Messages in this thread Patch in this message | | | Date | Tue, 17 May 2011 16:41:18 +0800 | From | Shaohua Li <> | Subject | [patch v3 1/3] percpu_counter: fix code for 32bit systems for UP |
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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 | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-)
Index: linux/include/linux/percpu_counter.h =================================================================== --- linux.orig/include/linux/percpu_counter.h 2011-05-05 10:33:12.000000000 +0800 +++ linux/include/linux/percpu_counter.h 2011-05-06 11:19:26.000000000 +0800 @@ -101,14 +101,34 @@ static inline void percpu_counter_destro 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 s64 percpu_counter_read(struct percpu_counter *fbc) +{ +#if BITS_PER_LONG == 32 + s64 count; + preempt_disable(); + count = fbc->count; + preempt_enable(); + return count; +#else + return fbc->count; +#endif } static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs) { - if (fbc->count > rhs) + s64 count = percpu_counter_read(fbc); + if (count > rhs) return 1; - else if (fbc->count < rhs) + else if (count < rhs) return -1; else return 0; @@ -128,18 +148,13 @@ __percpu_counter_add(struct percpu_count percpu_counter_add(fbc, amount); } -static inline s64 percpu_counter_read(struct percpu_counter *fbc) -{ - return fbc->count; -} - /* * percpu_counter is intended to track positive number. In UP case, the number * should never be negative. */ static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc) { - return fbc->count; + return percpu_counter_read(fbc); } static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
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