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Subject[PATCH RFC tip/core/rcu 12/16] rcu: disable CPU stall warnings upon panic
Date
The current RCU CPU stall warnings remain enabled even after a panic
occurs, which some people have found to be a bit counterproductive.
This patch therefore uses a notifier to disable stall warnings once a
panic occurs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 24 ++++++++++++++++++++++++
1 files changed, 24 insertions(+), 0 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3623f8e..595fb83 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -449,6 +449,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

+int rcu_cpu_stall_panicking __read_mostly;
+
static void record_gp_stall_check_time(struct rcu_state *rsp)
{
rsp->gp_start = jiffies;
@@ -526,6 +528,8 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
long delta;
struct rcu_node *rnp;

+ if (rcu_cpu_stall_panicking)
+ return;
delta = jiffies - rsp->jiffies_stall;
rnp = rdp->mynode;
if ((rnp->qsmask & rdp->grpmask) && delta >= 0) {
@@ -540,6 +544,21 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
}
}

+static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
+{
+ rcu_cpu_stall_panicking = 1;
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block rcu_panic_block = {
+ .notifier_call = rcu_panic,
+};
+
+static void __init check_cpu_stall_init(void)
+{
+ atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
+}
+
#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

static void record_gp_stall_check_time(struct rcu_state *rsp)
@@ -550,6 +569,10 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
{
}

+static void __init check_cpu_stall_init(void)
+{
+}
+
#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

/*
@@ -1934,6 +1957,7 @@ void __init rcu_init(void)
cpu_notifier(rcu_cpu_notify, 0);
for_each_online_cpu(cpu)
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
+ check_cpu_stall_init();
}

#include "rcutree_plugin.h"
--
1.7.0


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