[PATCH v6 net-next 15/15] net: mark ndo_get_stats64 as being able to sleep
From: Vladimir Oltean <olteanv@gmail.com>
Date: 2021-01-09 17:29:01
Subsystem:
documentation, networking [general], the rest · Maintainers:
Jonathan Corbet, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Vladimir Oltean <vladimir.oltean@nxp.com>
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 <vladimir.oltean@nxp.com>
---
Changes in v6:
Rebase on top of Jakub's patch 9f9d41f03bb0 ("docs: net: fix
documentation on .ndo_get_stats").
Changes in v5:
None.
Changes in v4:
None.
Changes in v3:
None.
Changes in v2:
Updated the documentation.
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 e65665c5ab50..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: rtnl_lock() semaphore, dev_base_lock rwlock, or RCU. - Context: atomic (can't sleep under rwlock or RCU) + 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 30facac95d5e..afd0e226efd4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -10409,6 +10409,8 @@ int __must_check dev_get_stats(struct net_device *dev, const struct net_device_ops *ops = dev->netdev_ops; int err = 0; + might_sleep(); + if (ops->ndo_get_stats64) { memset(storage, 0, sizeof(*storage)); err = ops->ndo_get_stats64(dev, storage);
--
2.25.1