From ffcc21a315e1ebafad51b318e8ac0cb884df0cdc Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 1 Jun 2022 21:26:57 -0700 Subject: [PATCH] rcu-tasks: Maintain a count of tasks blocking RCU Tasks Trace grace period This commit maintains a new n_trc_holdouts counter that tracks the number of tasks blocking the RCU Tasks grace period. This counter is useful for debugging, and its value has been added to a diagostic message. Signed-off-by: Paul E. McKenney Cc: Neeraj Upadhyay Cc: Eric Dumazet Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: KP Singh --- kernel/rcu/tasks.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index fe0552086ccf..9d7d6fd4b8a7 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -1206,6 +1206,7 @@ static DEFINE_PER_CPU(bool, trc_ipi_to_cpu); static unsigned long n_heavy_reader_attempts; static unsigned long n_heavy_reader_updates; static unsigned long n_heavy_reader_ofl_updates; +static unsigned long n_trc_holdouts; void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace, @@ -1299,6 +1300,7 @@ static void trc_add_holdout(struct task_struct *t, struct list_head *bhp) if (list_empty(&t->trc_holdout_list)) { get_task_struct(t); list_add(&t->trc_holdout_list, bhp); + n_trc_holdouts++; } } @@ -1308,6 +1310,7 @@ static void trc_del_holdout(struct task_struct *t) if (!list_empty(&t->trc_holdout_list)) { list_del_init(&t->trc_holdout_list); put_task_struct(t); + n_trc_holdouts--; } } @@ -1760,7 +1763,8 @@ void show_rcu_tasks_trace_gp_kthread(void) { char buf[64]; - sprintf(buf, "h:%lu/%lu/%lu", + sprintf(buf, "N%lu h:%lu/%lu/%lu", + data_race(n_trc_holdouts), data_race(n_heavy_reader_ofl_updates), data_race(n_heavy_reader_updates), data_race(n_heavy_reader_attempts)); -- 2.20.1