8 100644 > --- a/include/asm-generic/rwsem.h > +++ b/include/asm-generic/rwsem.h > @@ -41,7 +41,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) > { > long tmp; > > - while ((tmp = sem->count) >= 0) { > + while ((tmp = atomic_long_read((atomic_long_t *)&sem->count)) >= 0) {
That's pretty ugly, how about having infinite look and just do the tmp assign separately from the conditional?
It also looks like a cpu_relax() could help here between iterations. Other than that:
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
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