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Commit 9d55ab71 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull RCU fixes from Ingo Molnar:
 "This tree includes a shutdown/cpu-hotplug deadlock fix and a
  documentation fix."

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Advise most users not to enable RCU user mode
  rcu: Grace-period initialization excludes only RCU notifier
parents 4f1cd914 c1f8d901

init/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -496,6 +496,12 @@ config RCU_USER_QS 
	  excluded from the global RCU state machine and thus doesn't

	  to keep the timer tick on for RCU.



	  Unless you want to hack and help the development of the full

	  tickless feature, you shouldn't enable this option. It adds

	  unnecessary overhead.



	  If unsure say N



config RCU_USER_QS_FORCE

	bool "Force userspace extended QS by default"

	depends on RCU_USER_QS
@@ -504,6 +510,12 @@ config RCU_USER_QS_FORCE 
	  test this feature that treats userspace as an extended quiescent

	  state until we have a real user like a full adaptive nohz option.



	  Unless you want to hack and help the development of the full

	  tickless feature, you shouldn't enable this option. It adds

	  unnecessary overhead.



	  If unsure say N



config RCU_FANOUT

	int "Tree-based hierarchical RCU fanout value"

	range 2 64 if 64BIT

kernel/rcutree.c

+10 −11
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; 
	.orphan_nxttail = &sname##_state.orphan_nxtlist, \

	.orphan_donetail = &sname##_state.orphan_donelist, \

	.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \

	.onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \

	.name = #sname, \

}
@@ -1197,7 +1198,7 @@ static int rcu_gp_init(struct rcu_state *rsp) 
	raw_spin_unlock_irq(&rnp->lock);



	/* Exclude any concurrent CPU-hotplug operations. */

	get_online_cpus();

	mutex_lock(&rsp->onoff_mutex);



	/*

	 * Set the quiescent-state-needed bits in all the rcu_node
@@ -1234,7 +1235,7 @@ static int rcu_gp_init(struct rcu_state *rsp) 
		cond_resched();

	}



	put_online_cpus();

	mutex_unlock(&rsp->onoff_mutex);

	return 1;

}
@@ -1700,6 +1701,7 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) 
	/* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */



	/* Exclude any attempts to start a new grace period. */

	mutex_lock(&rsp->onoff_mutex);

	raw_spin_lock_irqsave(&rsp->onofflock, flags);



	/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
@@ -1744,6 +1746,7 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) 
	init_callback_list(rdp);

	/* Disallow further callbacks on this CPU. */

	rdp->nxttail[RCU_NEXT_TAIL] = NULL;

	mutex_unlock(&rsp->onoff_mutex);

}



#else /* #ifdef CONFIG_HOTPLUG_CPU */
@@ -2648,6 +2651,9 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) 
	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);

	struct rcu_node *rnp = rcu_get_root(rsp);



	/* Exclude new grace periods. */

	mutex_lock(&rsp->onoff_mutex);



	/* Set up local state, ensuring consistent view of global state. */

	raw_spin_lock_irqsave(&rnp->lock, flags);

	rdp->beenonline = 1;	 /* We have now been online. */
@@ -2662,14 +2668,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) 
	rcu_prepare_for_idle_init(cpu);

	raw_spin_unlock(&rnp->lock);		/* irqs remain disabled. */



	/*

	 * A new grace period might start here.  If so, we won't be part

	 * of it, but that is OK, as we are currently in a quiescent state.

	 */



	/* Exclude any attempts to start a new GP on large systems. */

	raw_spin_lock(&rsp->onofflock);		/* irqs already disabled. */



	/* Add CPU to rcu_node bitmasks. */

	rnp = rdp->mynode;

	mask = rdp->grpmask;
@@ -2693,8 +2691,9 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) 
		raw_spin_unlock(&rnp->lock); /* irqs already disabled. */

		rnp = rnp->parent;

	} while (rnp != NULL && !(rnp->qsmaskinit & mask));

	local_irq_restore(flags);



	raw_spin_unlock_irqrestore(&rsp->onofflock, flags);

	mutex_unlock(&rsp->onoff_mutex);

}



static void __cpuinit rcu_prepare_cpu(int cpu)

kernel/rcutree.h

+6 −0
Original line number Diff line number Diff line
@@ -394,11 +394,17 @@ struct rcu_state { 
	struct rcu_head **orphan_donetail;	/* Tail of above. */

	long qlen_lazy;				/* Number of lazy callbacks. */

	long qlen;				/* Total number of callbacks. */

	/* End of fields guarded by onofflock. */



	struct mutex onoff_mutex;		/* Coordinate hotplug & GPs. */



	struct mutex barrier_mutex;		/* Guards barrier fields. */

	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */

	struct completion barrier_completion;	/* Wake at barrier end. */

	unsigned long n_barrier_done;		/* ++ at start and end of */

						/*  _rcu_barrier(). */

	/* End of fields guarded by barrier_mutex. */



	unsigned long jiffies_force_qs;		/* Time at which to invoke */

						/*  force_quiescent_state(). */

	unsigned long n_force_qs;		/* Number of calls to */