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Subject[PATCH v2] rcu: Dump all rcuc kthreads status for CPUs that not report quiescent state
Date
If the rcutree.use_softirq is configured, when RCU Stall event
happened, dump status of all rcuc kthreads who due to starvation
prevented grace period ends on CPUs that not report quiescent
state.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
---
v1->v2:
rework rcuc_kthread_dump function

kernel/rcu/tree_stall.h | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index d7956c03edbd..fcf0b2e1a71c 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -465,11 +465,13 @@ static void print_cpu_stall_info(int cpu)
falsepositive ? " (false positive?)" : "");
}

-static void rcuc_kthread_dump(struct rcu_data *rdp)
+static void __rcuc_kthread_dump(int cpu)
{
- int cpu;
- unsigned long j;
+ struct rcu_data *rdp;
struct task_struct *rcuc;
+ unsigned long j;
+
+ rdp = per_cpu_ptr(&rcu_data, cpu);

rcuc = rdp->rcu_cpu_kthread_task;
if (!rcuc)
@@ -488,6 +490,21 @@ static void rcuc_kthread_dump(struct rcu_data *rdp)
dump_cpu_task(cpu);
}

+static void rcuc_kthread_dump(void)
+{
+ int cpu;
+ struct rcu_node *rnp;
+ unsigned long flags;
+
+ rcu_for_each_leaf_node(rnp) {
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ for_each_leaf_node_possible_cpu(rnp, cpu)
+ if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
+ __rcuc_kthread_dump(cpu);
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ }
+}
+
/* Complain about starvation of grace-period kthread. */
static void rcu_check_gp_kthread_starvation(void)
{
@@ -597,6 +614,9 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
if (ndetected) {
rcu_dump_cpu_stacks();

+ if (!use_softirq)
+ rcuc_kthread_dump();
+
/* Complain about tasks blocking the grace period. */
rcu_for_each_leaf_node(rnp)
rcu_print_detail_task_stall_rnp(rnp);
@@ -659,11 +679,11 @@ static void print_cpu_stall(unsigned long gps)
rcu_check_gp_kthread_expired_fqs_timer();
rcu_check_gp_kthread_starvation();

- if (!use_softirq)
- rcuc_kthread_dump(rdp);
-
rcu_dump_cpu_stacks();

+ if (!use_softirq)
+ rcuc_kthread_dump();
+
raw_spin_lock_irqsave_rcu_node(rnp, flags);
/* Rewrite if needed in case of slow consoles. */
if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall)))
--
2.25.1
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