From nobody Thu Oct 2 15:16:47 2025 Received: from mail-pj1-f49.google.com (mail-pj1-f49.google.com [209.85.216.49]) (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 C8FD92E424F for ; Tue, 16 Sep 2025 04:49:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.49 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757998150; cv=none; b=mEWveKhf4QBNPQ/0cSnmLIAU6awaID0T33kBZPlpBqN7+/LrWVVBQPDCirtVWYoZ44Gn5pf6j1A1/YKQLbM9dONn5t3X2ixmZ6jtZ7Gup0KjpUe0QCy9gySDd3SGE5ll6m7kqqRRue2ZPpyvPpdnYw64YzTfcLLUmTGCmln42rU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757998150; c=relaxed/simple; bh=A1DaGpRAAYNdE/JnkBcpbGGz1TWyQSRA1+c5fRETaCo=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Z2mWvMni9phuqD23cmDtaKLfeTNH1bH1XPFEfT7P1FE9aEEP6uPBI6lGIZtp2/ZxB1Ghshom0Z4oe+wlPHGTulv9m8YmsdW9S4GdQke2S50Oe5oATTn09JRU+NC9VAZGwjzIymb04d/BjDtl4G1oM+CQtUIGmbHh1dzNyFNI2Kw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=K4Xjumc0; arc=none smtp.client-ip=209.85.216.49 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="K4Xjumc0" Received: by mail-pj1-f49.google.com with SMTP id 98e67ed59e1d1-32e715cbad3so1613755a91.3 for ; Mon, 15 Sep 2025 21:49:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1757998147; x=1758602947; 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=Gp+N7RFYdL+M8U5Aod5ZJl4PoDAFL89oD30EaW4MsNY=; b=K4Xjumc0nBcco5KyK7TayYg1GVB3J8fMW7YfmCjhgTTUc/fPIDKia1bI2dpOo4Dlpx o0oYiCFoIl/qnLukCt0JaKCTycIs9+9f38sOAgldyz8tQIGpDGM4I5xSF1yz9foe5Y+0 2p4TuTz/xI8E76jU6e6NUTzqr4tF4KFkj0cyt03nQJvtbqEvTMv5/6XrYgnXmNQLeb+O sDFNMQP/6B3RWiK8Q1KWu4oWPdcxqbwd7gQ0AyvjLj19qMjmrrjdeeVtI4h+aCXWk442 XnCfLw3QPsQeRmrhv0yiLaCyo05omJolYFv4x6BgsEMJUeoyH1rHSkFxKz1mCDro3W3Y TL4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757998147; x=1758602947; 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=Gp+N7RFYdL+M8U5Aod5ZJl4PoDAFL89oD30EaW4MsNY=; b=ieoLftJpVzWxtaxEQiYomFBuzfjR3KyHd16HnZCOfi3jJyydJ0/2STzqLREKGBbAG6 OmaIFDZK737Vv2bJ3bZg/JEdZwQzPnJ5kLgTywTvLVGvjmwTkah+0lSAu44j6IOdTYI6 KyA/+YuMagaERapdvRbMmoffe6rB8zgK+jSyWYuQtRDVT2wyx+OP8N+081I+S26FeTkt JrKAjVEUm6XwYx9qhShRVC7xnmCnO7VfSFPPHpjM7ECA6inTW/Oonc+8eJ8DB/ptnpJL u7S73jEgw+DJRkb5Zk0YaydpW+JXagGvb5S0pElrl8ZYs9UDTzdUgDcZ+nTJUqMBao32 ZmIg== X-Forwarded-Encrypted: i=1; AJvYcCUCgY27b8huNnq+qjKxEPY62YkaHMMzaSQaFsHjmh9eZmv6lqxtuHlO+JJgtBSxAbzEG55FQTolXIRINsg=@vger.kernel.org X-Gm-Message-State: AOJu0YwBR1p5fmsAhxvmgpok+yDj5qrk8O35h43R68SRyITd+um57P7O JD8gGY8Itnc95mMEMKhAPFQwEUbIP7A0m8uQ+H1yJWy5sqLD7/ECguo5 X-Gm-Gg: ASbGnctAGt6GhV2DBMTeMmbUlG5LXprDG92naa6mZLXQUE19zwqgDVl2MO8nG6jTHEm Sr6hRYsoj7ldQqPnlgPoBrElzRUHOLbpJALw+FBWAgrV++FzOZXnkS8dsSHe2Ch6Xa9aEhNVdxi 0AYJJeFootVLrvlpRrbeg2vKdtNbQQcYCDMpu/+VGhdzOD0QeJhRZ2q7x3GaEbHHzGNW/iFBKyb biENe0+DYbZKup/uK3eUP+epbR1gLKpe17sTWWcUNz1dY28gSU5sEqkZDL8OvfO12QOVBhMEZlP W2xqf2q82dGsMajT+ToI4wk5lFTWMVybQ7sEUBy7XCw52si0q5X4QDIzO9AWRdXQUORu+T7yquu G37E/ImkVt5MBguhCRhh7YsSnq9XwVF76yMahgH4= X-Google-Smtp-Source: AGHT+IFqD7sgMgos1nHHN1tffY5PC8RBagTW/SlAHYpHIH6iPNz9WSa7pJxkI6T7wvTsG+plknRS6A== X-Received: by 2002:a17:902:f70e:b0:266:120a:29c7 with SMTP id d9443c01a7336-266120a3078mr75581275ad.6.1757998147150; Mon, 15 Sep 2025 21:49:07 -0700 (PDT) Received: from pengdl-pc.mioffice.cn ([43.224.245.249]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-25ef09c77f8sm104600605ad.15.2025.09.15.21.49.