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Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu 

* 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu:
  rcu: Prevent RCU callbacks from executing before scheduler initialized
This commit is contained in:
Linus Torvalds 2011-07-15 09:54:34 -07:00
parent c64be78ffb b0d304172f
commit df8d6fe9ef
2 changed files with 36 additions and 5 deletions
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26
kernel/rcutree.c
View File

@ -84,9 +84,32 @@ DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
static struct rcu_state *rcu_state;
/*
* The rcu_scheduler_active variable transitions from zero to one just
* before the first task is spawned. So when this variable is zero, RCU
* can assume that there is but one task, allowing RCU to (for example)
* optimized synchronize_sched() to a simple barrier(). When this variable
* is one, RCU must actually do all the hard work required to detect real
* grace periods. This variable is also used to suppress boot-time false
* positives from lockdep-RCU error checking.
*/
int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
/*
* The rcu_scheduler_fully_active variable transitions from zero to one
* during the early_initcall() processing, which is after the scheduler
* is capable of creating new tasks. So RCU processing (for example,
* creating tasks for RCU priority boosting) must be delayed until after
* rcu_scheduler_fully_active transitions from zero to one. We also
* currently delay invocation of any RCU callbacks until after this point.
*
* It might later prove better for people registering RCU callbacks during
* early boot to take responsibility for these callbacks, but one step at
* a time.
*/
static int rcu_scheduler_fully_active __read_mostly;
#ifdef CONFIG_RCU_BOOST
/*
@ -98,7 +121,6 @@ DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
DEFINE_PER_CPU(char, rcu_cpu_has_work);
static char rcu_kthreads_spawnable;
#endif /* #ifdef CONFIG_RCU_BOOST */
@ -1467,6 +1489,8 @@ static void rcu_process_callbacks(struct softirq_action *unused)
*/
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
{
if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
return;
if (likely(!rsp->boost)) {
rcu_do_batch(rsp, rdp);
return;

15
kernel/rcutree_plugin.h
View File

@ -1532,7 +1532,7 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
struct sched_param sp;
struct task_struct *t;
if (!rcu_kthreads_spawnable ||
if (!rcu_scheduler_fully_active ||
per_cpu(rcu_cpu_kthread_task, cpu) != NULL)
return 0;
t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu);
@ -1639,7 +1639,7 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
struct sched_param sp;
struct task_struct *t;
if (!rcu_kthreads_spawnable ||
if (!rcu_scheduler_fully_active ||
rnp->qsmaskinit == 0)
return 0;
if (rnp->node_kthread_task == NULL) {
@ -1665,7 +1665,7 @@ static int __init rcu_spawn_kthreads(void)
int cpu;
struct rcu_node *rnp;
rcu_kthreads_spawnable = 1;
rcu_scheduler_fully_active = 1;
for_each_possible_cpu(cpu) {
per_cpu(rcu_cpu_has_work, cpu) = 0;
if (cpu_online(cpu))
@ -1687,7 +1687,7 @@ static void __cpuinit rcu_prepare_kthreads(int cpu)
struct rcu_node *rnp = rdp->mynode;
/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
if (rcu_kthreads_spawnable) {
if (rcu_scheduler_fully_active) {
(void)rcu_spawn_one_cpu_kthread(cpu);
if (rnp->node_kthread_task == NULL)
(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
@ -1726,6 +1726,13 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
{
}
static int __init rcu_scheduler_really_started(void)
{
rcu_scheduler_fully_active = 1;
return 0;
}
early_initcall(rcu_scheduler_really_started);
static void __cpuinit rcu_prepare_kthreads(int cpu)
{
}