Re: [PATCH RFC] v2 not-so-expedited "big hammer" RCU grace periods

[Mathieu Desnoyers]

* Paul E. McKenney (paulmck@xxxxxxxxxxxxxxxxxx) wrote:
> Third cut of "big hammer" expedited RCU grace periods, this time including
> rcu rather than just rcu_bh.  This uses resched IPIs to force quiescent
> states on other CPUs.  This particular variant uses smp_call_function() to
> invoke set_need_resched() on all CPUs in order to cause this to happen.
> Track the CPUs that have passed through a quiescent state (or gone
> offline) with a cpumask.
> 
> Does nothing to expedite callbacks already registered with call_rcu() or
> call_rcu_bh(), but there is no need to.  Just maps to synchronize_rcu()
> and a new synchronize_rcu_bh() on preemptable RCU, which has more complex
> grace-period detection -- this can be fixed later.
> 
> Passes light rcutorture testing.  Grace periods take many milliseconds
> on a variety of machines with a number of different config option
> combinations -- in other words, this implementation just does not cut it.
> Not even close.
> 
> I am posting it on the off-chance that I made some stupid mistake that
> someone might spot.  Absent that, I am taking a different approach, namely
> adapting the synchronize_sched() implementation from preemptable RCU.
> Evgeniy might have been suggesting something similar, and Mathieu seemed
> to be thinking along these lines as well.
> 
> Shortcomings:
> 
> o	Waaaaay too slow!!!  Again, thinking in terms of using
> 	preemptable RCU's synchronize_sched() implementation.
> 
> o	Does not address preemptable RCU.
> 
> Changes since v2:
> 
> o	Use reschedule IPIs rather than a softirq.
> 
> Changes since v1:
> 
> o	Added rcutorture support, and added exports required by
> 	rcutorture.
> 
> o	Added comment stating that smp_call_function() implies a
> 	memory barrier, suggested by Mathieu.
> 
> o	Added #include for delay.h.
> 
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> ---
> 
>  include/linux/rcupdate.h |    4 
>  kernel/rcuclassic.c      |    1 
>  kernel/rcupdate.c        |  179 +++++++++++++++++++++++++++++++++++++++++
>  kernel/rcutorture.c      |  205 +++++++++++++++++++++++++----------------------
>  kernel/rcutree.c         |    1 
>  5 files changed, 298 insertions(+), 92 deletions(-)
> 
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 15fbb3c..b630f14 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -264,10 +264,14 @@ extern void synchronize_rcu(void);
>  extern void rcu_barrier(void);
>  extern void rcu_barrier_bh(void);
>  extern void rcu_barrier_sched(void);
> +extern void synchronize_rcu_expedited(void);
> +extern void synchronize_rcu_bh_expedited(void);
> +extern long rcu_batches_completed_bh_expedited(void);
>  
>  /* Internal to kernel */
>  extern void rcu_init(void);
>  extern void rcu_scheduler_starting(void);
>  extern int rcu_needs_cpu(int cpu);
> +extern void synchronize_rcu_expedited_qs(int cpu);
>  
>  #endif /* __LINUX_RCUPDATE_H */
> diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
> index 0f2b0b3..d15bd62 100644
> --- a/kernel/rcuclassic.c
> +++ b/kernel/rcuclassic.c
> @@ -87,6 +87,7 @@ void rcu_qsctr_inc(int cpu)
>  {
>  	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
>  	rdp->passed_quiesc = 1;
> +	synchronize_rcu_expedited_qs(cpu);
>  }
>  
>  void rcu_bh_qsctr_inc(int cpu)
> diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
> index a967c9f..20fd5da 100644
> --- a/kernel/rcupdate.c
> +++ b/kernel/rcupdate.c
> @@ -45,6 +45,7 @@
>  #include <linux/mutex.h>
>  #include <linux/module.h>
>  #include <linux/kernel_stat.h>
> +#include <linux/delay.h>
>  
>  enum rcu_barrier {
>  	RCU_BARRIER_STD,
> @@ -98,6 +99,30 @@ void synchronize_rcu(void)
>  }
>  EXPORT_SYMBOL_GPL(synchronize_rcu);
>  
> +/**
> + * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
> + *
> + * Control will return to the caller some time after a full rcu_bh grace
> + * period has elapsed, in other words after all currently executing rcu_bh
> + * read-side critical sections have completed.  RCU read-side critical
> + * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
> + * and may be nested.
