From: Zqiang <qiang.zhang@linux.dev>
To: paulmck@kernel.org, frederic@kernel.org,
neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com,
urezki@gmail.com, boqun@kernel.org
Cc: qiang.zhang@linux.dev, rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] rcu-tasks: Dump rtpcp->lazy_timer status in show_rcu_tasks_generic_gp_kthread()
Date: Thu, 16 Jul 2026 17:57:54 +0800 [thread overview]
Message-ID: <20260716095754.24827-1-qiang.zhang@linux.dev> (raw)
Add 'P' flag to the diagnostic line to indicate whether any per-cpu
rtpcp's lazy_timer is pending. this helps diagnose stalls where
rcu-task callbacks are queued but the kthread stay sleep because
the lazy_timer has not yet fired and no grace period has started.
The output is as follows:
[ 31.319540][ T77] call_rcu_tasks() has failed boot-time tests.
[ 31.320205][ T77] rcu_tasks: RTGS_WAIT_CBS(11) since 7518 g:4 i:0 kCuUP l:150000
Signed-off-by: Zqiang <qiang.zhang@linux.dev>
---
kernel/rcu/tasks.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 6720dc25cd39..a146d1d98c22 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -723,6 +723,7 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
bool havecbs = false;
bool haveurgent = false;
bool haveurgentcbs = false;
+ bool havependtimer = false;
for_each_possible_cpu(cpu) {
struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
@@ -733,10 +734,12 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
haveurgent = true;
if (!data_race(rcu_segcblist_empty(&rtpcp->cblist)) && data_race(rtpcp->urgent_gp))
haveurgentcbs = true;
- if (havecbs && haveurgent && haveurgentcbs)
+ if (data_race(timer_pending(&rtpcp->lazy_timer)))
+ havependtimer = true;
+ if (havecbs && haveurgent && haveurgentcbs && havependtimer)
break;
}
- pr_info("%s: %s(%d) since %lu g:%lu i:%lu %c%c%c%c l:%lu %s\n",
+ pr_info("%s: %s(%d) since %lu g:%lu i:%lu %c%c%c%c%c l:%lu %s\n",
rtp->kname,
tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
jiffies - data_race(rtp->gp_jiffies),
@@ -746,6 +749,7 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
".C"[havecbs],
".u"[haveurgent],
".U"[haveurgentcbs],
+ ".P"[havependtimer],
rtp->lazy_jiffies,
s);
}
--
2.17.1
reply other threads:[~2026-07-16 9:58 UTC|newest]
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