diff mbox series

[v6,net-next,05/15] s390/appldata_net_sum: hold the netdev lists lock when retrieving device statistics

Message ID 20210109172624.2028156-6-olteanv@gmail.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series Make .ndo_get_stats64 sleepable | expand

Checks

Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for net-next
netdev/subject_prefix success Link
netdev/cc_maintainers fail 6 maintainers not CCed: hca@linux.ibm.com gerald.schaefer@linux.ibm.com borntraeger@de.ibm.com linux-s390@vger.kernel.org gor@linux.ibm.com vladimir.oltean@nxp.com
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 20 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success Link
netdev/stable success Stable not CCed

Commit Message

Vladimir Oltean Jan. 9, 2021, 5:26 p.m. UTC 
From: Vladimir Oltean <vladimir.oltean@nxp.com>

In the effort of making .ndo_get_stats64 be able to sleep, we need to
ensure the callers of dev_get_stats do not use atomic context.

In the case of the appldata driver, an RCU read-side critical section is
used to ensure the integrity of the list of network interfaces, because
the driver iterates through all net devices in the netns to aggregate
statistics. We still need some protection against an interface
registering or deregistering, and the writer-side lock, the netns's
mutex, is fine for that, because it offers sleepable context.

The ops->callback function is called from under appldata_ops_mutex
protection, so this is proof that the context is sleepable and holding
a mutex is therefore fine.

Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Changes in v6:
None.

Changes in v5:
None.

Changes in v4:
None.

Changes in v3:
None.

Changes in v2:
None.

 arch/s390/appldata/appldata_net_sum.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/s390/appldata/appldata_net_sum.c b/arch/s390/appldata/appldata_net_sum.c
index 59c282ca002f..4db886980cba 100644
--- a/arch/s390/appldata/appldata_net_sum.c
+++ b/arch/s390/appldata/appldata_net_sum.c
@@ -78,8 +78,9 @@  static void appldata_get_net_sum_data(void *data)
 	tx_dropped = 0;
 	collisions = 0;
 
-	rcu_read_lock();
-	for_each_netdev_rcu(&init_net, dev) {
+	netif_lists_lock(&init_net);
+
+	for_each_netdev(&init_net, dev) {
 		const struct rtnl_link_stats64 *stats;
 		struct rtnl_link_stats64 temp;
 
@@ -95,7 +96,8 @@  static void appldata_get_net_sum_data(void *data)
 		collisions += stats->collisions;
 		i++;
 	}
-	rcu_read_unlock();
+
+	netif_lists_unlock(&init_net);
 
 	net_data->nr_interfaces = i;
 	net_data->rx_packets = rx_packets;