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>,
Martin Lau <kafai@fb.com>,
Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Subject: [PATCH rcu 04/18] rcu-tasks: Convert grace-period counter to grace-period sequence number
Date: Wed, 1 Dec 2021 16:38:44 -0800 [thread overview]
Message-ID: <20211202003858.3129628-4-paulmck@kernel.org> (raw)
In-Reply-To: <20211202003826.GA3129369@paulmck-ThinkPad-P17-Gen-1>
This commit moves the rcu_tasks structure's ->n_gps grace-period-counter
field to a ->task_gp_seq grce-period sequence number in order to enable
use of the rcu_segcblist structure for the callback lists. This in turn
permits CPUs to lag behind the RCU Tasks grace-period sequence number
without suffering long-term slowdowns in callback invocation.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 2a5fe3e04b363..ed84d59b6dbfa 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -42,7 +42,7 @@ struct rcu_tasks_percpu {
* @init_fract: Initial backoff sleep interval.
* @gp_jiffies: Time of last @gp_state transition.
* @gp_start: Most recent grace-period start in jiffies.
- * @n_gps: Number of grace periods completed since boot.
+ * @tasks_gp_seq: Number of grace periods completed since boot.
* @n_ipis: Number of IPIs sent to encourage grace periods to end.
* @n_ipis_fails: Number of IPI-send failures.
* @pregp_func: This flavor's pre-grace-period function (optional).
@@ -64,7 +64,7 @@ struct rcu_tasks {
int init_fract;
unsigned long gp_jiffies;
unsigned long gp_start;
- unsigned long n_gps;
+ unsigned long tasks_gp_seq;
unsigned long n_ipis;
unsigned long n_ipis_fails;
struct task_struct *kthread_ptr;
@@ -273,8 +273,9 @@ static int __noreturn rcu_tasks_kthread(void *arg)
// Wait for one grace period.
set_tasks_gp_state(rtp, RTGS_WAIT_GP);
rtp->gp_start = jiffies;
+ rcu_seq_start(&rtp->tasks_gp_seq);
rtp->gp_func(rtp);
- rtp->n_gps++;
+ rcu_seq_end(&rtp->tasks_gp_seq);
/* Invoke the callbacks. */
set_tasks_gp_state(rtp, RTGS_INVOKE_CBS);
@@ -335,7 +336,7 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
rtp->kname,
tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
jiffies - data_race(rtp->gp_jiffies),
- data_race(rtp->n_gps),
+ data_race(rcu_seq_current(&rtp->tasks_gp_seq)),
data_race(rtp->n_ipis_fails), data_race(rtp->n_ipis),
".k"[!!data_race(rtp->kthread_ptr)],
".C"[!!data_race(rtpcp->cbs_head)],
--
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 ` [PATCH rcu 01/18] rcu-tasks: Don't remove tasks with pending IPIs from holdout list Paul E. McKenney
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 ` Paul E. McKenney [this message]
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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