From: Peter Zijlstra <peterz@infradead.org>
To: tglx@linutronix.de, mingo@kernel.org
Cc: linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
qais.yousef@arm.com, swood@redhat.com, peterz@infradead.org,
valentin.schneider@arm.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vincent.donnefort@arm.com, tj@kernel.org,
ouwen210@hotmail.com
Subject: [PATCH v3 11/19] sched/core: Make migrate disable and CPU hotplug cooperative
Date: Thu, 15 Oct 2020 13:05:43 +0200 [thread overview]
Message-ID: <20201015110923.971283427@infradead.org> (raw)
In-Reply-To: 20201015110532.738127234@infradead.org
From: Thomas Gleixner <tglx@linutronix.de>
On CPU unplug tasks which are in a migrate disabled region cannot be pushed
to a different CPU until they returned to migrateable state.
Account the number of tasks on a runqueue which are in a migrate disabled
section and make the hotplug wait mechanism respect that.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/core.c | 36 ++++++++++++++++++++++++++++++------
kernel/sched/sched.h | 4 ++++
2 files changed, 34 insertions(+), 6 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1725,10 +1725,17 @@ static void migrate_disable_switch(struc
void migrate_disable(void)
{
- if (current->migration_disabled++)
+ struct task_struct *p = current;
+
+ if (p->migration_disabled) {
+ p->migration_disabled++;
return;
+ }
- barrier();
+ preempt_disable();
+ this_rq()->nr_pinned++;
+ p->migration_disabled = 1;
+ preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_disable);
@@ -1755,6 +1762,7 @@ void migrate_enable(void)
*/
barrier();
p->migration_disabled = 0;
+ this_rq()->nr_pinned--;
preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_enable);
@@ -1764,6 +1772,11 @@ static inline bool is_migration_disabled
return p->migration_disabled;
}
+static inline bool rq_has_pinned_tasks(struct rq *rq)
+{
+ return rq->nr_pinned;
+}
+
#endif
/*
@@ -2634,6 +2647,11 @@ static inline bool is_migration_disabled
return false;
}
+static inline bool rq_has_pinned_tasks(struct rq *rq)
+{
+ return false;
+}
+
#endif
static void
@@ -7006,15 +7024,20 @@ static bool balance_push(struct rq *rq)
* Both the cpu-hotplug and stop task are in this case and are
* required to complete the hotplug process.
*/
- if (is_per_cpu_kthread(push_task)) {
+ if (is_per_cpu_kthread(push_task) || is_migration_disabled(push_task)) {
/*
* If this is the idle task on the outgoing CPU try to wake
* up the hotplug control thread which might wait for the
* last task to vanish. The rcuwait_active() check is
* accurate here because the waiter is pinned on this CPU
* and can't obviously be running in parallel.
+ *
+ * On RT kernels this also has to check whether there are
+ * pinned and scheduled out tasks on the runqueue. They
+ * need to leave the migrate disabled section first.
*/
- if (!rq->nr_running && rcuwait_active(&rq->hotplug_wait)) {
+ if (!rq->nr_running && !rq_has_pinned_tasks(rq) &&
+ rcuwait_active(&rq->hotplug_wait)) {
raw_spin_unlock(&rq->lock);
rcuwait_wake_up(&rq->hotplug_wait);
raw_spin_lock(&rq->lock);
@@ -7063,7 +7086,8 @@ static void balance_hotplug_wait(void)
{
struct rq *rq = this_rq();
- rcuwait_wait_event(&rq->hotplug_wait, rq->nr_running == 1,
+ rcuwait_wait_event(&rq->hotplug_wait,
+ rq->nr_running == 1 && !rq_has_pinned_tasks(rq),
TASK_UNINTERRUPTIBLE);
}
@@ -7310,7 +7334,7 @@ int sched_cpu_dying(unsigned int cpu)
sched_tick_stop(cpu);
rq_lock_irqsave(rq, &rf);
- BUG_ON(rq->nr_running != 1);
+ BUG_ON(rq->nr_running != 1 || rq_has_pinned_tasks(rq));
rq_unlock_irqrestore(rq, &rf);
calc_load_migrate(rq);
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1053,6 +1053,10 @@ struct rq {
/* Must be inspected within a rcu lock section */
struct cpuidle_state *idle_state;
#endif
+
+#if defined(CONFIG_PREEMPT_RT) && defined(CONFIG_SMP)
+ unsigned int nr_pinned;
+#endif
};
#ifdef CONFIG_FAIR_GROUP_SCHED
next prev parent reply other threads:[~2020-10-15 11:09 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 11:05 [PATCH v3 00/19] sched: Migrate disable support Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 01/19] stop_machine: Add function and caller debug info Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 02/19] sched: Fix balance_callback() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 03/19] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 04/19] sched/core: Wait for tasks being pushed away on hotplug Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 05/19] workqueue: Manually break affinity " Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 06/19] sched/hotplug: Consolidate task migration on CPU unplug Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 07/19] sched: Fix hotplug vs CPU bandwidth control Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 08/19] sched: Massage set_cpus_allowed() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 09/19] sched: Add migrate_disable() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 10/19] sched: Fix migrate_disable() vs set_cpus_allowed_ptr() Peter Zijlstra
2020-10-15 13:54 ` Valentin Schneider
2020-10-15 14:19 ` Peter Zijlstra
2020-10-16 12:48 ` Valentin Schneider
[not found] ` <BN8PR12MB29784D239007D0D6CA3F4F2A9A010@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-18 15:51 ` Valentin Schneider
[not found] ` <BN8PR12MB2978F76887133CCA2102B7589A1E0@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-19 17:36 ` Valentin Schneider
[not found] ` <BN8PR12MB2978D36FF4A81C344DCF37FD9A1F0@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-20 7:56 ` Peter Zijlstra
2020-10-15 11:05 ` Peter Zijlstra [this message]
[not found] ` <BN8PR12MB2978A3BB8062DF4CEEB184109A030@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-16 9:35 ` [PATCH v3 11/19] sched/core: Make migrate disable and CPU hotplug cooperative Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 12/19] sched,rt: Use cpumask_any*_distribute() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 13/19] sched,rt: Use the full cpumask for balancing Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 14/19] sched, lockdep: Annotate ->pi_lock recursion Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 15/19] sched: Fix migrate_disable() vs rt/dl balancing Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 16/19] sched/proc: Print accurate cpumask vs migrate_disable() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 17/19] sched: Add migrate_disable() tracepoints Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 18/19] sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 19/19] sched: Comment affine_move_task() Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201015110923.971283427@infradead.org \
--to=peterz@infradead.org \
--cc=bigeasy@linutronix.de \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@kernel.org \
--cc=ouwen210@hotmail.com \
--cc=qais.yousef@arm.com \
--cc=rostedt@goodmis.org \
--cc=swood@redhat.com \
--cc=tglx@linutronix.de \
--cc=tj@kernel.org \
--cc=valentin.schneider@arm.com \
--cc=vincent.donnefort@arm.com \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).