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Wysocki" , Danilo Krummrich Subject: [PATCH 3/3] driver core: WQ_PERCPU added to alloc_workqueue users Date: Fri, 24 Oct 2025 12:19:04 +0200 Message-ID: <20251024101904.146351-4-marco.crivellari@suse.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251024101904.146351-1-marco.crivellari@suse.com> References: <20251024101904.146351-1-marco.crivellari@suse.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. alloc_workqueue() treats all queues as per-CPU by default, while unbound workqueues must opt-in via WQ_UNBOUND. This default is suboptimal: most workloads benefit from unbound queues, allowing the scheduler to place worker threads where they=E2=80=99re needed= and reducing noise when CPUs are isolated. This change adds a new WQ_PERCPU flag to explicitly request alloc_workqueue= () to be per-cpu when WQ_UNBOUND has not been specified. With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), any alloc_workqueue() caller that doesn=E2=80=99t explicitly specify WQ_UNB= OUND must now use WQ_PERCPU. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari --- drivers/base/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 3c533dab8fa5..4dd264207a82 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -4138,7 +4138,7 @@ int __init devices_init(void) sysfs_dev_char_kobj =3D kobject_create_and_add("char", dev_kobj); if (!sysfs_dev_char_kobj) goto char_kobj_err; - device_link_wq =3D alloc_workqueue("device_link_wq", 0, 0); + device_link_wq =3D alloc_workqueue("device_link_wq", WQ_PERCPU, 0); if (!device_link_wq) goto wq_err; =20 --=20 2.51.0