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Commit eff9b713 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: fix locking cleanup fallout 



Given that the rcp->lock is now acquired from call_rcu(), which can be
invoked from irq-disable regions, all acquisitions need to disable irqs.
The following patch fixes this.

Although I don't have any reason to believe that this is the cause of
Yinghai's oops, it does need to be fixed.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ded00a56

kernel/rcuclassic.c

+22 −14
Original line number Diff line number Diff line
@@ -86,8 +86,10 @@ static void force_quiescent_state(struct rcu_data *rdp, 
{

	int cpu;

	cpumask_t cpumask;

	unsigned long flags;



	set_need_resched();

	spin_lock(&rcp->lock);

	spin_lock_irqsave(&rcp->lock, flags);

	if (unlikely(!rcp->signaled)) {

		rcp->signaled = 1;

		/*
@@ -113,7 +115,7 @@ static void force_quiescent_state(struct rcu_data *rdp, 
		for_each_cpu_mask_nr(cpu, cpumask)

			smp_send_reschedule(cpu);

	}

	spin_unlock(&rcp->lock);

	spin_unlock_irqrestore(&rcp->lock, flags);

}

#else

static inline void force_quiescent_state(struct rcu_data *rdp,
@@ -301,17 +303,18 @@ static void print_other_cpu_stall(struct rcu_ctrlblk *rcp) 
{

	int cpu;

	long delta;

	unsigned long flags;



	/* Only let one CPU complain about others per time interval. */



	spin_lock(&rcp->lock);

	spin_lock_irqsave(&rcp->lock, flags);

	delta = get_seconds() - rcp->gp_check;

	if (delta < 2L || cpus_empty(rcp->cpumask)) {

		spin_unlock(&rcp->lock);

		return;

	}

	rcp->gp_check = get_seconds() + 30;

	spin_unlock(&rcp->lock);

	spin_unlock_irqrestore(&rcp->lock, flags);



	/* OK, time to rat on our buddy... */
@@ -324,13 +327,15 @@ static void print_other_cpu_stall(struct rcu_ctrlblk *rcp) 


static void print_cpu_stall(struct rcu_ctrlblk *rcp)

{

	unsigned long flags;



	printk(KERN_ERR "RCU detected CPU %d stall (t=%lu/%lu)\n",

			smp_processor_id(), get_seconds(), rcp->gp_check);

	dump_stack();

	spin_lock(&rcp->lock);

	spin_lock_irqsave(&rcp->lock, flags);

	if ((long)(get_seconds() - rcp->gp_check) >= 0L)

		rcp->gp_check = get_seconds() + 30;

	spin_unlock(&rcp->lock);

	spin_unlock_irqrestore(&rcp->lock, flags);

}



static void check_cpu_stall(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
@@ -413,6 +418,8 @@ static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp) 
static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,

					struct rcu_data *rdp)

{

	unsigned long flags;



	if (rdp->quiescbatch != rcp->cur) {

		/* start new grace period: */

		rdp->qs_pending = 1;
@@ -436,7 +443,7 @@ static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, 
		return;

	rdp->qs_pending = 0;



	spin_lock(&rcp->lock);

	spin_lock_irqsave(&rcp->lock, flags);

	/*

	 * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync

	 * during cpu startup. Ignore the quiescent state.
@@ -444,7 +451,7 @@ static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, 
	if (likely(rdp->quiescbatch == rcp->cur))

		cpu_quiet(rdp->cpu, rcp);



	spin_unlock(&rcp->lock);

	spin_unlock_irqrestore(&rcp->lock, flags);

}
@@ -469,21 +476,22 @@ static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, 
static void __rcu_offline_cpu(struct rcu_data *this_rdp,

				struct rcu_ctrlblk *rcp, struct rcu_data *rdp)

{

	unsigned long flags;



	/*

	 * if the cpu going offline owns the grace period

	 * we can block indefinitely waiting for it, so flush

	 * it here

	 */

	spin_lock_bh(&rcp->lock);

	spin_lock_irqsave(&rcp->lock, flags);

	if (rcp->cur != rcp->completed)

		cpu_quiet(rdp->cpu, rcp);

	rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail, rcp->cur + 1);

	rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail[2], rcp->cur + 1);

	spin_unlock_bh(&rcp->lock);

	spin_unlock(&rcp->lock);



	local_irq_disable();

	this_rdp->qlen += rdp->qlen;

	local_irq_enable();

	local_irq_restore(flags);

}



static void rcu_offline_cpu(int cpu)
@@ -550,12 +558,12 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, 


		if (rcu_batch_after(rdp->batch, rcp->pending)) {

			/* and start it/schedule start if it's a new batch */

			spin_lock(&rcp->lock);

			spin_lock_irqsave(&rcp->lock, flags);

			if (rcu_batch_after(rdp->batch, rcp->pending)) {

				rcp->pending = rdp->batch;

				rcu_start_batch(rcp);

			}

			spin_unlock(&rcp->lock);

			spin_unlock_irqrestore(&rcp->lock, flags);

		}

	}