From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0325A298CA5 for ; Fri, 9 Oct 2026 10:07:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791540475; cv=none; b=MrAQiRInxQiQYC5be7r4chIEyjPH/KQjwDjO4LX/L4oy7ONiACJvE8ITK4jhf5WceCLeldLbmV3ZJArsfWvVLZfW8T20bBVSrEQADPMzKrrEIrV2I255VG3NpUw/xqvDXt6eOUXzwsu3gtlFyWFqPTRb4wtYIWPDcrFASOt1CqI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791540475; c=relaxed/simple; bh=H2pso/1jAKRy8QRPb4tMmjjGjmDL0+cZxHY8Cl6wvP0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Slt4K3V2hGxMhsQvQ0oKUwbTvikHMJF520Sd3YQ7ACtqZTH1PS+rsVHGVPgt1/byS0oBC3U1Vcm1WiBHKI8l0C5HCZOiOMkpcxNIzBrZoIqHTvIsICM510x670M2YIzGvOA4c8ob4s/7evo39424pRX0/lJw4Q4XT80eumf3S5g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=In3kowbK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="In3kowbK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76BAC1F00899; Fri, 9 Oct 2026 10:07:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791540474; bh=pfHxhycY4c003LsMRsPy6F6Xh21xTwGQzv/lLDaJzCU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=In3kowbKxzi0zjMZuqzN80/iyK437ZerWuTZkRHz6Jyik7ekEn2cYLzTUoak3EWUd EjfkFJ9ZOzenPO/lmMhvKJlvq/Y/0tTyuLIUpaDWbf7hyWs5QacL9fDRzeZ1zkz3hq ClDcSUsA8cXXojGHySxdI7B0GCzCAkrjl2HDjG3zVCKGh6kQASybloEz4+HIcI3iw7 8XzvEmG96MXY5TFBzKR7YEklflWXQiN+gIQZc9AdIBRpjRL3ig+Ih1OC0NERgxZvK6 hSID8wHl5AQPNENRKy4yvp7Jo83XQuHjFY/r3TvDO+bHQdvRvoYs8+0ZUfwnAbMptz 9LhUT8gZ//h+g== From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Will Deacon , Thomas Gleixner , Ben Horgan , =?UTF-8?q?=C8=98tefania=20Ion?= , Catalin Marinas , Pankaj Patil , Borislav Petkov , Lorenzo Pieralisi , Jinjie Ruan , Mark Rutland , Tarun Sahu , Fuad Tabba , David Woodhouse , Peter Zijlstra , Marc Zyngier Subject: [PATCH v2 02/23] cpu/hotplug: Avoid trying to bring up CPUs that are already online Date: Fri, 9 Oct 2026 11:07:13 +0100 Message-ID: <20261009100738.31288-3-will@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261009100738.31288-1-will@kernel.org> References: <20261009100738.31288-1-will@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit There's little point trying to bring up a CPU that is already online. Although _cpu_up() handles this case by doing nothing (because the target state has already been reached), it's wasted effort when we can easily elide the call to cpu_up() in the first place. Check that the target CPU isn't already online before invoking cpu_up() from cpuhp_bringup_mask(). Reviewed-by: Jinjie Ruan Signed-off-by: Will Deacon --- kernel/cpu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 198c929c452a..97a9bfe4edad 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1769,7 +1769,8 @@ static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int n for_each_cpu(cpu, mask) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); - if (cpu_up(cpu, target) && can_rollback_cpu(st)) { + if (!cpu_online(cpu) && cpu_up(cpu, target) && + can_rollback_cpu(st)) { /* * If this failed then cpu_up() might have only * rolled back to CPUHP_BP_KICK_AP for the final -- 2.56.0.385.gd3acb90ef8-goog