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Subject[patch v2 3/5] percpu_counter: use lglock to protect percpu data
uses lglock to protect percpu data. This is a preparation to remove
percpu_counter global lock.
This will slow __percpu_counter_sum, but this one is supposed not to be called
frequently, so doesn't matter.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
---
include/linux/percpu_counter.h | 9 ++++++---
lib/percpu_counter.c | 15 ++++++++++++++-
2 files changed, 20 insertions(+), 4 deletions(-)
Index: linux/include/linux/percpu_counter.h
===================================================================
--- linux.orig/include/linux/percpu_counter.h 2011-05-10 16:23:01.000000000 +0800
+++ linux/include/linux/percpu_counter.h 2011-05-11 09:28:55.000000000 +0800
@@ -12,6 +12,7 @@
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>
+#include <linux/lglock.h>

#ifdef CONFIG_SMP

@@ -22,18 +23,20 @@ struct percpu_counter {
struct list_head list; /* All percpu_counters are on a list */
#endif
s32 __percpu *counters;
+ struct lglock lglock;
};

extern int percpu_counter_batch;

int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
- struct lock_class_key *key);
+ struct lock_class_key *key, const char *name,
+ struct lock_class_key *key2);

#define percpu_counter_init(fbc, value) \
({ \
- static struct lock_class_key __key; \
+ static struct lock_class_key __key, __key2; \
\
- __percpu_counter_init(fbc, value, &__key); \
+ __percpu_counter_init(fbc, value, &__key, #fbc, &__key2);\
})

void percpu_counter_destroy(struct percpu_counter *fbc);
Index: linux/lib/percpu_counter.c
===================================================================
--- linux.orig/lib/percpu_counter.c 2011-05-10 16:10:54.000000000 +0800
+++ linux/lib/percpu_counter.c 2011-05-11 09:28:55.000000000 +0800
@@ -77,8 +77,10 @@ void __percpu_counter_add(struct percpu_
count = __this_cpu_read(*fbc->counters) + amount;
if (count >= batch || count <= -batch) {
spin_lock(&fbc->lock);
+ lg_local_lock(fbc->lglock);
fbc->count += count;
__this_cpu_write(*fbc->counters, 0);
+ lg_local_unlock(fbc->lglock);
spin_unlock(&fbc->lock);
} else {
__this_cpu_write(*fbc->counters, count);
@@ -97,18 +99,21 @@ s64 __percpu_counter_sum(struct percpu_c
int cpu;

spin_lock(&fbc->lock);
+ lg_global_lock_online(fbc->lglock);
ret = fbc->count;
for_each_online_cpu(cpu) {
s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
ret += *pcount;
}
+ lg_global_unlock_online(fbc->lglock);
spin_unlock(&fbc->lock);
return ret;
}
EXPORT_SYMBOL(__percpu_counter_sum);

int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
- struct lock_class_key *key)
+ struct lock_class_key *key, const char *name,
+ struct lock_class_key *key2)
{
spin_lock_init(&fbc->lock);
lockdep_set_class(&fbc->lock, key);
@@ -116,6 +121,11 @@ int __percpu_counter_init(struct percpu_
fbc->counters = alloc_percpu(s32);
if (!fbc->counters)
return -ENOMEM;
+ if (lglock_alloc(&fbc->lglock)) {
+ free_percpu(fbc->counters);
+ return -ENOMEM;
+ }
+ __lglock_init(&fbc->lglock, name, key2);

debug_percpu_counter_activate(fbc);

@@ -143,6 +153,7 @@ void percpu_counter_destroy(struct percp
#endif
free_percpu(fbc->counters);
fbc->counters = NULL;
+ lglock_free(&fbc->lglock);
}
EXPORT_SYMBOL(percpu_counter_destroy);

@@ -174,9 +185,11 @@ static int __cpuinit percpu_counter_hotc
unsigned long flags;

spin_lock_irqsave(&fbc->lock, flags);
+ lg_local_lock_cpu(fbc->lglock, cpu);
pcount = per_cpu_ptr(fbc->counters, cpu);
fbc->count += *pcount;
*pcount = 0;
+ lg_local_unlock_cpu(fbc->lglock, cpu);
spin_unlock_irqrestore(&fbc->lock, flags);
}
mutex_unlock(&percpu_counters_lock);


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