forked from Minki/linux
rcu: Move RCU_BOOST #ifdefs to header file
The commit "use softirq instead of kthreads except when RCU_BOOST=y" just applied #ifdef in place. This commit is a cleanup that moves the newly #ifdef'ed code to the header file kernel/rcutree_plugin.h. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
Paul E. McKenney
parent
a46e0899ee
commit
f8b7fc6b51
383
kernel/rcutree.c
383
kernel/rcutree.c
@ -1093,16 +1093,8 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
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int need_report = 0;
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struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
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struct rcu_node *rnp;
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#ifdef CONFIG_RCU_BOOST
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struct task_struct *t;
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/* Stop the CPU's kthread. */
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t = per_cpu(rcu_cpu_kthread_task, cpu);
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if (t != NULL) {
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per_cpu(rcu_cpu_kthread_task, cpu) = NULL;
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kthread_stop(t);
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}
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#endif /* #ifdef CONFIG_RCU_BOOST */
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rcu_stop_cpu_kthread(cpu);
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/* Exclude any attempts to start a new grace period. */
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raw_spin_lock_irqsave(&rsp->onofflock, flags);
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@ -1453,17 +1445,6 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
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invoke_rcu_callbacks(rsp, rdp);
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}
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#ifdef CONFIG_RCU_BOOST
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static void rcu_kthread_do_work(void)
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{
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rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data));
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rcu_do_batch(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
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rcu_preempt_do_callbacks();
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}
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#endif /* #ifdef CONFIG_RCU_BOOST */
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/*
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* Do softirq processing for the current CPU.
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*/
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@ -1498,345 +1479,6 @@ static void invoke_rcu_core(void)
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raise_softirq(RCU_SOFTIRQ);
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}
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#ifdef CONFIG_RCU_BOOST
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/*
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* Wake up the specified per-rcu_node-structure kthread.
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* Because the per-rcu_node kthreads are immortal, we don't need
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* to do anything to keep them alive.
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*/
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static void invoke_rcu_node_kthread(struct rcu_node *rnp)
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{
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struct task_struct *t;
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t = rnp->node_kthread_task;
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if (t != NULL)
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wake_up_process(t);
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}
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/*
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* Set the specified CPU's kthread to run RT or not, as specified by
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* the to_rt argument. The CPU-hotplug locks are held, so the task
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* is not going away.
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*/
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static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
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{
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int policy;
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struct sched_param sp;
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struct task_struct *t;
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t = per_cpu(rcu_cpu_kthread_task, cpu);
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if (t == NULL)
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return;
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if (to_rt) {
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policy = SCHED_FIFO;
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sp.sched_priority = RCU_KTHREAD_PRIO;
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} else {
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policy = SCHED_NORMAL;
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sp.sched_priority = 0;
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}
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sched_setscheduler_nocheck(t, policy, &sp);
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}
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/*
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* Timer handler to initiate the waking up of per-CPU kthreads that
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* have yielded the CPU due to excess numbers of RCU callbacks.
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* We wake up the per-rcu_node kthread, which in turn will wake up
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* the booster kthread.
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*/
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static void rcu_cpu_kthread_timer(unsigned long arg)
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{
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struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
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struct rcu_node *rnp = rdp->mynode;
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atomic_or(rdp->grpmask, &rnp->wakemask);
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invoke_rcu_node_kthread(rnp);
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}
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/*
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* Drop to non-real-time priority and yield, but only after posting a
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* timer that will cause us to regain our real-time priority if we
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* remain preempted. Either way, we restore our real-time priority
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* before returning.
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*/
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static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
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{
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struct sched_param sp;
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struct timer_list yield_timer;
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setup_timer_on_stack(&yield_timer, f, arg);
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mod_timer(&yield_timer, jiffies + 2);
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sp.sched_priority = 0;
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sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
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set_user_nice(current, 19);
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schedule();
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sp.sched_priority = RCU_KTHREAD_PRIO;
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sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
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del_timer(&yield_timer);
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}
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/*
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* Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU.
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* This can happen while the corresponding CPU is either coming online
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* or going offline. We cannot wait until the CPU is fully online
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* before starting the kthread, because the various notifier functions
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* can wait for RCU grace periods. So we park rcu_cpu_kthread() until
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* the corresponding CPU is online.
