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Commit 6c9692e2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Rusty Russell
Browse files

module: Make the mod_tree stuff conditional on PERF_EVENTS || TRACING 



Andrew worried about the overhead on small systems; only use the fancy
code when either perf or tracing is enabled.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Requested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 93c2e105

include/linux/module.h

+3 −1
Original line number Diff line number Diff line
@@ -282,7 +282,7 @@ struct module { 
	 *

	 * Cacheline align here, such that:

	 *   module_init, module_core, init_size, core_size,

	 *   init_text_size, core_text_size and ltn_core.node[0]

	 *   init_text_size, core_text_size and mtn_core::{mod,node[0]}

	 * are on the same cacheline.

	 */

	void *module_init	____cacheline_aligned;
@@ -296,6 +296,7 @@ struct module { 
	/* The size of the executable code in each section.  */

	unsigned int init_text_size, core_text_size;



#ifdef CONFIG_MODULES_TREE_LOOKUP

	/*

	 * We want mtn_core::{mod,node[0]} to be in the same cacheline as the

	 * above entries such that a regular lookup will only touch one
@@ -303,6 +304,7 @@ struct module { 
	 */

	struct mod_tree_node	mtn_core;

	struct mod_tree_node	mtn_init;

#endif



	/* Size of RO sections of the module (text+rodata) */

	unsigned int init_ro_size, core_ro_size;

init/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -1989,6 +1989,10 @@ endchoice 


endif # MODULES



config MODULES_TREE_LOOKUP

	def_bool y

	depends on PERF_EVENTS || TRACING



config INIT_ALL_POSSIBLE

	bool

	help

kernel/module.c

+28 −2
Original line number Diff line number Diff line
@@ -102,6 +102,8 @@ DEFINE_MUTEX(module_mutex); 
EXPORT_SYMBOL_GPL(module_mutex);

static LIST_HEAD(modules);



#ifdef CONFIG_MODULES_TREE_LOOKUP



/*

 * Use a latched RB-tree for __module_address(); this allows us to use

 * RCU-sched lookups of the address from any context.
@@ -112,6 +114,10 @@ static LIST_HEAD(modules); 
 *

 * Because init ranges are short lived we mark them unlikely and have placed

 * them outside the critical cacheline in struct module.

 *

 * This is conditional on PERF_EVENTS || TRACING because those can really hit

 * __module_address() hard by doing a lot of stack unwinding; potentially from

 * NMI context.

 */



static __always_inline unsigned long __mod_tree_val(struct latch_tree_node *n)
@@ -192,7 +198,7 @@ static void mod_tree_remove(struct module *mod) 
	mod_tree_remove_init(mod);

}



static struct module *mod_tree_find(unsigned long addr)

static struct module *mod_find(unsigned long addr)

{

	struct latch_tree_node *ltn;
@@ -203,6 +209,26 @@ static struct module *mod_tree_find(unsigned long addr) 
	return container_of(ltn, struct mod_tree_node, node)->mod;

}



#else /* MODULES_TREE_LOOKUP */



static void mod_tree_insert(struct module *mod) { }

static void mod_tree_remove_init(struct module *mod) { }

static void mod_tree_remove(struct module *mod) { }



static struct module *mod_find(unsigned long addr)

{

	struct module *mod;



	list_for_each_entry_rcu(mod, &modules, list) {

		if (within_module(addr, mod))

			return mod;

	}



	return NULL;

}



#endif /* MODULES_TREE_LOOKUP */



#ifdef CONFIG_KGDB_KDB

struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */

#endif /* CONFIG_KGDB_KDB */
@@ -3966,7 +3992,7 @@ struct module *__module_address(unsigned long addr) 


	module_assert_mutex_or_preempt();



	mod = mod_tree_find(addr);

	mod = mod_find(addr);

	if (mod) {

		BUG_ON(!within_module(addr, mod));

		if (mod->state == MODULE_STATE_UNFORMED)