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SubjectRe: [RFC][PATCH] tracing/module: Move tracepoint out of module.h
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Le mercredi 01 février 2012 à 17:18 +1030, Rusty Russell a écrit :

>
> +void __module_get(struct module *module)
> +{
> + if (module) {
> + preempt_disable();
> + __this_cpu_inc(module->refptr->incs);
> + trace_module_get(module, _RET_IP_);
> + preempt_enable();
> + }
> +}
> +EXPORT_SYMBOL(__module_get);
> +

Hi Rusty

I am wondering why preempt_disable()/preempt_enable() is needed in this
code.

this_cpu_inc(module->refptr->incs) is preempt safe...



diff --git a/kernel/module.c b/kernel/module.c
index 78ac6ec..7dc88b3 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -907,10 +907,8 @@ static struct module_attribute modinfo_refcnt =
void __module_get(struct module *module)
{
if (module) {
- preempt_disable();
- __this_cpu_inc(module->refptr->incs);
+ this_cpu_inc(module->refptr->incs);
trace_module_get(module, _RET_IP_);
- preempt_enable();
}
}
EXPORT_SYMBOL(__module_get);
@@ -920,15 +918,11 @@ bool try_module_get(struct module *module)
bool ret = true;

if (module) {
- preempt_disable();
-
if (likely(module_is_live(module))) {
- __this_cpu_inc(module->refptr->incs);
+ this_cpu_inc(module->refptr->incs);
trace_module_get(module, _RET_IP_);
} else
ret = false;
-
- preempt_enable();
}
return ret;
}
@@ -937,15 +931,13 @@ EXPORT_SYMBOL(try_module_get);
void module_put(struct module *module)
{
if (module) {
- preempt_disable();
smp_wmb(); /* see comment in module_refcount */
- __this_cpu_inc(module->refptr->decs);
+ this_cpu_inc(module->refptr->decs);

trace_module_put(module, _RET_IP_);
/* Maybe they're waiting for us to drop reference? */
if (unlikely(!module_is_live(module)))
wake_up_process(module->waiter);
- preempt_enable();
}
}
EXPORT_SYMBOL(module_put);

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