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rcu-tasks: Dump rtpcp->lazy_timer status in show_rcu_tasks_generic_gp_kthread()

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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>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Zqiang 2026-07-16 17:57:54 +08:00 committed by Paul E. McKenney
parent 5976694882
commit 7a455d3cae
1 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/rcu/tasks.h
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@ -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);
}