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Commit 0286b5ea authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Rusty Russell
Browse files

lib/bug: Use RCU list ops for module_bug_list 



Actually since module_bug_list should be used in BUG context,
we may not need this. But for someone who want to use this
from normal context, this makes module_bug_list an RCU list.

Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 461e34ae

kernel/module.c

+3 −2
Original line number Diff line number Diff line
@@ -1850,9 +1850,10 @@ static void free_module(struct module *mod) 
	mutex_lock(&module_mutex);

	/* Unlink carefully: kallsyms could be walking list. */

	list_del_rcu(&mod->list);

	/* Wait for RCU synchronizing before releasing mod->list. */

	synchronize_rcu();

	/* Remove this module from bug list, this uses list_del_rcu */

	module_bug_cleanup(mod);

	/* Wait for RCU synchronizing before releasing mod->list and buglist. */

	synchronize_rcu();

	mutex_unlock(&module_mutex);



	/* This may be NULL, but that's OK */

lib/bug.c

+14 −6
Original line number Diff line number Diff line
@@ -64,16 +64,22 @@ static LIST_HEAD(module_bug_list); 
static const struct bug_entry *module_find_bug(unsigned long bugaddr)

{

	struct module *mod;

	const struct bug_entry *bug = NULL;



	list_for_each_entry(mod, &module_bug_list, bug_list) {

		const struct bug_entry *bug = mod->bug_table;

	rcu_read_lock();

	list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {

		unsigned i;



		bug = mod->bug_table;

		for (i = 0; i < mod->num_bugs; ++i, ++bug)

			if (bugaddr == bug_addr(bug))

				return bug;

				goto out;

	}

	return NULL;

	bug = NULL;

out:

	rcu_read_unlock();



	return bug;

}



void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
@@ -99,13 +105,15 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 
	 * Strictly speaking this should have a spinlock to protect against

	 * traversals, but since we only traverse on BUG()s, a spinlock

	 * could potentially lead to deadlock and thus be counter-productive.

	 * Thus, this uses RCU to safely manipulate the bug list, since BUG

	 * must run in non-interruptive state.

	 */

	list_add(&mod->bug_list, &module_bug_list);

	list_add_rcu(&mod->bug_list, &module_bug_list);

}



void module_bug_cleanup(struct module *mod)

{

	list_del(&mod->bug_list);

	list_del_rcu(&mod->bug_list);

}



#else