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Message-Id: <20241009125127.18902-6-neeraj.upadhyay@kernel.org> Date: Wed, 9 Oct 2024 18:21:22 +0530 From: neeraj.upadhyay@...nel.org To: rcu@...r.kernel.org Cc: linux-kernel@...r.kernel.org, paulmck@...nel.org, joel@...lfernandes.org, frederic@...nel.org, boqun.feng@...il.com, urezki@...il.com, rostedt@...dmis.org, mathieu.desnoyers@...icios.com, jiangshanlai@...il.com, qiang.zhang1211@...il.com, peterz@...radead.org, neeraj.upadhyay@....com, Neeraj Upadhyay <neeraj.upadhyay@...nel.org> Subject: [PATCH v2 05/10] rcu/tasks: Consider idle tasks not running on CPU as non-holdouts From: Neeraj Upadhyay <neeraj.upadhyay@...nel.org> As idle tasks cannot be non-voluntary preempted, idle tasks which are not running on CPU are not in RCU-tasks read side critical section. So, remove them for holdout tasks for RCU-tasks. Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@...nel.org> --- kernel/rcu/tasks.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index b794deeaf6d8..9523aff6cdae 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -983,6 +983,15 @@ static bool rcu_idle_task_is_holdout(struct task_struct *t, int cpu) if (!rcu_cpu_online(cpu)) return false; + /* + * As idle tasks cannot be involuntary preempted, non-running idle tasks + * are not in RCU-tasks critical section. + * synchronize_rcu() calls in rcu_tasks_pregp_step() and rcu_tasks_postgp() + * ensure that all ->on_cpu transitions are complete. + */ + if (!t->on_cpu) + return false; + return true; } #else /* #ifdef CONFIG_SMP */ -- 2.40.1
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