Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 | #ifndef _LINUX_PERCPU_COUNTER_H #define _LINUX_PERCPU_COUNTER_H /* * A simple "approximate counter" for use in ext2 and ext3 superblocks. * * WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4. */ #include <linux/config.h> #include <linux/spinlock.h> #include <linux/smp.h> #include <linux/threads.h> #include <linux/percpu.h> #ifdef CONFIG_SMP struct percpu_counter { spinlock_t lock; long count; long *counters; }; #if NR_CPUS >= 16 #define FBC_BATCH (NR_CPUS*2) #else #define FBC_BATCH (NR_CPUS*4) #endif static inline void percpu_counter_init(struct percpu_counter *fbc) { spin_lock_init(&fbc->lock); fbc->count = 0; fbc->counters = alloc_percpu(long); } static inline void percpu_counter_destroy(struct percpu_counter *fbc) { free_percpu(fbc->counters); } void percpu_counter_mod(struct percpu_counter *fbc, long amount); static inline long percpu_counter_read(struct percpu_counter *fbc) { return fbc->count; } /* * It is possible for the percpu_counter_read() to return a small negative * number for some counter which should never be negative. */ static inline long percpu_counter_read_positive(struct percpu_counter *fbc) { long ret = fbc->count; barrier(); /* Prevent reloads of fbc->count */ if (ret > 0) return ret; return 1; } #else struct percpu_counter { long count; }; static inline void percpu_counter_init(struct percpu_counter *fbc) { fbc->count = 0; } static inline void percpu_counter_destroy(struct percpu_counter *fbc) { } static inline void percpu_counter_mod(struct percpu_counter *fbc, long amount) { preempt_disable(); fbc->count += amount; preempt_enable(); } static inline long percpu_counter_read(struct percpu_counter *fbc) { return fbc->count; } static inline long percpu_counter_read_positive(struct percpu_counter *fbc) { return fbc->count; } #endif /* CONFIG_SMP */ static inline void percpu_counter_inc(struct percpu_counter *fbc) { percpu_counter_mod(fbc, 1); } static inline void percpu_counter_dec(struct percpu_counter *fbc) { percpu_counter_mod(fbc, -1); } #endif /* _LINUX_PERCPU_COUNTER_H */ |