Messages in this thread |  | | | Subject | Re: [patch v3 2/3] percpu_counter: fix code for 32bit systems for UP | | From | Eric Dumazet <> | | Date | Thu, 14 Apr 2011 04:35:30 +0200 |
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Le jeudi 14 avril 2011 à 10:04 +0800, shaohua.li@intel.com a écrit : > pièce jointe document texte brut (percpu-counter-32bits.patch) > percpu_counter.counter is a 's64'. Accessing it in 32-bit system is racing. > we need some locking to protect it otherwise some very wrong value could be > accessed. > > Signed-off-by: Shaohua Li <shaohua.li@intel.com> > --- > include/linux/percpu_counter.h | 37 ++++++++++++++++++++++++++----------- > 1 file changed, 26 insertions(+), 11 deletions(-) > > Index: linux/include/linux/percpu_counter.h > =================================================================== > --- linux.orig/include/linux/percpu_counter.h 2011-04-14 08:50:45.000000000 +0800 > +++ linux/include/linux/percpu_counter.h 2011-04-14 09:09:14.000000000 +0800 > @@ -89,9 +89,20 @@ struct percpu_counter { > s64 count; > }; > > -static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount) > +static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount) > { > +#if BITS_PER_LONG == 32 > + preempt_disable(); > fbc->count = amount; > + preempt_enable(); > +#else > + fbc->count = amount; > +#endif > +} > + > +static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount) > +{ > + percpu_counter_set(fbc, amount); > return 0; > } >
Please dont do this and obfuscate the code.
percpu_counter_init() cannot be racy.
Its like saying spin_lock_init() could be racy.
No other thread/cpu is supposed to use the object if not yet initialized.
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