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module: make locking more fine-grained.

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Kay Sievers <kay.sievers@vrfy.org> reports that we still have some
contention over module loading which is slowing boot.

Linus also disliked a previous "drop lock and regrab" patch to fix the
bne2 "gave up waiting for init of module libcrc32c" message.

This is more ambitious: we only grab the lock where we need it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Brandon Philips <brandon@ifup.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rusty Russell 2010-06-05 11:17:36 -06:00
parent 6407ebb271
commit 75676500f8
1 changed files with 42 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
kernel/module.c
View File

@ -72,7 +72,11 @@
/* If this is set, the section belongs in the init part of the module */
#define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
/* List of modules, protected by module_mutex or preempt_disable
/*
* Mutex protects:
* 1) List of modules (also safely readable with preempt_disable),
* 2) module_use links,
* 3) module_addr_min/module_addr_max.
* (delete uses stop_machine/add uses RCU list operations). */
DEFINE_MUTEX(module_mutex);
EXPORT_SYMBOL_GPL(module_mutex);
@ -90,7 +94,8 @@ static DECLARE_WAIT_QUEUE_HEAD(module_wq);
static BLOCKING_NOTIFIER_HEAD(module_notify_list);
/* Bounds of module allocation, for speeding __module_address */
/* Bounds of module allocation, for speeding __module_address.
* Protected by module_mutex. */
static unsigned long module_addr_min = -1UL, module_addr_max = 0;
int register_module_notifier(struct notifier_block * nb)
@ -329,7 +334,7 @@ static bool find_symbol_in_section(const struct symsearch *syms,
}
/* Find a symbol and return it, along with, (optional) crc and
* (optional) module which owns it */
* (optional) module which owns it. Needs preempt disabled or module_mutex. */
const struct kernel_symbol *find_symbol(const char *name,
struct module **owner,
const unsigned long **crc,
@ -576,7 +581,7 @@ static int add_module_usage(struct module *a, struct module *b)
return 0;
}
/* Module a uses b */
/* Module a uses b: caller needs module_mutex() */
int use_module(struct module *a, struct module *b)
{
int err;
@ -610,6 +615,7 @@ static void module_unload_free(struct module *mod)
{
struct module_use *use, *tmp;
mutex_lock(&module_mutex);
list_for_each_entry_safe(use, tmp, &mod->target_list, target_list) {
struct module *i = use->target;
DEBUGP("%s unusing %s\n", mod->name, i->name);
@ -618,6 +624,7 @@ static void module_unload_free(struct module *mod)
list_del(&use->target_list);
kfree(use);
}
mutex_unlock(&module_mutex);
}
#ifdef CONFIG_MODULE_FORCE_UNLOAD
@ -784,13 +791,14 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
async_synchronize_full();
mutex_lock(&module_mutex);
/* Store the name of the last unloaded module for diagnostic purposes */
strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
ddebug_remove_module(mod->name);
free_module(mod);
out:
free_module(mod);
return 0;
out:
mutex_unlock(&module_mutex);
return ret;
}
@ -1006,6 +1014,8 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
{
const unsigned long *crc;
/* Since this should be found in kernel (which can't be removed),
* no locking is necessary. */
if (!find_symbol(MODULE_SYMBOL_PREFIX "module_layout", NULL,
&crc, true, false))
BUG();
@ -1048,8 +1058,7 @@ static inline int same_magic(const char *amagic, const char *bmagic,
}
#endif /* CONFIG_MODVERSIONS */
/* Resolve a symbol for this module. I.e. if we find one, record usage.
Must be holding module_mutex. */
/* Resolve a symbol for this module. I.e. if we find one, record usage. */
static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
unsigned int versindex,
const char *name,
