Re: [PATCH tip/core/rcu 24/41] modules: Replace synchronize_sched() and call_rcu_sched()

Jessica Yu
2018-11-12T12:49:01Z

+++ Paul E. McKenney [11/11/18 11:43 -0800]:
>Now that synchronize_rcu() waits for preempt-disable regions of code
>as well as RCU read-side critical sections, synchronize_sched() can
>be replaced by synchronize_rcu(). Similarly, call_rcu_sched() can be
>replaced by call_rcu(). This commit therefore makes these changes.
>
>Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
>Cc: Jessica Yu <jeyu@kernel.org>

Acked-by: Jessica Yu <jeyu@kernel.org>

Thanks!

>---
> kernel/module.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 49a405891587..99b46c32d579 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -2159,7 +2159,7 @@ static void free_module(struct module *mod)
> /* Remove this module from bug list, this uses list_del_rcu */
> module_bug_cleanup(mod);
> /* Wait for RCU-sched synchronizing before releasing mod->list and buglist. */
>- synchronize_sched();
>+ synchronize_rcu();
> mutex_unlock(&module_mutex);
>
> /* This may be empty, but that's OK */
>@@ -3507,15 +3507,15 @@ static noinline int do_init_module(struct module *mod)
> /*
> * We want to free module_init, but be aware that kallsyms may be
> * walking this with preempt disabled. In all the failure paths, we
>- * call synchronize_sched(), but we don't want to slow down the success
>+ * call synchronize_rcu(), but we don't want to slow down the success
> * path, so use actual RCU here.
> * Note that module_alloc() on most architectures creates W+X page
> * mappings which won't be cleaned up until do_free_init() runs. Any
> * code such as mark_rodata_ro() which depends on those mappings to
> * be cleaned up needs to sync with the queued work - ie
>- * rcu_barrier_sched()
>+ * rcu_barrier()
> */
>- call_rcu_sched(&freeinit->rcu, do_free_init);
>+ call_rcu(&freeinit->rcu, do_free_init);
> mutex_unlock(&module_mutex);
> wake_up_all(&module_wq);
>
>@@ -3526,7 +3526,7 @@ static noinline int do_init_module(struct module *mod)
> fail:
> /* Try to protect us from buggy refcounters. */
> mod->state = MODULE_STATE_GOING;
>- synchronize_sched();
>+ synchronize_rcu();
> module_put(mod);
> blocking_notifier_call_chain(&module_notify_list,
> MODULE_STATE_GOING, mod);
>@@ -3819,7 +3819,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
> ddebug_cleanup:
> ftrace_release_mod(mod);
> dynamic_debug_remove(mod, info->debug);
>- synchronize_sched();
>+ synchronize_rcu();
> kfree(mod->args);
> free_arch_cleanup:
> module_arch_cleanup(mod);
>@@ -3834,7 +3834,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
> mod_tree_remove(mod);
> wake_up_all(&module_wq);
> /* Wait for RCU-sched synchronizing before releasing mod->list. */
>- synchronize_sched();
>+ synchronize_rcu();
> mutex_unlock(&module_mutex);
> free_module:
> /* Free lock-classes; relies on the preceding sync_rcu() */
>--
>2.17.1
>