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Wysocki" , Danilo Krummrich Subject: [PATCH 1/3] driver core: replace use of system_unbound_wq with system_dfl_wq Date: Fri, 24 Oct 2025 12:19:02 +0200 Message-ID: <20251024101904.146351-2-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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. system_unbound_wq should be the default workqueue so as not to enforce locality constraints for random work whenever it's not required. Adding system_dfl_wq to encourage its use when unbound work should be used. The old system_unbound_wq will be kept for a few release cycles. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari --- drivers/base/dd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 13ab98e033ea..4938a132a085 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -193,7 +193,7 @@ void driver_deferred_probe_trigger(void) * Kick the re-probe thread. It may already be scheduled, but it is * safe to kick it again. */ - queue_work(system_unbound_wq, &deferred_probe_work); + queue_work(system_dfl_wq, &deferred_probe_work); } =20 /** --=20 2.51.0 From nobody Sat Feb 7 19:45:47 2026 Received: from mail-wr1-f47.google.com (mail-wr1-f47.google.com [209.85.221.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 878853081D0 for ; Fri, 24 Oct 2025 10:19:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.47 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761301162; cv=none; b=d6VULEMo1T6IgPyHNOIuZq6BeWuU4BG3pDpQyxJU3emR4pqnDvNvcDe3GvFDjIF+n+QD0eS+HrEGok0rDgxrbcgxAnIyEGda9sxyKzSDK5PUhnJLIkhxFjpvQMqqqwFCIdONCaPiTAKLNB3AY/AUED7/jyKvzmJDyHQzHM8BlJE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761301162; c=relaxed/simple; bh=Oi1ByVHeEu2zWSl2sH20SGmEO9NEsvJ+ngc0jBxXKMM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GywyzZcuU1yM+uNnoOu3CD3HSD+ffHaHoVAkIApQXNfpz89N3ThMo9vulbRk/EFpEJ6Y91X1h/5t0Fo+rTepaYS8njKvhZDf5bXgi8Gmu8Y2HVmhO1PCe0kt8WTudFnAr4u51uI8BOS/H8K2jeGHmlRh4R9QNAT6xM7ptuiQJQg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=ATC/7WXd; arc=none smtp.client-ip=209.85.221.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="ATC/7WXd" Received: by mail-wr1-f47.google.com with SMTP id ffacd0b85a97d-42420c7de22so906377f8f.1 for ; Fri, 24 Oct 2025 03:19:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1761301158; x=1761905958; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Hej3NvQOVSwgl8c1b8LmD8roMKr+o3O+e3J3aSquuOE=; b=ATC/7WXdkR9aeX3eD1Y5uuUup5vioboVcIM4znaid3M6GMBUL6Z3/WezTFXg8ChzZM EfsU8aAPFQKDqOIIMk/P0LE+3O4bWP+Ey4IBmExw2SwIZLqk49ETDoQKt76ZO3ro8dLG 4kZgLy0zKvkiUXdR12f+BRjSjk+S+aKTm6N3bSJv7mERgCiH/MJwm+E6U4BC63X8FDof 096ZqAn/ieOC3q0SxrE2Yl+XVvYU8/tb3Kp2RvMthLt9yyyLRX4eZUercZK7E3ouqt81 7xsEbFHO/v3oiKTn+f4uF5rI34PlqigdF/9gheomkNJMiK8C7SkYyml85MOXjTGKM4no DpSg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761301158; x=1761905958; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Hej3NvQOVSwgl8c1b8LmD8roMKr+o3O+e3J3aSquuOE=; b=EjVQEl2ybsgjqLR+QnH86lHocJYnjCfQoZBwHGe5px4kBaKuJybN0u70UagLaprL0f As4d9FfuWW+7sgqDhrSIkGNz9ov5vvLj81t/LEB5D6QNpM1qqKtoTiS2PkXzAk5HBmUw dJ3VJ/OlvkN1wwnzpt4rdw0+4teaSpi0+IUfxgya03S4Hw7clNImu5V742gV6jaJ5sWX huPFiVdL6ECJ9Hrq3O8AvZRJ9prSkH2TZUntb4el4P+gHApbIEEucMgPTYdTDuhaq5a3 