Messages in this thread Patch in this message | | | Date | Sat, 14 Jul 2007 13:16:44 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH -rt 4/5] use migrate_disable for __local_begin |
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* Peter Zijlstra (a.p.zijlstra@chello.nl) wrote: > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > --- > include/asm-i386/local.h | 7 ++++--- > include/asm-x86_64/local.h | 7 ++++--- > 2 files changed, 8 insertions(+), 6 deletions(-) > > Index: linux-2.6/include/asm-i386/local.h > =================================================================== > --- linux-2.6.orig/include/asm-i386/local.h > +++ linux-2.6/include/asm-i386/local.h > @@ -197,11 +197,12 @@ static __inline__ long local_sub_return( > #define __local_begin(__flags) \ > { \ > (__flags) = 0; \ > - preempt_disable(); \ > + migrate_disable(); \
Brrrr. That's wrong. Your non atomic __local*() updates only makes sense when preempt_disable/enable() protects them from concurrent threads on the same CPU, which is not the case of migrate_disable/enable(). This is why I suggest that you use local_begin/end() mapped to migrate_disable/enable() for normal local variables, and, if you really want a __local_begin/end(), then it should be mapped to preempt_disable/enable() and should state that it provides no protection against interrupts.
Mathieu
> } > > -static inline void __local_end(unsigned long flags) { > - preempt_enable(); > +static inline void __local_end(unsigned long flags) > +{ > + migrate_enable(); > } > > /* On x86, these are no better than the atomic variants. */ > Index: linux-2.6/include/asm-x86_64/local.h > =================================================================== > --- linux-2.6.orig/include/asm-x86_64/local.h > +++ linux-2.6/include/asm-x86_64/local.h > @@ -186,11 +186,12 @@ static __inline__ long local_sub_return( > #define __local_begin(__flags) \ > { \ > (__flags) = 0; \ > - preempt_disable(); \ > + migrate_disable(); \ > } > > -static inline void __local_end(unsigned long flags) { > - preempt_enable(); > +static inline void __local_end(unsigned long flags) > +{ > + migrate_enable(); > } > > #define __local_inc(l) local_inc(l) > > -- >
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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