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*
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* Return 1 if the kthread needs to stop, 0 otherwise.
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*
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* Caller must disable bh. This function can momentarily enable it.
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*/
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static int rcu_cpu_kthread_should_stop(int cpu)
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{
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while (cpu_is_offline(cpu) ||
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!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) ||
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smp_processor_id() != cpu) {
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if (kthread_should_stop())
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return 1;
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per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
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per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id();
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local_bh_enable();
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schedule_timeout_uninterruptible(1);
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if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)))
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set_cpus_allowed_ptr(current, cpumask_of(cpu));
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local_bh_disable();
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}
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per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
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return 0;
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}
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/*
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* Per-CPU kernel thread that invokes RCU callbacks. This replaces the
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* earlier RCU softirq.
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*/
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static int rcu_cpu_kthread(void *arg)
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{
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int cpu = (int)(long)arg;
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unsigned long flags;
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int spincnt = 0;
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unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
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char work;
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char *workp = &per_cpu(rcu_cpu_has_work, cpu);
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for (;;) {
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*statusp = RCU_KTHREAD_WAITING;
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rcu_wait(*workp != 0 || kthread_should_stop());
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local_bh_disable();
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if (rcu_cpu_kthread_should_stop(cpu)) {
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local_bh_enable();
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break;
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}
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*statusp = RCU_KTHREAD_RUNNING;
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per_cpu(rcu_cpu_kthread_loops, cpu)++;
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local_irq_save(flags);
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work = *workp;
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*workp = 0;
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local_irq_restore(flags);
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if (work)
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rcu_kthread_do_work();
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local_bh_enable();
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if (*workp != 0)
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spincnt++;
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else
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spincnt = 0;
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if (spincnt > 10) {
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*statusp = RCU_KTHREAD_YIELDING;
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rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
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spincnt = 0;
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}
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}
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*statusp = RCU_KTHREAD_STOPPED;
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return 0;
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}
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/*
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* Spawn a per-CPU kthread, setting up affinity and priority.
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* Because the CPU hotplug lock is held, no other CPU will be attempting
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* to manipulate rcu_cpu_kthread_task. There might be another CPU
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* attempting to access it during boot, but the locking in kthread_bind()
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* will enforce sufficient ordering.
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*
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* Please note that we cannot simply refuse to wake up the per-CPU
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* kthread because kthreads are created in TASK_UNINTERRUPTIBLE state,
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* which can result in softlockup complaints if the task ends up being
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* idle for more than a couple of minutes.
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*
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* However, please note also that we cannot bind the per-CPU kthread to its
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* CPU until that CPU is fully online. We also cannot wait until the
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* CPU is fully online before we create its per-CPU kthread, as this would
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* deadlock the system when CPU notifiers tried waiting for grace
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* periods. So we bind the per-CPU kthread to its CPU only if the CPU
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* is online. If its CPU is not yet fully online, then the code in
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* rcu_cpu_kthread() will wait until it is fully online, and then do
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* the binding.
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*/
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static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
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{
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struct sched_param sp;
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struct task_struct *t;
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if (!rcu_kthreads_spawnable ||
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per_cpu(rcu_cpu_kthread_task, cpu) != NULL)
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return 0;
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t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu);
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if (IS_ERR(t))
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return PTR_ERR(t);
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if (cpu_online(cpu))
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kthread_bind(t, cpu);
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per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
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WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
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sp.sched_priority = RCU_KTHREAD_PRIO;
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sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
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per_cpu(rcu_cpu_kthread_task, cpu) = t;
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wake_up_process(t); /* Get to TASK_INTERRUPTIBLE quickly. */
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return 0;
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}
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/*
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* Per-rcu_node kthread, which is in charge of waking up the per-CPU
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* kthreads when needed. We ignore requests to wake up kthreads
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* for offline CPUs, which is OK because force_quiescent_state()
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* takes care of this case.