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Sep 2025 21:49:06 -0700 (PDT) From: pengdonglin To: tj@kernel.org, tony.luck@intel.com, jani.nikula@linux.intel.com, ap420073@gmail.com, jv@jvosburgh.net, freude@linux.ibm.com, bcrl@kvack.org, trondmy@kernel.org, longman@redhat.com, kees@kernel.org Cc: bigeasy@linutronix.de, hdanton@sina.com, paulmck@kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-nfs@vger.kernel.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, netdev@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-wireless@vger.kernel.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, cgroups@vger.kernel.org, pengdonglin , Johannes Weiner , pengdonglin Subject: [PATCH v3 08/14] cgroup: Remove redundant rcu_read_lock/unlock() in spin_lock Date: Tue, 16 Sep 2025 12:47:29 +0800 Message-Id: <20250916044735.2316171-9-dolinux.peng@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250916044735.2316171-1-dolinux.peng@gmail.com> References: <20250916044735.2316171-1-dolinux.peng@gmail.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" From: pengdonglin Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side functio= n definitions") there is no difference between rcu_read_lock(), rcu_read_lock_bh() and rcu_read_lock_sched() in terms of RCU read section and the relevant grace period. That means that spin_lock(), which implies rcu_read_lock_sched(), also implies rcu_read_lock(). There is no need no explicitly start a RCU read section if one has already been started implicitly by spin_lock(). Simplify the code and remove the inner rcu_read_lock() invocation. Cc: Tejun Heo Cc: Johannes Weiner Cc: Waiman Long Signed-off-by: pengdonglin Signed-off-by: pengdonglin --- kernel/cgroup/cgroup.c | 2 -- kernel/cgroup/debug.c | 4 ---- 2 files changed, 6 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 312c6a8b55bb..db9e00a559df 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -2944,14 +2944,12 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, str= uct task_struct *leader, =20 /* look up all src csets */ spin_lock_irq(&css_set_lock); - rcu_read_lock(); task =3D leader; do { cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx); if (!threadgroup) break; } while_each_thread(leader, task); - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); =20 /* prepare dst csets and commit */ diff --git a/kernel/cgroup/debug.c b/kernel/cgroup/debug.c index 80aa3f027ac3..81ea38dd6f9d 100644 --- a/kernel/cgroup/debug.c +++ b/kernel/cgroup/debug.c @@ -49,7 +49,6 @@ static int current_css_set_read(struct seq_file *seq, voi= d *v) return -ENODEV; =20 spin_lock_irq(&css_set_lock); - rcu_read_lock(); cset =3D task_css_set(current); refcnt =3D refcount_read(&cset->refcount); seq_printf(seq, "css_set %pK %d", cset, refcnt); @@ -67,7 +66,6 @@ static int current_css_set_read(struct seq_file *seq, voi= d *v) seq_printf(seq, "%2d: %-4s\t- %p[%d]\n", ss->id, ss->name, css, css->id); } - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); cgroup_kn_unlock(of->kn); return 0; @@ -95,7 +93,6 @@ static int current_css_set_cg_links_read(struct seq_file = *seq, void *v) return -ENOMEM; =20 spin_lock_irq(&css_set_lock); - rcu_read_lock(); cset =3D task_css_set(current); list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { struct cgroup *c =3D link->cgrp; @@ -104,7 +101,6 @@ static int current_css_set_cg_links_read(struct seq_fil= e *seq, void *v) seq_printf(seq, "Root %d group %s\n", c->root->hierarchy_id, name_buf); } - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); kfree(name_buf); return 0; --=20 2.34.1