> + */
> +void synchronize_rcu_bh(void)
> +{
> +	struct rcu_synchronize rcu;
> +
> +	if (rcu_blocking_is_gp())
> +		return;
> +
> +	init_completion(&rcu.completion);
> +	/* Will wake me after RCU finished. */
> +	call_rcu_bh(&rcu.head, wakeme_after_rcu);
> +	/* Wait for it. */
> +	wait_for_completion(&rcu.completion);
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
> +
>  static void rcu_barrier_callback(struct rcu_head *notused)
>  {
>  	if (atomic_dec_and_test(&rcu_barrier_cpu_count))
> @@ -217,10 +242,164 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
>  	return NOTIFY_OK;
>  }
>  
> +static DEFINE_MUTEX(synchronize_rcu_bh_mutex);
> +static long synchronize_rcu_bh_completed; /* Expedited-grace-period count. */
> +
> +long rcu_batches_completed_bh_expedited(void)
> +{
> +	return synchronize_rcu_bh_completed;
> +}
> +EXPORT_SYMBOL_GPL(rcu_batches_completed_bh_expedited);
> +
> +#if !defined(CONFIG_SMP)
> +
> +void synchronize_rcu_expedited_qs(int cpu)
> +{
> +}
> +
> +static void __init synchronize_rcu_expedited_init(void)
> +{
> +}
> +
> +void synchronize_rcu_expedited(void)
> +{
> +	mutex_lock(&synchronize_rcu_bh_mutex);
> +	synchronize_rcu_bh_completed++;
> +	mutex_unlock(&synchronize_rcu_bh_mutex);
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
> +
> +void synchronize_rcu_bh_expedited(void)
> +{
> +	synchronize_rcu_expedited();
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_bh_expedited);
> +
> +#elif defined(CONFIG_PREEMPT_RCU)
> +
> +static void __init synchronize_rcu_expedited_init(void)
> +{
> +}
> +
> +void synchronize_rcu_expedited(void)
> +{
> +	synchronize_rcu();
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
> +
> +void synchronize_rcu_bh_expedited(void)
> +{
> +	synchronize_rcu_bh();
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_bh_expedited);
> +
> +#else
> +
> +static DEFINE_PER_CPU(int, rcu_expedited_need_qs);
> +static cpumask_var_t rcu_bh_waiting_map;
> +
> +void synchronize_rcu_expedited_qs(int cpu)
> +{
> +	smp_mb();
> +	per_cpu(rcu_expedited_need_qs, cpu) = 0;
> +	smp_mb();
> +}
> +
> +static void __init synchronize_rcu_expedited_init(void)
> +{
> +	alloc_bootmem_cpumask_var(&rcu_bh_waiting_map);
> +}
> +
> +static void rcu_set_need_resched(void *unused)
> +{
> +	set_need_resched();
> +}
> +
> +void synchronize_rcu_expedited(void)
> +{
> +	int cpu;
> +	int done;
> +	int times = 0;
> +
> +	mutex_lock(&synchronize_rcu_bh_mutex);
> +
> +	/* Take snapshot of online CPUs, blocking CPU hotplug. */
> +	preempt_disable();
> +	cpumask_copy(rcu_bh_waiting_map, &cpu_online_map);
> +	cpumask_clear_cpu(smp_processor_id(), rcu_bh_waiting_map);
> +	preempt_enable();
> +
> +	/*
> +	 * Mark each online CPU as needing a quiescent state and make
> +	 * each do a set_need_resched().
> +	 */
> +	smp_mb(); /* Ensure prior changes seen before setting flag below. */
> +	for_each_cpu(cpu, rcu_bh_waiting_map) {
> +		preempt_disable();
> +		per_cpu(rcu_expedited_need_qs, cpu) = 1;
> +		preempt_enable();
> +	}
> +	smp_call_function(rcu_set_need_resched, NULL, 1);
> +	udelay(10); /* let IPIs actually get to their destinations. */
> +
> +	/*
> +	 * Loop waiting for each CPU to either pass through a quiescent
> +	 * state or to go offline.  We don't care which.
