From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH rcu 01/18] rcu-tasks: Don't remove tasks with pending IPIs from holdout list
Date: Wed, 1 Dec 2021 16:38:41 -0800 [thread overview]
Message-ID: <20211202003858.3129628-1-paulmck@kernel.org> (raw)
In-Reply-To: <20211202003826.GA3129369@paulmck-ThinkPad-P17-Gen-1>
Currently, the check_all_holdout_tasks_trace() function removes all tasks
marked with ->trc_reader_checked from the holdout list, including those
with IPIs pending. This means that the IPI handler might arrive at
a task that has already been removed from the list, which is at best
an accident waiting to happen.
This commit therefore avoids removing tasks with IPIs pending from
the holdout list. This in turn means that the "if" condition in the
for_each_online_cpu() loop in rcu_tasks_trace_postgp() should always
evaluate to false, so a WARN_ON_ONCE() is added to check that.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 7da3c81c3f59c..bd44cd4794d3d 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1121,7 +1121,8 @@ static void check_all_holdout_tasks_trace(struct list_head *hop,
trc_wait_for_one_reader(t, hop);
// If check succeeded, remove this task from the list.
- if (READ_ONCE(t->trc_reader_checked))
+ if (smp_load_acquire(&t->trc_ipi_to_cpu) == -1 &&
+ READ_ONCE(t->trc_reader_checked))
trc_del_holdout(t);
else if (needreport)
show_stalled_task_trace(t, firstreport);
@@ -1156,7 +1157,7 @@ static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp)
// Yes, this assumes that CPUs process IPIs in order. If that ever
// changes, there will need to be a recheck and/or timed wait.
for_each_online_cpu(cpu)
- if (smp_load_acquire(per_cpu_ptr(&trc_ipi_to_cpu, cpu)))
+ if (WARN_ON_ONCE(smp_load_acquire(per_cpu_ptr(&trc_ipi_to_cpu, cpu))))
smp_call_function_single(cpu, rcu_tasks_trace_empty_fn, NULL, 1);
// Remove the safety count.
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2021-12-02 0:39 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-02 0:38 [PATCH rcu 0/18] RCU Tasks updates for v5.17 Paul E. McKenney
2021-12-02 0:38 ` Paul E. McKenney [this message]
2021-12-02 0:38 ` [PATCH rcu 02/18] rcu-tasks: Create per-CPU callback lists Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 03/18] rcu-tasks: Introduce ->percpu_enqueue_shift for dynamic queue selection Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 04/18] rcu-tasks: Convert grace-period counter to grace-period sequence number Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 05/18] rcu_tasks: Convert bespoke callback list to rcu_segcblist structure Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 06/18] rcu-tasks: Use spin_lock_rcu_node() and friends Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 07/18] rcu-tasks: Inspect stalled task's trc state in locked state Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 08/18] rcu-tasks: Add a ->percpu_enqueue_lim to the rcu_tasks structure Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 09/18] rcu-tasks: Abstract checking of callback lists Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 10/18] rcu-tasks: Abstract invocations of callbacks Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 11/18] rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 12/18] rcu-tasks: Make rcu_barrier_tasks*() handle multiple callback queues Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 13/18] rcu-tasks: Add rcupdate.rcu_task_enqueue_lim to set initial queueing Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 14/18] rcu-tasks: Count trylocks to estimate call_rcu_tasks() contention Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 15/18] rcu-tasks: Avoid raw-spinlocked wakeups from call_rcu_tasks_generic() Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 16/18] rcu-tasks: Use more callback queues if contention encountered Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 17/18] rcu-tasks: Use separate ->percpu_dequeue_lim for callback dequeueing Paul E. McKenney
2021-12-02 0:38 ` [PATCH rcu 18/18] rcu-tasks: Use fewer callbacks queues if callback flood ends Paul E. McKenney
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