@ -1059,6 +1068,7 @@ static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
const struct kernel_symbol *sym;
const unsigned long *crc;
mutex_lock(&module_mutex);
sym = find_symbol(name, &owner, &crc,
!(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
/* use_module can fail due to OOM,
@ -1068,6 +1078,7 @@ static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
|| !use_module(mod, owner))
sym = NULL;
}
mutex_unlock(&module_mutex);
return sym;
}
@ -1306,10 +1317,12 @@ static void add_usage_links(struct module *mod)
struct module_use *use;
int nowarn;
mutex_lock(&module_mutex);
list_for_each_entry(use, &mod->target_list, target_list) {
nowarn = sysfs_create_link(use->target->holders_dir,
&mod->mkobj.kobj, mod->name);
}
mutex_unlock(&module_mutex);
#endif
}
@ -1318,8 +1331,10 @@ static void del_usage_links(struct module *mod)
#ifdef CONFIG_MODULE_UNLOAD
struct module_use *use;
mutex_lock(&module_mutex);
list_for_each_entry(use, &mod->target_list, target_list)
sysfs_remove_link(use->target->holders_dir, mod->name);
mutex_unlock(&module_mutex);
#endif
}
@ -1497,13 +1512,15 @@ static int __unlink_module(void *_mod)
return 0;
}
/* Free a module, remove from lists, etc (must hold module_mutex). */
/* Free a module, remove from lists, etc. */
static void free_module(struct module *mod)
{
trace_module_free(mod);
/* Delete from various lists */
mutex_lock(&module_mutex);
stop_machine(__unlink_module, mod, NULL);
mutex_unlock(&module_mutex);
remove_notes_attrs(mod);
remove_sect_attrs(mod);
mod_kobject_remove(mod);
@ -1575,7 +1592,14 @@ static int verify_export_symbols(struct module *mod)
for (i = 0; i < ARRAY_SIZE(arr); i++) {
for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
if (find_symbol(s->name, &owner, NULL, true, false)) {
const struct kernel_symbol *sym;
/* Stopping preemption makes find_symbol safe. */
preempt_disable();
sym = find_symbol(s->name, &owner, NULL, true, false);
preempt_enable();
if (sym) {
printk(KERN_ERR
"%s: exports duplicate symbol %s"
" (owned by %s)\n",
@ -2021,11 +2045,13 @@ static void *module_alloc_update_bounds(unsigned long size)
void *ret = module_alloc(size);
if (ret) {
mutex_lock(&module_mutex);
/* Update module bounds. */
if ((unsigned long)ret < module_addr_min)
module_addr_min = (unsigned long)ret;
if ((unsigned long)ret + size > module_addr_max)
module_addr_max = (unsigned long)ret + size;
mutex_unlock(&module_mutex);
}
return ret;
}
@ -2482,7 +2508,9 @@ static noinline struct module *load_module(void __user *umod,
* function to insert in a way safe to concurrent readers.
* The mutex protects against concurrent writers.
*/
mutex_lock(&module_mutex);
list_add_rcu(&mod->list, &modules);
mutex_unlock(&module_mutex);
err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL);
if (err < 0)
@ -2504,8 +2532,10 @@ static noinline struct module *load_module(void __user *umod,
return mod;
unlink:
mutex_lock(&module_mutex);
/* Unlink carefully: kallsyms could be walking list. */
list_del_rcu(&mod->list);
mutex_unlock(&module_mutex);
synchronize_sched();
module_arch_cleanup(mod);
cleanup:
@ -2556,19 +2586,10 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
if (!capable(CAP_SYS_MODULE) || modules_disabled)
return -EPERM;
/* Only one module load at a time, please */
if (mutex_lock_interruptible(&module_mutex) != 0)
return -EINTR;
/* Do all the hard work */
mod = load_module(umod, len, uargs);
if (IS_ERR(mod)) {
mutex_unlock(&module_mutex);
if (IS_ERR(mod))
return PTR_ERR(mod);
}
/* Drop lock so they can recurse */
mutex_unlock(&module_mutex);
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_COMING, mod);
@ -2585,9 +2606,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
module_put(mod);
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
mutex_lock(&module_mutex);
free_module(mod);
mutex_unlock(&module_mutex);
wake_up(&module_wq);
return ret;
}