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module: Use this_cpu_xx to dynamically allocate counters

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Use cpu ops to deal with the per cpu data instead of a local_t. Reduces memory
requirements, cache footprint and decreases cycle counts.

The this_cpu_xx operations are also used for !SMP mode. Otherwise we could
not drop the use of __module_ref_addr() which would make per cpu data handling
complicated. this_cpu_xx operations have their own fallback for !SMP.

V8-V9:
- Leave include asm/module.h since ringbuffer.c depends on it. Nothing else
  does though. Another patch will deal with that.
- Remove spurious free.

Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Christoph Lameter 2010-01-05 15:34:50 +09:00 • committed by Tejun Heo
parent 38b7827fcd
commit e1783a240f
2 changed files with 29 additions and 36 deletions
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36
include/linux/module.h
View file

@ -18,6 +18,7 @@
#include <linux/tracepoint.h>
#include <asm/local.h>
#include <linux/percpu.h>
#include <asm/module.h>
#include <trace/events/module.h>
@ -363,11 +364,9 @@ struct module
/* Destruction function. */
void (*exit)(void);
#ifdef CONFIG_SMP
char *refptr;
#else
local_t ref;
#endif
struct module_ref {
int count;
} *refptr;
#endif
#ifdef CONFIG_CONSTRUCTORS
@ -454,25 +453,16 @@ void __symbol_put(const char *symbol);
#define symbol_put(x) __symbol_put(MODULE_SYMBOL_PREFIX #x)
void symbol_put_addr(void *addr);
static inline local_t *__module_ref_addr(struct module *mod, int cpu)
{
#ifdef CONFIG_SMP
return (local_t *) (mod->refptr + per_cpu_offset(cpu));
#else
return &mod->ref;
#endif
}
/* Sometimes we know we already have a refcount, and it's easier not
to handle the error case (which only happens with rmmod --wait). */
static inline void __module_get(struct module *module)
{
if (module) {
unsigned int cpu = get_cpu();
local_inc(__module_ref_addr(module, cpu));
preempt_disable();
__this_cpu_inc(module->refptr->count);
trace_module_get(module, _THIS_IP_,
local_read(__module_ref_addr(module, cpu)));
put_cpu();
__this_cpu_read(module->refptr->count));
preempt_enable();
}
}
@ -481,15 +471,17 @@ static inline int try_module_get(struct module *module)
int ret = 1;
if (module) {
unsigned int cpu = get_cpu();
preempt_disable();
if (likely(module_is_live(module))) {
local_inc(__module_ref_addr(module, cpu));
__this_cpu_inc(module->refptr->count);
trace_module_get(module, _THIS_IP_,
local_read(__module_ref_addr(module, cpu)));
__this_cpu_read(module->refptr->count));
}
else
ret = 0;
put_cpu();
preempt_enable();
}
return ret;
}