> +	 */
> +	for (;;) {
> +		
> +		/* Ignore CPUs that are now offline, w/CPU hotplug blocked. */
> +		preempt_disable();
> +		cpumask_and(rcu_bh_waiting_map, rcu_bh_waiting_map,
> +			    &cpu_online_map);
> +		cpumask_clear_cpu(smp_processor_id(), rcu_bh_waiting_map);
> +		preempt_enable();
> +
> +		/* Check if any CPUs still need a quiescent state. */
> +		done = 1;
> +		for_each_cpu(cpu, rcu_bh_waiting_map) {
> +			preempt_disable();
> +			if (!cpumask_test_cpu(cpu, &cpu_online_map) ||
> +			    !per_cpu(rcu_expedited_need_qs, cpu))
> +				cpumask_clear_cpu(cpu, rcu_bh_waiting_map);
> +			else {
> +				done = 0;
> +				smp_send_reschedule(cpu);
> +			}
> +			preempt_enable();
> +		}
> +		if (done)
> +			break;
> +
> +		/*
> +		 * Wait a bit.  If we have already waited a fair
> +		 * amount of time, sleep.
> +		 */
> +		if (++times < 10)
> +			udelay(10 * times);
> +		else
> +			schedule_timeout_uninterruptible(1);

Waiting a whole jiffy (e.g. 1ms, 4ms, 10ms) here seems like a big hammer
to nail a delicate pin. I would not be surprised if your long delay
would come from here. Is it possible that your ipi+scheduling delay is
actually longer than the 11 udelays you are doing and that you end up
calling schedule_timeout_uninterruptible(1) each time ?

Mathieu

> +		/* FIXME: need to complain about holdout CPUs if too long. */
> +	}
> +
> +	synchronize_rcu_bh_completed++;
> +	mutex_unlock(&synchronize_rcu_bh_mutex);
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
> +
> +void synchronize_rcu_bh_expedited(void)
> +{
> +	synchronize_rcu_expedited();
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_bh_expedited);
> +
> +#endif /* #else #ifndef CONFIG_SMP */
> +
>  void __init rcu_init(void)
>  {
>  	__rcu_init();
>  	hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
> +	synchronize_rcu_expedited_init();
>  }
>  
>  void rcu_scheduler_starting(void)
> diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
> index 9b4a975..8845936 100644
> --- a/kernel/rcutorture.c
> +++ b/kernel/rcutorture.c
> @@ -257,14 +257,14 @@ struct rcu_torture_ops {
>  	void (*init)(void);
>  	void (*cleanup)(void);
>  	int (*readlock)(void);
> -	void (*readdelay)(struct rcu_random_state *rrsp);
> +	void (*read_delay)(struct rcu_random_state *rrsp);
>  	void (*readunlock)(int idx);
>  	int (*completed)(void);
> -	void (*deferredfree)(struct rcu_torture *p);
> +	void (*deferred_free)(struct rcu_torture *p);
>  	void (*sync)(void);
>  	void (*cb_barrier)(void);
>  	int (*stats)(char *page);
> -	int irqcapable;
> +	int irq_capable;
>  	char *name;
>  };
>  static struct rcu_torture_ops *cur_ops = NULL;
> @@ -320,7 +320,7 @@ rcu_torture_cb(struct rcu_head *p)
>  		rp->rtort_mbtest = 0;
>  		rcu_torture_free(rp);
>  	} else
> -		cur_ops->deferredfree(rp);
> +		cur_ops->deferred_free(rp);
>  }
>  
>  static void rcu_torture_deferred_free(struct rcu_torture *p)
> @@ -329,18 +329,18 @@ static void rcu_torture_deferred_free(struct rcu_torture *p)
>  }
>  
>  static struct rcu_torture_ops rcu_ops = {
> -	.init = NULL,
> -	.cleanup = NULL,
> -	.readlock = rcu_torture_read_lock,
> -	.readdelay = rcu_read_delay,
> -	.readunlock = rcu_torture_read_unlock,
