From nobody Wed Dec 17 21:54:43 2025 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B936A2EFDB6; Mon, 20 Oct 2025 22:09:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.97.179.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760998178; cv=none; b=AYFk48SsOHt/tlW0krZxyld4RyStwtC01h08eezroWrGovutLJv5xj8xDso1xwc4Gb0qSLcZQpkzS+lRZNTvXheMG8QCQi3M1FlFuBpmnYTnjujvs9bM/UJSwyoosixhSNTPGUniRniLGhmei9Dw5lCqbHOwLzd71CLoj4pSS9A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760998178; c=relaxed/simple; bh=MQxaliWFItSTzrB5ldB219NVZ2Hv1N/FY3RgMrK0rLs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hhshxXKmwqU9vH9Z14SJRjmhEoIQ9O+TvAAnG7b04Puz76QSAhS237T0Ax00TxxlKs4Nzk5EaWM5uemtBswtjN1wyNYEB9PlSRpAYEkw27N9JYk3pJSesocmFcwhqTsbOr5HuzUKQYspTxnp5Mk0si5plLcBj0eKfkfuuU6CJhQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=Zx9fh7s0; arc=none smtp.client-ip=213.97.179.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="Zx9fh7s0" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=exNZWDqT/nwVNJlHKkV/2gMvqE/a2tNWSKeiAf/i3rg=; b=Zx9fh7s0nTPlGWTIFxGlnAeiED m1BfNo67bIUSHwPJmuF9Gvvg3UI9EUb+biAwPd5Z9BeksHhfcebvbK21WQ03FqCJK4IeBxOyDlyN+ M9NzEe+qqwUC1YUuceJr4pVwFSHqUoYzdXcKVyTT5RNOb+ez2tiwoB4FQiiGblwxQcw8SR0PLgcGA KUufKm6rvwUJLt+xgUQx5jRK+J/o0yYdWipwKDcqyBY8i9D/LT9MXdEspOXqH8DyX6mqNuoD/B8e+ 56mZ5rkPNkxM1pYDsLtDQKHzAqkedI8uOXWJgcWSQXUK/dL/2JklZk4l5HEsaIEDCYci1TIt6GeDx fktmSFgQ==; Received: from [58.29.143.236] (helo=localhost) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1vAy4G-00CHWc-GD; Tue, 21 Oct 2025 00:09:29 +0200 From: Changwoo Min To: lukasz.luba@arm.com, rafael@kernel.org, len.brown@intel.com, pavel@kernel.org Cc: christian.loehle@arm.com, tj@kernel.org, kernel-dev@igalia.com, linux-pm@vger.kernel.org, sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org, Changwoo Min Subject: [PATCH v6 01/10] PM: EM: Assign a unique ID when creating a performance domain Date: Tue, 21 Oct 2025 07:09:05 +0900 Message-ID: <20251020220914.320832-2-changwoo@igalia.com> X-Mailer: git-send-email 2.51.1.dirty In-Reply-To: <20251020220914.320832-1-changwoo@igalia.com> References: <20251020220914.320832-1-changwoo@igalia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It is necessary to refer to a specific performance domain from a userspace. For example, the energy model of a particular performance domain is updated. To this end, assign a unique ID to each performance domain to address it, and manage them in a global linked list to look up a specific one by matching ID. IDA is used for ID assignment, and the mutex is used to protect the global list from concurrent access. Note that the mutex (em_pd_list_mutex) is not supposed to hold while holding em_pd_mutex to avoid ABBA deadlock. Signed-off-by: Changwoo Min --- include/linux/energy_model.h | 4 ++++ kernel/power/energy_model.c | 30 +++++++++++++++++++++++++++++- 2 files changed, 33 insertions(+), 1 deletion(-) diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h index 61d50571ad88..43aa6153dc57 100644 --- a/include/linux/energy_model.h +++ b/include/linux/energy_model.h @@ -54,6 +54,8 @@ struct em_perf_table { /** * struct em_perf_domain - Performance domain * @em_table: Pointer to the runtime modifiable em_perf_table + * @node: node in em_pd_list (in energy_model.c) + * @id: A unique ID number for each performance domain * @nr_perf_states: Number of performance states * @min_perf_state: Minimum allowed Performance State index * @max_perf_state: Maximum allowed Performance State index @@ -71,6 +73,8 @@ struct em_perf_table { */ struct em_perf_domain { struct em_perf_table __rcu *em_table; + struct list_head node; + int id; int nr_perf_states; int min_perf_state; int max_perf_state; diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c index 5f17d2e8e954..2047b546ad11 100644 --- a/kernel/power/energy_model.c +++ b/kernel/power/energy_model.c @@ -23,6 +23,16 @@ */ static DEFINE_MUTEX(em_pd_mutex); =20 +/* + * Manage performance domains with IDs. One can iterate the performance do= mains + * through the list and pick one with their associated ID. The mutex seria= lizes + * the list access. When holding em_pd_list_mutex, em_pd_mutex should not = be + * taken to avoid potential deadlock. + */ +static DEFINE_IDA(em_pd_ida); +static LIST_HEAD(em_pd_list); +static DEFINE_MUTEX(em_pd_list_mutex); + static void em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table); static void em_check_capacity_update(void); @@ -396,7 +406,7 @@ static int em_create_pd(struct device *dev, int nr_stat= es, struct em_perf_table *em_table; struct em_perf_domain *pd; struct device *cpu_dev; - int cpu, ret, num_cpus; + int cpu, ret, num_cpus, id; =20 if (_is_cpu_device(dev)) { num_cpus =3D cpumask_weight(cpus); @@ -420,6 +430,13 @@ static int em_create_pd(struct device *dev, int nr_sta= tes, =20 pd->nr_perf_states =3D nr_states; =20 + INIT_LIST_HEAD(&pd->node); + + id =3D ida_alloc(&em_pd_ida, GFP_KERNEL); + if (id < 0) + return -ENOMEM; + pd->id =3D id; + em_table =3D em_table_alloc(pd); if (!em_table) goto free_pd; @@ -444,6 +461,7 @@ static int em_create_pd(struct device *dev, int nr_stat= es, kfree(em_table); free_pd: kfree(pd); + ida_free(&em_pd_ida, id); return -EINVAL; } =20 @@ -660,6 +678,10 @@ int em_dev_register_pd_no_update(struct device *dev, u= nsigned int nr_states, unlock: mutex_unlock(&em_pd_mutex); =20 + mutex_lock(&em_pd_list_mutex); + list_add_tail(&dev->em_pd->node, &em_pd_list); + mutex_unlock(&em_pd_list_mutex); + return ret; } EXPORT_SYMBOL_GPL(em_dev_register_pd_no_update); @@ -678,6 +700,10 @@ void em_dev_unregister_perf_domain(struct device *dev) if (_is_cpu_device(dev)) return; =20 + mutex_lock(&em_pd_list_mutex); + list_del_init(&dev->em_pd->node); + mutex_unlock(&em_pd_list_mutex); + /* * The mutex separates all register/unregister requests and protects * from potential clean-up/setup issues in the debugfs directories. @@ -689,6 +715,8 @@ void em_dev_unregister_perf_domain(struct device *dev) em_table_free(rcu_dereference_protected(dev->em_pd->em_table, lockdep_is_held(&em_pd_mutex))); =20 + ida_free(&em_pd_ida, dev->em_pd->id); + kfree(dev->em_pd); dev->em_pd =3D NULL; mutex_unlock(&em_pd_mutex); --=20 2.51.1.dirty