Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 3acd9eb3 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Fix deadlock in TREE_PREEMPT_RCU CPU stall detection 



Under TREE_PREEMPT_RCU, print_other_cpu_stall() invokes
rcu_print_task_stall() with the root rcu_node structure's ->lock
held, and rcu_print_task_stall() acquires that same lock for
self-deadlock. Fix this by removing the lock acquisition from
rcu_print_task_stall(), and making all callers acquire the lock
instead.

Tested-by: default avatarJohn Kacur <jkacur@redhat.com>
Tested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Located-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-19-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 1304afb2

kernel/rcutree.c

+2 −0
Original line number Original line Diff line number Diff line
@@ -476,7 +476,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp) 




	printk(KERN_ERR "INFO: RCU detected CPU stalls:");

	printk(KERN_ERR "INFO: RCU detected CPU stalls:");

	rcu_for_each_leaf_node(rsp, rnp) {

	rcu_for_each_leaf_node(rsp, rnp) {

		raw_spin_lock_irqsave(&rnp->lock, flags);

		rcu_print_task_stall(rnp);

		rcu_print_task_stall(rnp);

		raw_spin_unlock_irqrestore(&rnp->lock, flags);

		if (rnp->qsmask == 0)

		if (rnp->qsmask == 0)

			continue;

			continue;

		for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)

		for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)

kernel/rcutree_plugin.h

+0 −3
Original line number Original line Diff line number Diff line
@@ -318,18 +318,15 @@ EXPORT_SYMBOL_GPL(__rcu_read_unlock); 
 */

 */

static void rcu_print_task_stall(struct rcu_node *rnp)

static void rcu_print_task_stall(struct rcu_node *rnp)

{

{

	unsigned long flags;

	struct list_head *lp;

	struct list_head *lp;

	int phase;

	int phase;

	struct task_struct *t;

	struct task_struct *t;





	if (rcu_preempted_readers(rnp)) {

	if (rcu_preempted_readers(rnp)) {

		raw_spin_lock_irqsave(&rnp->lock, flags);

		phase = rnp->gpnum & 0x1;

		phase = rnp->gpnum & 0x1;

		lp = &rnp->blocked_tasks[phase];

		lp = &rnp->blocked_tasks[phase];

		list_for_each_entry(t, lp, rcu_node_entry)

		list_for_each_entry(t, lp, rcu_node_entry)

			printk(" P%d", t->pid);

			printk(" P%d", t->pid);

		raw_spin_unlock_irqrestore(&rnp->lock, flags);

	}

	}

}

}