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Commit 218ce735 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Revert "module: drop the lock while waiting for module to complete initialization." 



This reverts commit 480b02df, since
Rafael reports that it causes occasional kernel paging request faults in
load_module().

Dropping the module lock and re-taking it deep in the call-chain is
definitely not the right thing to do.  That just turns the mutex from a
lock into a "random non-locking data structure" that doesn't actually
protect what it's supposed to protect.

Requested-and-tested-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Brandon Philips <brandon@ifup.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ec96e2fe

kernel/module.c

+22 −37
Original line number Diff line number Diff line
@@ -563,26 +563,33 @@ int use_module(struct module *a, struct module *b) 
	struct module_use *use;

	int no_warn, err;



	if (b == NULL || already_uses(a, b))

		return 0;

	if (b == NULL || already_uses(a, b)) return 1;



	/* If we're interrupted or time out, we fail. */

	err = strong_try_module_get(b);

	if (wait_event_interruptible_timeout(

		    module_wq, (err = strong_try_module_get(b)) != -EBUSY,

		    30 * HZ) <= 0) {

		printk("%s: gave up waiting for init of module %s.\n",

		       a->name, b->name);

		return 0;

	}



	/* If strong_try_module_get() returned a different error, we fail. */

	if (err)

		return err;

		return 0;



	DEBUGP("Allocating new usage for %s.\n", a->name);

	use = kmalloc(sizeof(*use), GFP_ATOMIC);

	if (!use) {

		printk("%s: out of memory loading\n", a->name);

		module_put(b);

		return -ENOMEM;

		return 0;

	}



	use->module_which_uses = a;

	list_add(&use->list, &b->modules_which_use_me);

	no_warn = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);

	return 0;

	return 1;

}

EXPORT_SYMBOL_GPL(use_module);
@@ -875,7 +882,7 @@ static inline void module_unload_free(struct module *mod) 


int use_module(struct module *a, struct module *b)

{

	return strong_try_module_get(b);

	return strong_try_module_get(b) == 0;

}

EXPORT_SYMBOL_GPL(use_module);
@@ -1046,39 +1053,17 @@ static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs, 
	struct module *owner;

	const struct kernel_symbol *sym;

	const unsigned long *crc;

	DEFINE_WAIT(wait);

	int err;

	long timeleft = 30 * HZ;



again:

	sym = find_symbol(name, &owner, &crc,

			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);

	if (!sym)

		return NULL;



	if (!check_version(sechdrs, versindex, name, mod, crc, owner))

		return NULL;



	prepare_to_wait(&module_wq, &wait, TASK_INTERRUPTIBLE);

	err = use_module(mod, owner);

	if (likely(!err) || err != -EBUSY || signal_pending(current)) {

		finish_wait(&module_wq, &wait);

		return err ? NULL : sym;

	/* use_module can fail due to OOM,

	   or module initialization or unloading */

	if (sym) {

		if (!check_version(sechdrs, versindex, name, mod, crc, owner)

		    || !use_module(mod, owner))

			sym = NULL;

	}



	/* Module is still loading.  Drop lock and wait. */

	mutex_unlock(&module_mutex);

	timeleft = schedule_timeout(timeleft);

	mutex_lock(&module_mutex);

	finish_wait(&module_wq, &wait);



	/* Module might be gone entirely, or replaced.  Re-lookup. */

	if (timeleft)

		goto again;



	printk(KERN_WARNING "%s: gave up waiting for init of module %s.\n",

	       mod->name, owner->name);

	return NULL;

	return sym;

}



/*