On Thu, Jul 16, 2026 at 05:57:54PM +0800, Zqiang wrote:
> 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 <[email protected]>
Nice! Queued for review and testing, thank you!
Thanx, Paul
> ---
> 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
>
>
