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Commit e1783a24 authored by Christoph Lameter's avatar Christoph Lameter Committed by Tejun Heo
Browse files

module: Use this_cpu_xx to dynamically allocate counters 



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: default avatarChristoph Lameter <cl@linux-foundation.org>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 38b7827f

include/linux/module.h

+14 −22
Original line number Diff line number Diff line
@@ -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;

}

kernel/module.c

+15 −14
Original line number Diff line number Diff line
@@ -474,9 +474,10 @@ static void module_unload_init(struct module *mod) 


	INIT_LIST_HEAD(&mod->modules_which_use_me);

	for_each_possible_cpu(cpu)

		local_set(__module_ref_addr(mod, cpu), 0);

		per_cpu_ptr(mod->refptr, cpu)->count = 0;



	/* Hold reference count during initialization. */

	local_set(__module_ref_addr(mod, raw_smp_processor_id()), 1);

	__this_cpu_write(mod->refptr->count, 1);

	/* Backwards compatibility macros put refcount during init. */

	mod->waiter = current;

}
@@ -619,7 +620,7 @@ unsigned int module_refcount(struct module *mod) 
	int cpu;



	for_each_possible_cpu(cpu)

		total += local_read(__module_ref_addr(mod, cpu));

		total += per_cpu_ptr(mod->refptr, cpu)->count;

	return total;

}

EXPORT_SYMBOL(module_refcount);
@@ -796,14 +797,15 @@ static struct module_attribute refcnt = { 
void module_put(struct module *module)

{

	if (module) {

		unsigned int cpu = get_cpu();

		local_dec(__module_ref_addr(module, cpu));

		preempt_disable();

		__this_cpu_dec(module->refptr->count);



		trace_module_put(module, _RET_IP_,

				 local_read(__module_ref_addr(module, cpu)));

				 __this_cpu_read(module->refptr->count));

		/* Maybe they're waiting for us to drop reference? */

		if (unlikely(!module_is_live(module)))

			wake_up_process(module->waiter);

		put_cpu();

		preempt_enable();

	}

}

EXPORT_SYMBOL(module_put);
@@ -1394,9 +1396,9 @@ static void free_module(struct module *mod) 
	kfree(mod->args);

	if (mod->percpu)

		percpu_modfree(mod->percpu);

#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)

#if defined(CONFIG_MODULE_UNLOAD)

	if (mod->refptr)

		percpu_modfree(mod->refptr);

		free_percpu(mod->refptr);

#endif

	/* Free lock-classes: */

	lockdep_free_key_range(mod->module_core, mod->core_size);
@@ -2159,9 +2161,8 @@ static noinline struct module *load_module(void __user *umod, 
	mod = (void *)sechdrs[modindex].sh_addr;

	kmemleak_load_module(mod, hdr, sechdrs, secstrings);



#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)

	mod->refptr = percpu_modalloc(sizeof(local_t), __alignof__(local_t),

				      mod->name);

#if defined(CONFIG_MODULE_UNLOAD)

	mod->refptr = alloc_percpu(struct module_ref);

	if (!mod->refptr) {

		err = -ENOMEM;

		goto free_init;
@@ -2393,8 +2394,8 @@ static noinline struct module *load_module(void __user *umod, 
	kobject_put(&mod->mkobj.kobj);

 free_unload:

	module_unload_free(mod);

#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)

	percpu_modfree(mod->refptr);

#if defined(CONFIG_MODULE_UNLOAD)

	free_percpu(mod->refptr);

 free_init:

#endif

	module_free(mod, mod->module_init);