Commit-ID: fc908ed33e7c1428f799abb12399f906da03b397
Gitweb: http://git.kernel.org/tip/fc908ed33e7c1428f799abb12399f906da03b397
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 8 Dec 2014 09:57:48 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 6 Jan 2015 11:05:25 -0800
rcu: Make RCU_CPU_STALL_INFO include number of fqs attempts
One way that an RCU CPU stall warning can happen is if the grace-period
kthread is not allowed to execute. One proxy for this kthread's
forward progress is the number of force-quiescent-state (fqs) scans.
This commit therefore adds the number of fqs scans to the RCU CPU stall
warning printouts when CONFIG_RCU_CPU_STALL_INFO=y.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 1 +
kernel/rcu/tree.h | 2 ++
kernel/rcu/tree_plugin.h | 3 ++-
3 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4c106fc..654b15b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1043,6 +1043,7 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
j1 = rcu_jiffies_till_stall_check();
ACCESS_ONCE(rsp->jiffies_stall) = j + j1;
rsp->jiffies_resched = j + j1 / 2;
+ rsp->n_force_qs_gpstart = ACCESS_ONCE(rsp->n_force_qs);
}
/*
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 8e7b184..e300848 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -492,6 +492,8 @@ struct rcu_state {
/* for CPU stalls. */
unsigned long jiffies_resched; /* Time at which to resched */
/* a reluctant CPU. */
+ unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
+ /* GP start. */
unsigned long gp_max; /* Maximum GP duration in */
/* jiffies. */
const char *name; /* Name of structure. */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 3ec85cb..769384d7 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1898,11 +1898,12 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
ticks_value = rsp->gpnum - rdp->gpnum;
}
print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
- pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n",
+ pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u fqs=%ld %s\n",
cpu, ticks_value, ticks_title,
atomic_read(&rdtp->dynticks) & 0xfff,
rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
+ ACCESS_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,
fast_no_hz);
}
--
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