[PATCH] atomic: fix a typo in atomic_long_xchg()

Eric Dumazet
2008-12-07T22:25:20Z

Andrew Morton a écrit :
> We can do lots of things in 2.6.29. Including just making ->counters
> an array of atomic_t.

I was playing with this idea this week (but using atomic_long_t),
and this is why I bother you with all this stuff : cleanup patches
before work for 2.6.29

My idea was using atomic_long_t so that 64bit arches dont need
a spinlock any more, and new percpu_lcounter would be ok for
counters that dont need s64 but a plain long (nr_files, network
counters...)

struct percpu_lcounter {
atomic_long_t count;
#ifdef CONFIG_SMP
#ifdef CONFIG_HOTPLUG_CPU
struct list_head list; /* All percpu_counters are on a list */
#endif
atomic_long_t *counters;
#endif
};

void __percpu_lcounter_add(struct percpu_lcounter *fbc, long amount, s32 batch)
{
long count;
atomic_long_t *pcount;

pcount = per_cpu_ptr(fbc->counters, get_cpu());
count = atomic_long_add_return(amount, pcount);
if (unlikely(count >= batch || count <= -batch)) {
atomic_long_add(count, &fbc->count);
atomic_long_sub(count, pcount);
}
put_cpu();
}

long percpu_lcounter_sum(struct percpu_lcounter *fbc)
{
long accumulator = 0, val;
int cpu;

for_each_online_cpu(cpu) {
atomic_long_t *pcount = per_cpu_ptr(fbc->counters, cpu);

val = atomic_long_xchg(pcount, 0);
accumulator += val;
}
return atomic_long_add_return(accumulator, &fbc->count);
}

Then I found the following typo :

[PATCH] atomic: fix a typo in atomic_long_xchg()

atomic_long_xchg() not correctly defined for 32bit arches.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
---
diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
index 4ec0a29..7abdaa9 100644
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -251,7 +251,7 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u)
#define atomic_long_cmpxchg(l, old, new) \
(atomic_cmpxchg((atomic_t *)(l), (old), (new)))
#define atomic_long_xchg(v, new) \
- (atomic_xchg((atomic_t *)(l), (new)))
+ (atomic_xchg((atomic_t *)(v), (new)))

#endif /* BITS_PER_LONG == 64 */