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*/
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static int rcu_node_kthread(void *arg)
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{
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int cpu;
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unsigned long flags;
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unsigned long mask;
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struct rcu_node *rnp = (struct rcu_node *)arg;
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struct sched_param sp;
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struct task_struct *t;
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for (;;) {
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rnp->node_kthread_status = RCU_KTHREAD_WAITING;
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rcu_wait(atomic_read(&rnp->wakemask) != 0);
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rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
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raw_spin_lock_irqsave(&rnp->lock, flags);
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mask = atomic_xchg(&rnp->wakemask, 0);
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rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
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for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
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if ((mask & 0x1) == 0)
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continue;
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preempt_disable();
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t = per_cpu(rcu_cpu_kthread_task, cpu);
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if (!cpu_online(cpu) || t == NULL) {
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preempt_enable();
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continue;
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}
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per_cpu(rcu_cpu_has_work, cpu) = 1;
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sp.sched_priority = RCU_KTHREAD_PRIO;
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sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
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preempt_enable();
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}
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}
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/* NOTREACHED */
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rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
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return 0;
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}
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/*
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* Set the per-rcu_node kthread's affinity to cover all CPUs that are
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* served by the rcu_node in question. The CPU hotplug lock is still
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* held, so the value of rnp->qsmaskinit will be stable.
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*
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* We don't include outgoingcpu in the affinity set, use -1 if there is
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* no outgoing CPU. If there are no CPUs left in the affinity set,
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* this function allows the kthread to execute on any CPU.
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*/
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static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
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{
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cpumask_var_t cm;
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int cpu;
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unsigned long mask = rnp->qsmaskinit;
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if (rnp->node_kthread_task == NULL)
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return;
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if (!alloc_cpumask_var(&cm, GFP_KERNEL))
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return;
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cpumask_clear(cm);
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for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
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if ((mask & 0x1) && cpu != outgoingcpu)
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cpumask_set_cpu(cpu, cm);
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if (cpumask_weight(cm) == 0) {
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cpumask_setall(cm);
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for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
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cpumask_clear_cpu(cpu, cm);
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WARN_ON_ONCE(cpumask_weight(cm) == 0);
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}
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set_cpus_allowed_ptr(rnp->node_kthread_task, cm);
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rcu_boost_kthread_setaffinity(rnp, cm);
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free_cpumask_var(cm);
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}
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/*
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* Spawn a per-rcu_node kthread, setting priority and affinity.
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* Called during boot before online/offline can happen, or, if
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* during runtime, with the main CPU-hotplug locks held. So only
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* one of these can be executing at a time.
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*/
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static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
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struct rcu_node *rnp)
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{
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unsigned long flags;
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int rnp_index = rnp - &rsp->node[0];
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struct sched_param sp;
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struct task_struct *t;
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if (!rcu_kthreads_spawnable ||
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rnp->qsmaskinit == 0)
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return 0;
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if (rnp->node_kthread_task == NULL) {
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t = kthread_create(rcu_node_kthread, (void *)rnp,
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"rcun%d", rnp_index);
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if (IS_ERR(t))
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return PTR_ERR(t);
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raw_spin_lock_irqsave(&rnp->lock, flags);
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rnp->node_kthread_task = t;
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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sp.sched_priority = 99;
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sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
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wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
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}
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return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
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}
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/*
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* Spawn all kthreads -- called as soon as the scheduler is running.
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*/
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static int __init rcu_spawn_kthreads(void)
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{
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int cpu;
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struct rcu_node *rnp;
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rcu_kthreads_spawnable = 1;
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for_each_possible_cpu(cpu) {
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per_cpu(rcu_cpu_has_work, cpu) = 0;
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if (cpu_online(cpu))
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(void)rcu_spawn_one_cpu_kthread(cpu);
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}
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rnp = rcu_get_root(rcu_state);
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(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
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if (NUM_RCU_NODES > 1) {
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rcu_for_each_leaf_node(rcu_state, rnp)
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(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
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}
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return 0;
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}
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early_initcall(rcu_spawn_kthreads);
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#else /* #ifdef CONFIG_RCU_BOOST */
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static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
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{
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}
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static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
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{
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}
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#endif /* #else #ifdef CONFIG_RCU_BOOST */
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static void
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__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
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struct rcu_state *rsp)
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@ -2243,29 +1885,6 @@ static void __cpuinit rcu_prepare_cpu(int cpu)
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rcu_preempt_init_percpu_data(cpu);
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}
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#ifdef CONFIG_RCU_BOOST
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static void __cpuinit rcu_prepare_kthreads(int cpu)
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{
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struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
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struct rcu_node *rnp = rdp->mynode;
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/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
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if (rcu_kthreads_spawnable) {
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(void)rcu_spawn_one_cpu_kthread(cpu);
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if (rnp->node_kthread_task == NULL)
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(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
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}
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}
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#else /* #ifdef CONFIG_RCU_BOOST */
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static void __cpuinit rcu_prepare_kthreads(int cpu)
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{
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}
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#endif /* #else #ifdef CONFIG_RCU_BOOST */
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/*
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* Handle CPU online/offline notification events.