> -	.completed = rcu_torture_completed,
> -	.deferredfree = rcu_torture_deferred_free,
> -	.sync = synchronize_rcu,
> -	.cb_barrier = rcu_barrier,
> -	.stats = NULL,
> -	.irqcapable = 1,
> -	.name = "rcu"
> +	.init		= NULL,
> +	.cleanup	= NULL,
> +	.readlock	= rcu_torture_read_lock,
> +	.read_delay	= rcu_read_delay,
> +	.readunlock	= rcu_torture_read_unlock,
> +	.completed	= rcu_torture_completed,
> +	.deferred_free	= rcu_torture_deferred_free,
> +	.sync		= synchronize_rcu,
> +	.cb_barrier	= rcu_barrier,
> +	.stats		= NULL,
> +	.irq_capable 	= 1,
> +	.name 		= "rcu"
>  };
>  
>  static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
> @@ -370,18 +370,18 @@ static void rcu_sync_torture_init(void)
>  }
>  
>  static struct rcu_torture_ops rcu_sync_ops = {
> -	.init = rcu_sync_torture_init,
> -	.cleanup = NULL,
> -	.readlock = rcu_torture_read_lock,
> -	.readdelay = rcu_read_delay,
> -	.readunlock = rcu_torture_read_unlock,
> -	.completed = rcu_torture_completed,
> -	.deferredfree = rcu_sync_torture_deferred_free,
> -	.sync = synchronize_rcu,
> -	.cb_barrier = NULL,
> -	.stats = NULL,
> -	.irqcapable = 1,
> -	.name = "rcu_sync"
> +	.init		= rcu_sync_torture_init,
> +	.cleanup	= NULL,
> +	.readlock	= rcu_torture_read_lock,
> +	.read_delay	= rcu_read_delay,
> +	.readunlock	= rcu_torture_read_unlock,
> +	.completed	= rcu_torture_completed,
> +	.deferred_free	= rcu_sync_torture_deferred_free,
> +	.sync		= synchronize_rcu,
> +	.cb_barrier	= NULL,
> +	.stats		= NULL,
> +	.irq_capable	= 1,
> +	.name		= "rcu_sync"
>  };
>  
>  /*
> @@ -432,33 +432,53 @@ static void rcu_bh_torture_synchronize(void)
>  }
>  
>  static struct rcu_torture_ops rcu_bh_ops = {
> -	.init = NULL,
> -	.cleanup = NULL,
> -	.readlock = rcu_bh_torture_read_lock,
> -	.readdelay = rcu_read_delay,  /* just reuse rcu's version. */
> -	.readunlock = rcu_bh_torture_read_unlock,
> -	.completed = rcu_bh_torture_completed,
> -	.deferredfree = rcu_bh_torture_deferred_free,
> -	.sync = rcu_bh_torture_synchronize,
> -	.cb_barrier = rcu_barrier_bh,
> -	.stats = NULL,
> -	.irqcapable = 1,
> -	.name = "rcu_bh"
> +	.init		= NULL,
> +	.cleanup	= NULL,
> +	.readlock	= rcu_bh_torture_read_lock,
> +	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
> +	.readunlock	= rcu_bh_torture_read_unlock,
> +	.completed	= rcu_bh_torture_completed,
> +	.deferred_free	= rcu_bh_torture_deferred_free,
> +	.sync		= rcu_bh_torture_synchronize,
> +	.cb_barrier	= rcu_barrier_bh,
> +	.stats		= NULL,
> +	.irq_capable	= 1,
> +	.name		= "rcu_bh"
>  };
>  
>  static struct rcu_torture_ops rcu_bh_sync_ops = {
> -	.init = rcu_sync_torture_init,
> -	.cleanup = NULL,
> -	.readlock = rcu_bh_torture_read_lock,
> -	.readdelay = rcu_read_delay,  /* just reuse rcu's version. */
> -	.readunlock = rcu_bh_torture_read_unlock,
> -	.completed = rcu_bh_torture_completed,
> -	.deferredfree = rcu_sync_torture_deferred_free,
> -	.sync = rcu_bh_torture_synchronize,
> -	.cb_barrier = NULL,
> -	.stats = NULL,
> -	.irqcapable = 1,
> -	.name = "rcu_bh_sync"
> +	.init		= rcu_sync_torture_init,
> +	.cleanup	= NULL,
> +	.readlock	= rcu_bh_torture_read_lock,
> +	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
