rcu: Print scheduling-clock information on RCU CPU stall-warning messages
There have been situations where RCU CPU stall warnings were caused by
issues in scheduling-clock timer initialization. To make it easier to
track these down, this commit causes the RCU CPU stall-warning messages
to print out the number of scheduling-clock interrupts taken in the
current grace period for each stalled CPU.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index cfdab98..dccd2f7 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -689,12 +689,6 @@
return;
}
rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
-
- /*
- * Now rat on any tasks that got kicked up to the root rcu_node
- * due to CPU offlining.
- */
- ndetected = rcu_print_task_stall(rnp);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/*
@@ -702,8 +696,9 @@
* See Documentation/RCU/stallwarn.txt for info on how to debug
* RCU CPU stall warnings.
*/
- printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {",
+ printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:",
rsp->name);
+ print_cpu_stall_info_begin();
rcu_for_each_leaf_node(rsp, rnp) {
raw_spin_lock_irqsave(&rnp->lock, flags);
ndetected += rcu_print_task_stall(rnp);
@@ -712,11 +707,22 @@
continue;
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
if (rnp->qsmask & (1UL << cpu)) {
- printk(" %d", rnp->grplo + cpu);
+ print_cpu_stall_info(rsp, rnp->grplo + cpu);
ndetected++;
}
}
- printk("} (detected by %d, t=%ld jiffies)\n",
+
+ /*
+ * Now rat on any tasks that got kicked up to the root rcu_node
+ * due to CPU offlining.
+ */
+ rnp = rcu_get_root(rsp);
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ ndetected = rcu_print_task_stall(rnp);
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+ print_cpu_stall_info_end();
+ printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n",
smp_processor_id(), (long)(jiffies - rsp->gp_start));
if (ndetected == 0)
printk(KERN_ERR "INFO: Stall ended before state dump start\n");
@@ -740,8 +746,11 @@
* See Documentation/RCU/stallwarn.txt for info on how to debug
* RCU CPU stall warnings.
*/
- printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n",
- rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
+ printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name);
+ print_cpu_stall_info_begin();
+ print_cpu_stall_info(rsp, smp_processor_id());
+ print_cpu_stall_info_end();
+ printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start);
if (!trigger_all_cpu_backtrace())
dump_stack();
@@ -831,6 +840,7 @@
rdp->passed_quiesce = 0;
} else
rdp->qs_pending = 0;
+ zero_cpu_stall_ticks(rdp);
}
}
@@ -1496,6 +1506,7 @@
void rcu_check_callbacks(int cpu, int user)
{
trace_rcu_utilization("Start scheduler-tick");
+ increment_cpu_stall_ticks();
if (user || rcu_is_cpu_rrupt_from_idle()) {
/*
