Re: [PATCH 04/13] module: use RCU to synchronize find_module
From: Miroslav Benes <mbenes@suse.cz>
Date: 2021-01-29 15:30:52
On Thu, 28 Jan 2021, Christoph Hellwig wrote:
Allow for a RCU-sched critical section around find_module, following the lower level find_module_all helper, and switch the two callers outside of module.c to use such a RCU-sched critical section instead of module_mutex.
That's a nice idea.
quoted hunk ↗ jump to hunk
@@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object *obj) if (!klp_is_module(obj)) return; - mutex_lock(&module_mutex); + rcu_read_lock_sched(); /* * We do not want to block removal of patched modules and therefore * we do not take a reference here. The patches are removed by@@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj) if (mod && mod->klp_alive)
RCU always baffles me a bit, so I'll ask. Don't we need rcu_dereference_sched() here? "mod" comes from a RCU-protected list, so I wonder.
obj->mod = mod; - mutex_unlock(&module_mutex); + rcu_read_unlock_sched(); }
Thanks Miroslav