From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Vladimir Oltean Subject: [RFC PATCH v2 net-next 11/12] net: mark ndo_get_stats64 as being able to sleep Date: Tue, 5 Jan 2021 20:59:01 +0200 Message-Id: <20210105185902.3922928-12-olteanv@gmail.com> In-Reply-To: <20210105185902.3922928-1-olteanv@gmail.com> References: <20210105185902.3922928-1-olteanv@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit List-ID: To: "David S . Miller" , Jakub Kicinski Cc: netdev@vger.kernel.org, Andrew Lunn , Florian Fainelli , Paul Gortmaker , Pablo Neira Ayuso , Jiri Benc , Cong Wang , Jamal Hadi Salim , Stephen Hemminger , Eric Dumazet , George McCollister , Oleksij Rempel , Jay Vosburgh , Veaceslav Falico , Andy Gospodarek , Arnd Bergmann , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Taehee Yoo , Jiri Pirko , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Paolo Abeni , Christian Brauner , Florian Westphal , linux-s390@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-parisc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-usb@vger.kernel.org, dev@openvswitch.org From: Vladimir Oltean Now that all callers have been converted to not use atomic context when calling dev_get_stats, it is time to update the documentation and put a notice in the function that it expects process context. Signed-off-by: Vladimir Oltean --- Documentation/networking/netdevices.rst | 8 ++++++-- Documentation/networking/statistics.rst | 9 ++++----- net/core/dev.c | 2 ++ 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/Documentation/networking/netdevices.rst b/Documentation/networking/netdevices.rst index 5a85fcc80c76..944599722c76 100644 --- a/Documentation/networking/netdevices.rst +++ b/Documentation/networking/netdevices.rst @@ -64,8 +64,12 @@ ndo_do_ioctl: Context: process ndo_get_stats: - Synchronization: dev_base_lock rwlock. - Context: nominally process, but don't sleep inside an rwlock + Synchronization: + none. netif_lists_lock(net) might be held, but not guaranteed. + It is illegal to hold rtnl_lock() in this method, since it will + cause a lock inversion with netif_lists_lock and a deadlock. + Context: + process ndo_start_xmit: Synchronization: __netif_tx_lock spinlock. diff --git a/Documentation/networking/statistics.rst b/Documentation/networking/statistics.rst index 234abedc29b2..ad3e353df0dd 100644 --- a/Documentation/networking/statistics.rst +++ b/Documentation/networking/statistics.rst @@ -155,11 +155,10 @@ Drivers must ensure best possible compliance with Please note for example that detailed error statistics must be added into the general `rx_error` / `tx_error` counters. -The `.ndo_get_stats64` callback can not sleep because of accesses -via `/proc/net/dev`. If driver may sleep when retrieving the statistics -from the device it should do so periodically asynchronously and only return -a recent copy from `.ndo_get_stats64`. Ethtool interrupt coalescing interface -allows setting the frequency of refreshing statistics, if needed. +Drivers may sleep when retrieving the statistics from the device, or they might +read the counters periodically and only return in `.ndo_get_stats64` a recent +copy collected asynchronously. In the latter case, the ethtool interrupt +coalescing interface allows setting the frequency of refreshing statistics. Retrieving ethtool statistics is a multi-syscall process, drivers are advised to keep the number of statistics constant to avoid race conditions with diff --git a/net/core/dev.c b/net/core/dev.c index d48b75479b3e..6b7cdf8ab875 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10389,6 +10389,8 @@ void dev_get_stats(struct net_device *dev, struct rtnl_link_stats64 *storage) { const struct net_device_ops *ops = dev->netdev_ops; + might_sleep(); + if (ops->ndo_get_stats64) { memset(storage, 0, sizeof(*storage)); ops->ndo_get_stats64(dev, storage); -- 2.25.1