Gitweb: http://git.kernel.org/linus/3acd9eb31c5f7eb97cb2009fa41472710fb4a10f
Commit: 3acd9eb31c5f7eb97cb2009fa41472710fb4a10f
Parent: 1304afb225288a2e250d6a7495462c28e5509cbb
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Mon Feb 22 17:05:03 2010 -0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu Feb 25 10:34:59 2010 +0100
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: John Kacur <jkacur@redhat.com>
Tested-by: Thomas Gleixner <tglx@linutronix.de>
Located-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul 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: Ingo Molnar <mingo@elte.hu>
---
kernel/rcutree.c | 2 ++
kernel/rcutree_plugin.h | 3 ---
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 65a807b..b07be37 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -476,7 +476,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
printk(KERN_ERR "INFO: RCU detected CPU stalls:");
rcu_for_each_leaf_node(rsp, rnp) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
rcu_print_task_stall(rnp);
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
if (rnp->qsmask == 0)
continue;
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index a8b2e83..aecfe37 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -318,18 +318,15 @@ EXPORT_SYMBOL_GPL(__rcu_read_unlock);
*/
static void rcu_print_task_stall(struct rcu_node *rnp)
{
- unsigned long flags;
struct list_head *lp;
int phase;
struct task_struct *t;
if (rcu_preempted_readers(rnp)) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
phase = rnp->gpnum & 0x1;
lp = &rnp->blocked_tasks[phase];
list_for_each_entry(t, lp, rcu_node_entry)
printk(" P%d", t->pid);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
}
--
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