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*/
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@ -427,6 +427,7 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
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#ifdef CONFIG_HOTPLUG_CPU
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static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
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unsigned long flags);
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static void rcu_stop_cpu_kthread(int cpu);
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#endif /* #ifdef CONFIG_HOTPLUG_CPU */
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static void rcu_print_detail_task_stall(struct rcu_state *rsp);
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static void rcu_print_task_stall(struct rcu_node *rnp);
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@ -460,6 +461,10 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
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static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
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struct rcu_node *rnp,
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int rnp_index);
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static void invoke_rcu_node_kthread(struct rcu_node *rnp);
|
||||
static void rcu_yield(void (*f)(unsigned long), unsigned long arg);
|
||||
#endif /* #ifdef CONFIG_RCU_BOOST */
|
||||
static void rcu_cpu_kthread_setrt(int cpu, int to_rt);
|
||||
static void __cpuinit rcu_prepare_kthreads(int cpu);
|
||||
|
||||
#endif /* #ifndef RCU_TREE_NONCORE */
|
||||
|
||||
@ -1330,6 +1330,370 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
|
||||
return 0;
|
||||
}
|
||||
|
||||
#ifdef CONFIG_HOTPLUG_CPU
|
||||
|
||||
/*
|
||||
* Stop the RCU's per-CPU kthread when its CPU goes offline,.
|
||||
*/
|
||||
static void rcu_stop_cpu_kthread(int cpu)
|
||||
{
|
||||
struct task_struct *t;
|
||||
|
||||
/* Stop the CPU's kthread. */
|
||||
t = per_cpu(rcu_cpu_kthread_task, cpu);
|
||||
if (t != NULL) {
|
||||
per_cpu(rcu_cpu_kthread_task, cpu) = NULL;
|
||||
kthread_stop(t);
|
||||
}
|
||||
}
|
||||
|
||||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
|
||||
static void rcu_kthread_do_work(void)
|
||||
{
|
||||
rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data));
|
||||
rcu_do_batch(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
|
||||
rcu_preempt_do_callbacks();
|
||||
}
|
||||
|
||||
/*
|
||||
* Wake up the specified per-rcu_node-structure kthread.
|
||||
* Because the per-rcu_node kthreads are immortal, we don't need
|
||||
* to do anything to keep them alive.
|
||||
*/
|
||||
static void invoke_rcu_node_kthread(struct rcu_node *rnp)
|
||||
{
|
||||
struct task_struct *t;
|
||||
|
||||
t = rnp->node_kthread_task;
|
||||
if (t != NULL)
|
||||
wake_up_process(t);
|
||||
}
|
||||
|
||||
/*
|
||||
* Set the specified CPU's kthread to run RT or not, as specified by
|
||||
* the to_rt argument. The CPU-hotplug locks are held, so the task
|
||||
* is not going away.
|
||||
*/
|
||||
static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
|
||||
{
|
||||
int policy;
|
||||
struct sched_param sp;
|
||||
struct task_struct *t;
|
||||
|
||||
t = per_cpu(rcu_cpu_kthread_task, cpu);
|
||||
if (t == NULL)
|
||||
return;
|
||||
if (to_rt) {
|
||||
policy = SCHED_FIFO;
|
||||
sp.sched_priority = RCU_KTHREAD_PRIO;
|
||||
} else {
|
||||
policy = SCHED_NORMAL;
|
||||
sp.sched_priority = 0;
|
||||
}
|
||||
sched_setscheduler_nocheck(t, policy, &sp);
|
||||
}
|
||||
|
||||
/*
|
||||
* Timer handler to initiate the waking up of per-CPU kthreads that
|
||||
* have yielded the CPU due to excess numbers of RCU callbacks.
