From patchwork Wed Jan 15 03:53:10 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Kicinski X-Patchwork-Id: 13939814 X-Patchwork-Delegate: kuba@kernel.org Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B06A322E3F4 for ; Wed, 15 Jan 2025 03:53:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736913218; cv=none; b=Y5rbqMG5QL0HgTP6RhpuDcc0/f6AmCcC3YUP3BZcNS6ar6ppUmkdZ4egyfnDIJzufpuTOb5WeOrZ7hEPUreJO2hRTb4wwALpgaRONWzdh/MMoqhn92zC0atODTDd/akTV11f0qtMjUTfMKzqV8pns0y5N/OJPrF21xWGfj6RKUk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736913218; c=relaxed/simple; bh=9JEyl5sdkje6p3P7Kzrigfid34QwP8UKD23Ziugmw+Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uos6hf9MWOxpD+gTy2pSMwcvR4cNWa5wfwZrwzN+8+YKOMOzP9ewuqad1CC/+//+GAFlcOKp5V8ozcrLgzlRk279aWRp+KfN5Q4NTIYuC9ecFP+n7kGbJk54Q9bu2qg324dVH6VKMJLKgedWJyhXoFHsIJqGJ4cxIWMRjOH31ew= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YRy8UV3z; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YRy8UV3z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D884EC4CEE2; Wed, 15 Jan 2025 03:53:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736913218; bh=9JEyl5sdkje6p3P7Kzrigfid34QwP8UKD23Ziugmw+Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YRy8UV3z05haUCU97iJrfkf4zuCXmtZw43P7TL2AcmGzqgrfJlVxTk35n+FXdFbjd HO5MZ6qVqTj5IpKAe0WvcG5z9qqaDEBZ46wPrYqRQjZLJMrHqu11jfutzrQ3arJsXI a9VWr+G2qNJQEJvXGav8L3mbZhHI3h1FwggV4HxXAEegh4B/WkuIbCWDd0GSCzj+hw zC01M6ECX6Hb7oUG+rgfAOlbVeJXcnAOvDepu11se106j3FIFU5l/96ePH/r7z3CZx mxFTDb2FQoFldms6gFu6iBfAxraepvUXh8pMhUlnZkagWMTBWltmqOHSB0F87feLrU XTQzl0v/70XHg== From: Jakub Kicinski To: davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, jdamato@fastly.com, Jakub Kicinski Subject: [PATCH net-next v2 02/11] net: make netdev_lock() protect netdev->reg_state Date: Tue, 14 Jan 2025 19:53:10 -0800 Message-ID: <20250115035319.559603-3-kuba@kernel.org> X-Mailer: git-send-email 2.48.0 In-Reply-To: <20250115035319.559603-1-kuba@kernel.org> References: <20250115035319.559603-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org Protect writes to netdev->reg_state with netdev_lock(). From now on holding netdev_lock() is sufficient to prevent the net_device from getting unregistered, so code which wants to hold just a single netdev around no longer needs to hold rtnl_lock. We do not protect the NETREG_UNREGISTERED -> NETREG_RELEASED transition. We'd need to move mutex_destroy(netdev->lock) to .release, but the real reason is that trying to stop the unregistration process mid-way would be unsafe / crazy. Taking references on such devices is not safe, either. So the intended semantics are to lock REGISTERED devices. Reviewed-by: Joe Damato Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski Reviewed-by: Kuniyuki Iwashima --- v2: - reorder with next patch v1: https://lore.kernel.org/20250114035118.110297-4-kuba@kernel.org --- include/linux/netdevice.h | 2 +- net/core/dev.c | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 891c5bdb894c..30963c5d409b 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2448,7 +2448,7 @@ struct net_device { * Should always be taken using netdev_lock() / netdev_unlock() helpers. * Drivers are free to use it for other protection. * - * Protects: @net_shaper_hierarchy. + * Protects: @reg_state, @net_shaper_hierarchy. * Ordering: take after rtnl_lock. */ struct mutex lock; diff --git a/net/core/dev.c b/net/core/dev.c index fda4e1039bf0..6603c08768f6 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10668,7 +10668,9 @@ int register_netdevice(struct net_device *dev) ret = netdev_register_kobject(dev); + netdev_lock(dev); WRITE_ONCE(dev->reg_state, ret ? NETREG_UNREGISTERED : NETREG_REGISTERED); + netdev_unlock(dev); if (ret) goto err_uninit_notify; @@ -10942,7 +10944,9 @@ void netdev_run_todo(void) continue; } + netdev_lock(dev); WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED); + netdev_unlock(dev); linkwatch_sync_dev(dev); } @@ -11548,7 +11552,9 @@ void unregister_netdevice_many_notify(struct list_head *head, list_for_each_entry(dev, head, unreg_list) { /* And unlink it from device chain. */ unlist_netdevice(dev); + netdev_lock(dev); WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING); + netdev_unlock(dev); } flush_all_backlogs();