7npc0fHYUU9E2KPLoVMA5D1XsS1kViXHXN7hYAWy7cz1AvKLD2dQ8VgkB3+Xqbfn5nAv lYFw== X-Gm-Message-State: AOJu0YwJqxMFqBC3L+gZQ+xiOuO/ckKRu14e+Z5SPdxdubuCgI3D6DfC M6h6bIQW6hr9UTrX9yjmjoq2T7zqIyERnr0jd3OXyBDlsfsK/QuQPQEYJmvcU1aM7I5jl6bXPVV 4c9Vc X-Gm-Gg: ASbGncsgWoT5lVezlkaUNNatdwp/R9qauRkiRMdPO+kM2low1HxEwgGJES1nwWvM7z0 7cRzVLRe2j1jaCCjoXp9I+n4R3JZtc90VbLLz8zZZtTLW5YPTqJgz1/79wVudZz8oIXC3A+dk2p A+YyV/Ezcxp5qxjbSdI8GjiPGHLo+LDGKdCb1KFql55o/6dJC2CEvqIl2gDXgIawqSfDGQqjUgy n9z0bcq0AOy+HnhCR2Xo0t8jSTZGZJWJk2UdHlHD8ynFtvBKMdt7vs4aPdQFZUHQ5maxRi1UDcj RzPTIYGQMxakWxGuLjQWkSGB09jgvLKvKEWsY3aUVskf0v5XQolVhK/b/jETJUUphVKHM/AnP+e BhgoY3Yve4Bhe0d+5YPOONQkQAR1hGEal85hkwO8yKcv2IR3SCMjkmqxGMrL8jw9gHe4cabyNn9 yo3iLCyuW3YsYG3vpJH+fXQTq5E8QTYh1FFC0= X-Google-Smtp-Source: AGHT+IEkJHkd+PPIVsbfRDip0CBU6v0MtBY4CPu9sZNoe9ovulbXyDrIMxugN4ezuaNuHNIvHPdX1w== X-Received: by 2002:a05:6000:2087:b0:429:66bf:1463 with SMTP id ffacd0b85a97d-42966bf1618mr4602739f8f.44.1761301158555; Fri, 24 Oct 2025 03:19:18 -0700 (PDT) Received: from localhost.localdomain ([2a00:6d43:105:c401:e307:1a37:2e76:ce91]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429897f52aasm8372695f8f.12.2025.10.24.03.19.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Oct 2025 03:19:18 -0700 (PDT) From: Marco Crivellari To: linux-kernel@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Marco Crivellari , Michal Hocko , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich Subject: [PATCH 2/3] devcoredump: replace use of system_wq with system_percpu_wq Date: Fri, 24 Oct 2025 12:19:03 +0200 Message-ID: <20251024101904.146351-3-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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. system_wq should be the per-cpu workqueue, yet in this name nothing makes that clear, so replace system_wq with system_percpu_wq. The old wq (system_wq) will be kept for a few release cycles. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari --- drivers/base/devcoredump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c index 37faf6156d7c..9596a27d00ce 100644 --- a/drivers/base/devcoredump.c +++ b/drivers/base/devcoredump.c @@ -125,7 +125,7 @@ static ssize_t devcd_data_write(struct file *filp, stru= ct kobject *kobj, mutex_lock(&devcd->mutex); if (!devcd->delete_work) { devcd->delete_work =3D true; - mod_delayed_work(system_wq, &devcd->del_wk, 0); + mod_delayed_work(system_percpu_wq, &devcd->del_wk, 0); } mutex_unlock(&devcd->mutex); =20 --=20 2.51.0 From nobody Sat Feb 7 19:45:47 2026 Received: from mail-wr1-f45.google.com (mail-wr1-f45.google.com [209.85.221.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C68630F80D for ; Fri, 24 Oct 2025 10:19:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Fri, 24 Oct 2025 03:19:19 -0700 (PDT) Received: from localhost.localdomain ([2a00:6d43:105:c401:e307:1a37:2e76:ce91]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429897f52aasm8372695f8f.12.2025.10.24.03.19.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Oct 2025 03:19:19 -0700 (PDT) From: Marco Crivellari To: linux-kernel@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Marco Crivellari , Michal Hocko , Greg Kroah-Hartman , "Rafael J . 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