|
||||
* We wake up the per-rcu_node kthread, which in turn will wake up
|
||||
* the booster kthread.
|
||||
*/
|
||||
static void rcu_cpu_kthread_timer(unsigned long arg)
|
||||
{
|
||||
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
|
||||
struct rcu_node *rnp = rdp->mynode;
|
||||
|
||||
atomic_or(rdp->grpmask, &rnp->wakemask);
|
||||
invoke_rcu_node_kthread(rnp);
|
||||
}
|
||||
|
||||
/*
|
||||
* Drop to non-real-time priority and yield, but only after posting a
|
||||
* timer that will cause us to regain our real-time priority if we
|
||||
* remain preempted. Either way, we restore our real-time priority
|
||||
* before returning.
|
||||
*/
|
||||
static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
|
||||
{
|
||||
struct sched_param sp;
|
||||
struct timer_list yield_timer;
|
||||
|
||||
setup_timer_on_stack(&yield_timer, f, arg);
|
||||
mod_timer(&yield_timer, jiffies + 2);
|
||||
sp.sched_priority = 0;
|
||||
sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
|
||||
set_user_nice(current, 19);
|
||||
schedule();
|
||||
sp.sched_priority = RCU_KTHREAD_PRIO;
|
||||
sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
|
||||
del_timer(&yield_timer);
|
||||
}
|
||||
|
||||
/*
|
||||
* Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU.
|
||||
* This can happen while the corresponding CPU is either coming online
|
||||
* or going offline. We cannot wait until the CPU is fully online
|
||||
* before starting the kthread, because the various notifier functions
|
||||
* can wait for RCU grace periods. So we park rcu_cpu_kthread() until
|
||||
* the corresponding CPU is online.
|
||||
*
|
||||
* Return 1 if the kthread needs to stop, 0 otherwise.
|
||||
*
|
||||
* Caller must disable bh. This function can momentarily enable it.
|
||||
*/
|
||||
static int rcu_cpu_kthread_should_stop(int cpu)
|
||||
{
|
||||
while (cpu_is_offline(cpu) ||
|
||||
!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) ||
|
||||
smp_processor_id() != cpu) {
|
||||
if (kthread_should_stop())
|
||||
return 1;
|
||||
per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
|
||||
per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id();
|
||||
local_bh_enable();
|
||||
schedule_timeout_uninterruptible(1);
|
||||
if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)))
|
||||
set_cpus_allowed_ptr(current, cpumask_of(cpu));
|
||||
local_bh_disable();
|
||||
}
|
||||
per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Per-CPU kernel thread that invokes RCU callbacks. This replaces the
|
||||
* earlier RCU softirq.
|
||||
*/
|
||||
static int rcu_cpu_kthread(void *arg)
|
||||
{
|
||||
int cpu = (int)(long)arg;
|
||||
unsigned long flags;
|
||||
int spincnt = 0;
|
||||
unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
|
||||
char work;
|
||||
char *workp = &per_cpu(rcu_cpu_has_work, cpu);
|
||||
|
||||
for (;;) {
|
||||
*statusp = RCU_KTHREAD_WAITING;
|
||||
rcu_wait(*workp != 0 || kthread_should_stop());
|
||||
local_bh_disable();
|
||||
if (rcu_cpu_kthread_should_stop(cpu)) {
|
||||
local_bh_enable();
|
||||
break;
|
||||
}
|
||||
*statusp = RCU_KTHREAD_RUNNING;
|
||||
per_cpu(rcu_cpu_kthread_loops, cpu)++;
|
||||
local_irq_save(flags);
|
||||
work = *workp;
|
||||
*workp = 0;
|
||||
local_irq_restore(flags);
|
||||
if (work)
|
||||
rcu_kthread_do_work();
|
||||
local_bh_enable();
|
||||
if (*workp != 0)
|
||||
spincnt++;
|
||||
else
|
||||
spincnt = 0;
|
||||
if (spincnt > 10) {
|
||||
*statusp = RCU_KTHREAD_YIELDING;
|
||||
rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
|
||||
spincnt = 0;
|
||||
}
|
||||
}
|
||||
*statusp = RCU_KTHREAD_STOPPED;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Spawn a per-CPU kthread, setting up affinity and priority.
