Messages in this thread | | | Subject | Re: [PATCH 3/4]percpu_counter: fix code for 32bit systems | From | Eric Dumazet <> | Date | Tue, 12 Apr 2011 11:03:55 +0200 |
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Le mardi 12 avril 2011 à 16:04 +0800, Shaohua Li a écrit : > 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 | 43 +++++++++++++++++++++++++++++++---------- > 1 file changed, 33 insertions(+), 10 deletions(-) > > Index: linux/include/linux/percpu_counter.h > =================================================================== > --- linux.orig/include/linux/percpu_counter.h 2011-04-12 15:48:44.000000000 +0800 > +++ linux/include/linux/percpu_counter.h 2011-04-12 15:48:54.000000000 +0800 > @@ -54,7 +54,15 @@ static inline s64 percpu_counter_sum(str > > static inline s64 percpu_counter_read(struct percpu_counter *fbc) > { > +#if BITS_PER_LONG == 32 > + s64 count; > + spin_lock(&fbc->lock); > + count = fbc->count; > + spin_unlock(&fbc->lock); > + return count; > +#else > return fbc->count; > +#endif > } >
Hmm... did you test this with LOCKDEP on ?
You add a possible deadlock here.
Hint : Some percpu_counter are used from irq context.
This interface assumes caller take the appropriate locking.
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