Commit 894d45bb authored by Mike Galbraith's avatar Mike Galbraith Committed by Paul E. McKenney
Browse files

rcu: Convert rcu_state.ofl_lock to raw_spinlock_t 



1e64b15a ("rcu: Fix grace-period hangs due to race with CPU offline")
added spinlock_t ofl_lock to the rcu_state structure, then takes it with
preemption disabled during CPU offline, which gives the -rt patchset's
sleeping spinlock heartburn.

This commit therefore converts ->ofl_lock to raw_spinlock_t.

Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
parent 8d8a9d0e

kernel/rcu/tree.c

+6 −6
Original line number Diff line number Diff line
@@ -97,7 +97,7 @@ struct rcu_state rcu_state = { 
	.abbr = RCU_ABBR,

	.exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex),

	.exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex),

	.ofl_lock = __SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),

	.ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),

};



/* Dump rcu_node combining tree at boot to verify correct setup. */
@@ -1776,13 +1776,13 @@ static bool rcu_gp_init(void) 
	 */

	rcu_state.gp_state = RCU_GP_ONOFF;

	rcu_for_each_leaf_node(rnp) {

		spin_lock(&rcu_state.ofl_lock);

		raw_spin_lock(&rcu_state.ofl_lock);

		raw_spin_lock_irq_rcu_node(rnp);

		if (rnp->qsmaskinit == rnp->qsmaskinitnext &&

		    !rnp->wait_blkd_tasks) {

			/* Nothing to do on this leaf rcu_node structure. */

			raw_spin_unlock_irq_rcu_node(rnp);

			spin_unlock(&rcu_state.ofl_lock);

			raw_spin_unlock(&rcu_state.ofl_lock);

			continue;

		}
@@ -1818,7 +1818,7 @@ static bool rcu_gp_init(void) 
		}



		raw_spin_unlock_irq_rcu_node(rnp);

		spin_unlock(&rcu_state.ofl_lock);

		raw_spin_unlock(&rcu_state.ofl_lock);

	}

	rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */
@@ -3377,7 +3377,7 @@ void rcu_report_dead(unsigned int cpu) 


	/* Remove outgoing CPU from mask in the leaf rcu_node structure. */

	mask = rdp->grpmask;

	spin_lock(&rcu_state.ofl_lock);

	raw_spin_lock(&rcu_state.ofl_lock);

	raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */

	rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);

	rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags);
@@ -3388,7 +3388,7 @@ void rcu_report_dead(unsigned int cpu) 
	}

	rnp->qsmaskinitnext &= ~mask;

	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

	spin_unlock(&rcu_state.ofl_lock);

	raw_spin_unlock(&rcu_state.ofl_lock);



	per_cpu(rcu_cpu_started, cpu) = 0;

}

kernel/rcu/tree.h

+1 −1
Original line number Diff line number Diff line
@@ -343,7 +343,7 @@ struct rcu_state { 
	const char *name;			/* Name of structure. */

	char abbr;				/* Abbreviated name. */



	spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;

	raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;

						/* Synchronize offline with */

						/*  GP pre-initialization. */

};

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