|
||||
* Because the CPU hotplug lock is held, no other CPU will be attempting
|
||||
* to manipulate rcu_cpu_kthread_task. There might be another CPU
|
||||
* attempting to access it during boot, but the locking in kthread_bind()
|
||||
* will enforce sufficient ordering.
|
||||
*
|
||||
* Please note that we cannot simply refuse to wake up the per-CPU
|
||||
* kthread because kthreads are created in TASK_UNINTERRUPTIBLE state,
|
||||
* which can result in softlockup complaints if the task ends up being
|
||||
* idle for more than a couple of minutes.
|
||||
*
|
||||
* However, please note also that we cannot bind the per-CPU kthread to its
|
||||
* CPU until that CPU is fully online. We also cannot wait until the
|
||||
* CPU is fully online before we create its per-CPU kthread, as this would
|
||||
* deadlock the system when CPU notifiers tried waiting for grace
|
||||
* periods. So we bind the per-CPU kthread to its CPU only if the CPU
|
||||
* is online. If its CPU is not yet fully online, then the code in
|
||||
* rcu_cpu_kthread() will wait until it is fully online, and then do
|
||||
* the binding.
|
||||
*/
|
||||
static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
|
||||
{
|
||||
struct sched_param sp;
|
||||
struct task_struct *t;
|
||||
|
||||
if (!rcu_kthreads_spawnable ||
|
||||
per_cpu(rcu_cpu_kthread_task, cpu) != NULL)
|
||||
return 0;
|
||||
t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu);
|
||||
if (IS_ERR(t))
|
||||
return PTR_ERR(t);
|
||||
if (cpu_online(cpu))
|
||||
kthread_bind(t, cpu);
|
||||
per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
|
||||
WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
|
||||
sp.sched_priority = RCU_KTHREAD_PRIO;
|
||||
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
|
||||
per_cpu(rcu_cpu_kthread_task, cpu) = t;
|
||||
wake_up_process(t); /* Get to TASK_INTERRUPTIBLE quickly. */
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Per-rcu_node kthread, which is in charge of waking up the per-CPU
|
||||
* kthreads when needed. We ignore requests to wake up kthreads
|
||||
* for offline CPUs, which is OK because force_quiescent_state()
|
||||
* takes care of this case.
|
||||
*/
|
||||
static int rcu_node_kthread(void *arg)
|
||||
{
|
||||
int cpu;
|
||||
unsigned long flags;
|
||||
unsigned long mask;
|
||||
struct rcu_node *rnp = (struct rcu_node *)arg;
|
||||
struct sched_param sp;
|
||||
struct task_struct *t;
|
||||
|
||||
for (;;) {
|
||||
rnp->node_kthread_status = RCU_KTHREAD_WAITING;
|
||||
rcu_wait(atomic_read(&rnp->wakemask) != 0);
|
||||
rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
mask = atomic_xchg(&rnp->wakemask, 0);
|
||||
rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
|
||||
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
|
||||
if ((mask & 0x1) == 0)
|
||||
continue;
|
||||
preempt_disable();
|
||||
t = per_cpu(rcu_cpu_kthread_task, cpu);
|
||||
if (!cpu_online(cpu) || t == NULL) {
|
||||
preempt_enable();
|
||||
continue;
|
||||
}
|
||||
per_cpu(rcu_cpu_has_work, cpu) = 1;
|
||||
sp.sched_priority = RCU_KTHREAD_PRIO;
|
||||
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
|
||||
preempt_enable();
|
||||
}
|
||||
}
|
||||
/* NOTREACHED */
|
||||
rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Set the per-rcu_node kthread's affinity to cover all CPUs that are
|
||||
* served by the rcu_node in question. The CPU hotplug lock is still
|
||||
* held, so the value of rnp->qsmaskinit will be stable.
|
||||
*
|
||||
* We don't include outgoingcpu in the affinity set, use -1 if there is
|
||||
* no outgoing CPU. If there are no CPUs left in the affinity set,
|
||||
* this function allows the kthread to execute on any CPU.
