From: Valentin Schneider <valentin.schneider@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: tglx@linutronix.de, mingo@kernel.org,
linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
qais.yousef@arm.com, swood@redhat.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: Re: [PATCH v3 10/19] sched: Fix migrate_disable() vs set_cpus_allowed_ptr()
Date: Thu, 15 Oct 2020 14:54:53 +0100 [thread overview]
Message-ID: <jhjo8l3r3v6.mognet@arm.com> (raw)
In-Reply-To: <20201015110923.910090294@infradead.org>
On 15/10/20 12:05, Peter Zijlstra wrote:
> +static int affine_move_task(struct rq *rq, struct rq_flags *rf,
> + struct task_struct *p, int dest_cpu, unsigned int flags)
> +{
> + struct set_affinity_pending my_pending = { }, *pending = NULL;
> + struct migration_arg arg = {
> + .task = p,
> + .dest_cpu = dest_cpu,
> + };
> + bool complete = false;
> +
> + /* Can the task run on the task's current CPU? If so, we're done */
> + if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
> + pending = p->migration_pending;
> + if (pending) {
> + p->migration_pending = NULL;
> + complete = true;
Deciphering my TLA+ deadlock traces leads me to think this needs
refcount_inc(&pending->refs);
because the 'goto do_complete' leads us to an unconditional decrement.
> + }
> + task_rq_unlock(rq, p, rf);
> +
> + if (complete)
> + goto do_complete;
^^^^
that here
> +
> + return 0;
> + }
> +
[...]
> +do_complete:
> + if (complete)
> + complete_all(&pending->done);
> + }
> +
> + wait_for_completion(&pending->done);
> +
> + if (refcount_dec_and_test(&pending->refs))
^^^^^^^^^^^^^^^^^^^^^^^
leads to this guy there
> + wake_up_var(&pending->refs);
> +
> + wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));
> +
> + return 0;
> +}
next prev parent reply other threads:[~2020-10-15 13:55 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 [this message]
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 ` [PATCH v3 11/19] sched/core: Make migrate disable and CPU hotplug cooperative Peter Zijlstra
[not found] ` <BN8PR12MB2978A3BB8062DF4CEEB184109A030@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-16 9:35 ` 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
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