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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-01-11 16:33:17 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-02-21 09:03:41 -0800
commit768dfffdffbfcc07d6927bdd642c714c0dd64c99 (patch)
tree3f559e37c0ff2ae59af963024c0d3595fa3d4b8e /kernel/rcutiny_plugin.h
parentafef20540f7cd1ea91bc1ac20be238389eee4003 (diff)
rcu: Prevent RCU callbacks from executing before scheduler initialized
This is a port of commit #b0d3041 from TREE_RCU to TREE_PREEMPT_RCU. Under some rare but real combinations of configuration parameters, RCU callbacks are posted during early boot that use kernel facilities that are not yet initialized. Therefore, when these callbacks are invoked, hard hangs and crashes ensue. This commit therefore prevents RCU callbacks from being invoked until after the scheduler is fully up and running, as in after multiple tasks have been spawned. It might well turn out that a better approach is to identify the specific RCU callbacks that are causing this problem, but that discussion will wait until such time as someone really needs an RCU callback to be invoked (as opposed to merely registered) during early boot. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutiny_plugin.h')
-rw-r--r--kernel/rcutiny_plugin.h15
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index b58a3200f0ff..95df60ebe363 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -914,7 +914,8 @@ static void rcu_preempt_process_callbacks(void)
static void invoke_rcu_callbacks(void)
{
have_rcu_kthread_work = 1;
- wake_up(&rcu_kthread_wq);
+ if (rcu_kthread_task != NULL)
+ wake_up(&rcu_kthread_wq);
}
#ifdef CONFIG_RCU_TRACE
@@ -975,12 +976,16 @@ early_initcall(rcu_spawn_kthreads);
#else /* #ifdef CONFIG_RCU_BOOST */
+/* Hold off callback invocation until early_initcall() time. */
+static int rcu_scheduler_fully_active __read_mostly;
+
/*
* Start up softirq processing of callbacks.
*/
void invoke_rcu_callbacks(void)
{
- raise_softirq(RCU_SOFTIRQ);
+ if (rcu_scheduler_fully_active)
+ raise_softirq(RCU_SOFTIRQ);
}
#ifdef CONFIG_RCU_TRACE
@@ -995,10 +1000,14 @@ static bool rcu_is_callbacks_kthread(void)
#endif /* #ifdef CONFIG_RCU_TRACE */
-void rcu_init(void)
+static int __init rcu_scheduler_really_started(void)
{
+ rcu_scheduler_fully_active = 1;
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+ raise_softirq(RCU_SOFTIRQ); /* Invoke any callbacks from early boot. */
+ return 0;
}
+early_initcall(rcu_scheduler_really_started);
#endif /* #else #ifdef CONFIG_RCU_BOOST */