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

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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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Peter Zijlstra 2015-05-27 11:09:37 +09:30 committed by Rusty Russell
parent 93c2e105f6
commit 6c9692e2d6
3 changed files with 35 additions and 3 deletions
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4
include/linux/module.h
View File

@ -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;

4
init/Kconfig
View File

@ -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

30
kernel/module.c
View File

@ -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)