> +	.readunlock	= rcu_bh_torture_read_unlock,
> +	.completed	= rcu_bh_torture_completed,
> +	.deferred_free	= rcu_sync_torture_deferred_free,
> +	.sync		= rcu_bh_torture_synchronize,
> +	.cb_barrier	= NULL,
> +	.stats		= NULL,
> +	.irq_capable	= 1,
> +	.name		= "rcu_bh_sync"
> +};
> +
> +static int rcu_bh_expedited_torture_completed(void)
> +{
> +	return rcu_batches_completed_bh_expedited();
> +}
> +
> +static struct rcu_torture_ops rcu_bh_expedited_ops = {
> +	.init		= rcu_sync_torture_init,
> +	.cleanup	= NULL,
> +	.readlock	= rcu_bh_torture_read_lock,
> +	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
> +	.readunlock	= rcu_bh_torture_read_unlock,
> +	.completed	= rcu_bh_expedited_torture_completed,
> +	.deferred_free	= rcu_sync_torture_deferred_free,
> +	.sync		= synchronize_rcu_bh_expedited,
> +	.cb_barrier	= NULL,
> +	.stats		= NULL,
> +	.irq_capable	= 1,
> +	.name		= "rcu_bh_expedited"
>  };
>  
>  /*
> @@ -530,17 +550,17 @@ static int srcu_torture_stats(char *page)
>  }
>  
>  static struct rcu_torture_ops srcu_ops = {
> -	.init = srcu_torture_init,
> -	.cleanup = srcu_torture_cleanup,
> -	.readlock = srcu_torture_read_lock,
> -	.readdelay = srcu_read_delay,
> -	.readunlock = srcu_torture_read_unlock,
> -	.completed = srcu_torture_completed,
> -	.deferredfree = rcu_sync_torture_deferred_free,
> -	.sync = srcu_torture_synchronize,
> -	.cb_barrier = NULL,
> -	.stats = srcu_torture_stats,
> -	.name = "srcu"
> +	.init		= srcu_torture_init,
> +	.cleanup	= srcu_torture_cleanup,
> +	.readlock	= srcu_torture_read_lock,
> +	.read_delay	= srcu_read_delay,
> +	.readunlock	= srcu_torture_read_unlock,
> +	.completed	= srcu_torture_completed,
> +	.deferred_free	= rcu_sync_torture_deferred_free,
> +	.sync		= srcu_torture_synchronize,
> +	.cb_barrier	= NULL,
> +	.stats		= srcu_torture_stats,
> +	.name		= "srcu"
>  };
>  
>  /*
> @@ -574,32 +594,32 @@ static void sched_torture_synchronize(void)
>  }
>  
>  static struct rcu_torture_ops sched_ops = {
> -	.init = rcu_sync_torture_init,
> -	.cleanup = NULL,
> -	.readlock = sched_torture_read_lock,
> -	.readdelay = rcu_read_delay,  /* just reuse rcu's version. */
> -	.readunlock = sched_torture_read_unlock,
> -	.completed = sched_torture_completed,
> -	.deferredfree = rcu_sched_torture_deferred_free,
> -	.sync = sched_torture_synchronize,
> -	.cb_barrier = rcu_barrier_sched,
> -	.stats = NULL,
> -	.irqcapable = 1,
> -	.name = "sched"
> +	.init		= rcu_sync_torture_init,
> +	.cleanup	= NULL,
> +	.readlock	= sched_torture_read_lock,
> +	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
> +	.readunlock	= sched_torture_read_unlock,
> +	.completed	= sched_torture_completed,
> +	.deferred_free	= rcu_sched_torture_deferred_free,
> +	.sync		= sched_torture_synchronize,
> +	.cb_barrier	= rcu_barrier_sched,
> +	.stats		= NULL,
> +	.irq_capable	= 1,
> +	.name		= "sched"
>  };
>  
>  static struct rcu_torture_ops sched_ops_sync = {
> -	.init = rcu_sync_torture_init,
> -	.cleanup = NULL,
> -	.readlock = sched_torture_read_lock,
> -	.readdelay = rcu_read_delay,  /* just reuse rcu's version. */
> -	.readunlock = sched_torture_read_unlock,
> -	.completed = sched_torture_completed,
