cregit-Linux how code gets into the kernel

Release 4.9 lib/percpu_counter.c

Directory: lib
/*
 * Fast batching percpu counters.
 */

#include <linux/percpu_counter.h>
#include <linux/notifier.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/debugobjects.h>

#ifdef CONFIG_HOTPLUG_CPU
static LIST_HEAD(percpu_counters);
static DEFINE_SPINLOCK(percpu_counters_lock);
#endif

#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER


static struct debug_obj_descr percpu_counter_debug_descr;


static bool percpu_counter_fixup_free(void *addr, enum debug_obj_state state) { struct percpu_counter *fbc = addr; switch (state) { case ODEBUG_STATE_ACTIVE: percpu_counter_destroy(fbc); debug_object_free(fbc, &percpu_counter_debug_descr); return true; default: return false; } }

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static struct debug_obj_descr percpu_counter_debug_descr = { .name = "percpu_counter", .fixup_free = percpu_counter_fixup_free, };
static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) { debug_object_init(fbc, &percpu_counter_debug_descr); debug_object_activate(fbc, &percpu_counter_debug_descr); }

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static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) { debug_object_deactivate(fbc, &percpu_counter_debug_descr); debug_object_free(fbc, &percpu_counter_debug_descr); }

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#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) { }

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static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) { }

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#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
void percpu_counter_set(struct percpu_counter *fbc, s64 amount) { int cpu; unsigned long flags; raw_spin_lock_irqsave(&fbc->lock, flags); for_each_possible_cpu(cpu) { s32 *pcount = per_cpu_ptr(fbc->counters, cpu); *pcount = 0; } fbc->count = amount; raw_spin_unlock_irqrestore(&fbc->lock, flags); }

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EXPORT_SYMBOL(percpu_counter_set);
void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) { s64 count; preempt_disable(); count = __this_cpu_read(*fbc->counters) + amount; if (count >= batch || count <= -batch) { unsigned long flags; raw_spin_lock_irqsave(&fbc->lock, flags); fbc->count += count; __this_cpu_sub(*fbc->counters, count - amount); raw_spin_unlock_irqrestore(&fbc->lock, flags); } else { this_cpu_add(*fbc->counters, amount); } preempt_enable(); }

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EXPORT_SYMBOL(__percpu_counter_add); /* * Add up all the per-cpu counts, return the result. This is a more accurate * but much slower version of percpu_counter_read_positive() */
s64 __percpu_counter_sum(struct percpu_counter *fbc) { s64 ret; int cpu; unsigned long flags; raw_spin_lock_irqsave(&fbc->lock, flags); ret = fbc->count; for_each_online_cpu(cpu) { s32 *pcount = per_cpu_ptr(fbc->counters, cpu); ret += *pcount; } raw_spin_unlock_irqrestore(&fbc->lock, flags); return ret; }

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EXPORT_SYMBOL(__percpu_counter_sum);
int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp, struct lock_class_key *key) { unsigned long flags __maybe_unused; raw_spin_lock_init(&fbc->lock); lockdep_set_class(&fbc->lock, key); fbc->count = amount; fbc->counters = alloc_percpu_gfp(s32, gfp); if (!fbc->counters) return -ENOMEM; debug_percpu_counter_activate(fbc); #ifdef CONFIG_HOTPLUG_CPU INIT_LIST_HEAD(&fbc->list); spin_lock_irqsave(&percpu_counters_lock, flags); list_add(&fbc->list, &percpu_counters); spin_unlock_irqrestore(&percpu_counters_lock, flags); #endif return 0; }

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EXPORT_SYMBOL(__percpu_counter_init);
void percpu_counter_destroy(struct percpu_counter *fbc) { unsigned long flags __maybe_unused; if (!fbc->counters) return; debug_percpu_counter_deactivate(fbc); #ifdef CONFIG_HOTPLUG_CPU spin_lock_irqsave(&percpu_counters_lock, flags); list_del(&fbc->list); spin_unlock_irqrestore(&percpu_counters_lock, flags); #endif free_percpu(fbc->counters); fbc->counters = NULL; }

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EXPORT_SYMBOL(percpu_counter_destroy); int percpu_counter_batch __read_mostly = 32; EXPORT_SYMBOL(percpu_counter_batch);
static void compute_batch_value(void) { int nr = num_online_cpus(); percpu_counter_batch = max(32, nr*2); }

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static int percpu_counter_hotcpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu) { #ifdef CONFIG_HOTPLUG_CPU unsigned int cpu; struct percpu_counter *fbc; compute_batch_value(); if (action != CPU_DEAD && action != CPU_DEAD_FROZEN) return NOTIFY_OK; cpu = (unsigned long)hcpu; spin_lock_irq(&percpu_counters_lock); list_for_each_entry(fbc, &percpu_counters, list) { s32 *pcount; unsigned long flags; raw_spin_lock_irqsave(&fbc->lock, flags); pcount = per_cpu_ptr(fbc->counters, cpu); fbc->count += *pcount; *pcount = 0; raw_spin_unlock_irqrestore(&fbc->lock, flags); } spin_unlock_irq(&percpu_counters_lock); #endif return NOTIFY_OK; }

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/* * Compare counter against given value. * Return 1 if greater, 0 if equal and -1 if less */
int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch) { s64 count; count = percpu_counter_read(fbc); /* Check to see if rough count will be sufficient for comparison */ if (abs(count - rhs) > (batch * num_online_cpus())) { if (count > rhs) return 1; else return -1; } /* Need to use precise count */ count = percpu_counter_sum(fbc); if (count > rhs) return 1; else if (count < rhs) return -1; else return 0; }

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EXPORT_SYMBOL(__percpu_counter_compare);
static int __init percpu_counter_startup(void) { compute_batch_value(); hotcpu_notifier(percpu_counter_hotcpu_callback, 0); return 0; }

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module_init(percpu_counter_startup);

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peter zijlstrapeter zijlstra11612.15%620.00%
tim chentim chen919.53%13.33%
eric dumazeteric dumazet606.28%26.67%
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christoph lameterchristoph lameter161.68%26.67%
lei minglei ming101.05%13.33%
masanori itohmasanori itoh80.84%13.33%
gautham r shenoygautham r shenoy80.84%13.33%
dave chinnerdave chinner60.63%13.33%
glauber costaglauber costa50.52%13.33%
jens axboejens axboe40.42%13.33%
changbin duchangbin du30.31%13.33%
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thomas gleixnerthomas gleixner30.31%13.33%
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Directory: lib