|
||||
*/
|
||||
static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
|
||||
{
|
||||
cpumask_var_t cm;
|
||||
int cpu;
|
||||
unsigned long mask = rnp->qsmaskinit;
|
||||
|
||||
if (rnp->node_kthread_task == NULL)
|
||||
return;
|
||||
if (!alloc_cpumask_var(&cm, GFP_KERNEL))
|
||||
return;
|
||||
cpumask_clear(cm);
|
||||
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
|
||||
if ((mask & 0x1) && cpu != outgoingcpu)
|
||||
cpumask_set_cpu(cpu, cm);
|
||||
if (cpumask_weight(cm) == 0) {
|
||||
cpumask_setall(cm);
|
||||
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
|
||||
cpumask_clear_cpu(cpu, cm);
|
||||
WARN_ON_ONCE(cpumask_weight(cm) == 0);
|
||||
}
|
||||
set_cpus_allowed_ptr(rnp->node_kthread_task, cm);
|
||||
rcu_boost_kthread_setaffinity(rnp, cm);
|
||||
free_cpumask_var(cm);
|
||||
}
|
||||
|
||||
/*
|
||||
* Spawn a per-rcu_node kthread, setting priority and affinity.
|
||||
* Called during boot before online/offline can happen, or, if
|
||||
* during runtime, with the main CPU-hotplug locks held. So only
|
||||
* one of these can be executing at a time.
|
||||
*/
|
||||
static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
|
||||
struct rcu_node *rnp)
|
||||
{
|
||||
unsigned long flags;
|
||||
int rnp_index = rnp - &rsp->node[0];
|
||||
struct sched_param sp;
|
||||
struct task_struct *t;
|
||||
|
||||
if (!rcu_kthreads_spawnable ||
|
||||
rnp->qsmaskinit == 0)
|
||||
return 0;
|
||||
if (rnp->node_kthread_task == NULL) {
|
||||
t = kthread_create(rcu_node_kthread, (void *)rnp,
|
||||
"rcun%d", rnp_index);
|
||||
if (IS_ERR(t))
|
||||
return PTR_ERR(t);
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
rnp->node_kthread_task = t;
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
sp.sched_priority = 99;
|
||||
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
|
||||
wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
|
||||
}
|
||||
return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
|
||||
}
|
||||
|
||||
/*
|
||||
* Spawn all kthreads -- called as soon as the scheduler is running.
|
||||
*/
|
||||
static int __init rcu_spawn_kthreads(void)
|
||||
{
|
||||
int cpu;
|
||||
struct rcu_node *rnp;
|
||||
|
||||
rcu_kthreads_spawnable = 1;
|
||||
for_each_possible_cpu(cpu) {
|
||||
per_cpu(rcu_cpu_has_work, cpu) = 0;
|
||||
if (cpu_online(cpu))
|
||||
(void)rcu_spawn_one_cpu_kthread(cpu);
|
||||
}
|
||||
rnp = rcu_get_root(rcu_state);
|
||||
(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
|
||||
if (NUM_RCU_NODES > 1) {
|
||||
rcu_for_each_leaf_node(rcu_state, rnp)
|
||||
(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
early_initcall(rcu_spawn_kthreads);
|
||||
|
||||
static void __cpuinit rcu_prepare_kthreads(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
|
||||
struct rcu_node *rnp = rdp->mynode;
|
||||
|
||||
/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
|
||||
if (rcu_kthreads_spawnable) {
|
||||
(void)rcu_spawn_one_cpu_kthread(cpu);
|
||||
if (rnp->node_kthread_task == NULL)
|
||||
(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
|
||||
}
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_RCU_BOOST */
|
||||
|
||||
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
|
||||
@ -1346,6 +1710,26 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
|
||||
{
|
||||
}
|
||||
|
||||
#ifdef CONFIG_HOTPLUG_CPU
|
||||
|
||||
static void rcu_stop_cpu_kthread(int cpu)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
|
||||
static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
|
||||
{
|
||||
}
|
||||
|
||||
static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
|
||||
{
|
||||
}
|
||||
|
||||
static void __cpuinit rcu_prepare_kthreads(int cpu)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_RCU_BOOST */
|
||||
|
||||
#ifndef CONFIG_SMP
|
||||
|
||||
Loading…
Reference in New Issue
Block a user