| Message ID | 20201206235919.393158-5-vladimir.oltean@nxp.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Make .ndo_get_stats64 sleepable | expand |
| 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/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 |
diff --git a/arch/s390/appldata/appldata_net_sum.c b/arch/s390/appldata/appldata_net_sum.c index 59c282ca002f..27e9cc998d4d 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) { + mutex_lock(&init_net.netdev_lists_lock); + + 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(); + + mutex_unlock(&init_net.netdev_lists_unlock); net_data->nr_interfaces = i; net_data->rx_packets = rx_packets;
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> --- arch/s390/appldata/appldata_net_sum.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)