> -	.deferredfree = rcu_sync_torture_deferred_free,
> -	.sync = sched_torture_synchronize,
> -	.cb_barrier = NULL,
> -	.stats = NULL,
> -	.name = "sched_sync"
> +	.init		= rcu_sync_torture_init,
> +	.cleanup	= NULL,
> +	.readlock	= sched_torture_read_lock,
> +	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
> +	.readunlock	= sched_torture_read_unlock,
> +	.completed	= sched_torture_completed,
> +	.deferred_free	= rcu_sync_torture_deferred_free,
> +	.sync		= sched_torture_synchronize,
> +	.cb_barrier	= NULL,
> +	.stats		= NULL,
> +	.name		= "sched_sync"
>  };
>  
>  /*
> @@ -635,7 +655,7 @@ rcu_torture_writer(void *arg)
>  				i = RCU_TORTURE_PIPE_LEN;
>  			atomic_inc(&rcu_torture_wcount[i]);
>  			old_rp->rtort_pipe_count++;
> -			cur_ops->deferredfree(old_rp);
> +			cur_ops->deferred_free(old_rp);
>  		}
>  		rcu_torture_current_version++;
>  		oldbatch = cur_ops->completed();
> @@ -700,7 +720,7 @@ static void rcu_torture_timer(unsigned long unused)
>  	if (p->rtort_mbtest == 0)
>  		atomic_inc(&n_rcu_torture_mberror);
>  	spin_lock(&rand_lock);
> -	cur_ops->readdelay(&rand);
> +	cur_ops->read_delay(&rand);
>  	n_rcu_torture_timers++;
>  	spin_unlock(&rand_lock);
>  	preempt_disable();
> @@ -738,11 +758,11 @@ rcu_torture_reader(void *arg)
>  
>  	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
>  	set_user_nice(current, 19);
> -	if (irqreader && cur_ops->irqcapable)
> +	if (irqreader && cur_ops->irq_capable)
>  		setup_timer_on_stack(&t, rcu_torture_timer, 0);
>  
>  	do {
> -		if (irqreader && cur_ops->irqcapable) {
> +		if (irqreader && cur_ops->irq_capable) {
>  			if (!timer_pending(&t))
>  				mod_timer(&t, 1);
>  		}
> @@ -757,7 +777,7 @@ rcu_torture_reader(void *arg)
>  		}
>  		if (p->rtort_mbtest == 0)
>  			atomic_inc(&n_rcu_torture_mberror);
> -		cur_ops->readdelay(&rand);
> +		cur_ops->read_delay(&rand);
>  		preempt_disable();
>  		pipe_count = p->rtort_pipe_count;
>  		if (pipe_count > RCU_TORTURE_PIPE_LEN) {
> @@ -778,7 +798,7 @@ rcu_torture_reader(void *arg)
>  	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
>  	VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
>  	rcutorture_shutdown_absorb("rcu_torture_reader");
> -	if (irqreader && cur_ops->irqcapable)
> +	if (irqreader && cur_ops->irq_capable)
>  		del_timer_sync(&t);
>  	while (!kthread_should_stop())
>  		schedule_timeout_uninterruptible(1);
> @@ -1078,6 +1098,7 @@ rcu_torture_init(void)
>  	int firsterr = 0;
>  	static struct rcu_torture_ops *torture_ops[] =
>  		{ &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
> +		  &rcu_bh_expedited_ops,
>  		  &srcu_ops, &sched_ops, &sched_ops_sync, };
>  
>  	mutex_lock(&fullstop_mutex);
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index d2a372f..bf2c21d 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -89,6 +89,7 @@ void rcu_qsctr_inc(int cpu)
>  	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
>  	rdp->passed_quiesc = 1;
>  	rdp->passed_quiesc_completed = rdp->completed;
> +	synchronize_rcu_expedited_qs(cpu);
>  }
>  
>  void rcu_bh_qsctr_inc(int cpu)

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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