| Message ID | 20210824114049.3814660-6-vladimir.oltean@nxp.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Drop rtnl_lock from DSA .port_fdb_{add,del} | 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/cc_maintainers | warning | 5 maintainers not CCed: davem@davemloft.net linux-mediatek@lists.infradead.org kuba@kernel.org linux-arm-kernel@lists.infradead.org matthias.bgg@gmail.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, 14 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
diff --git a/net/dsa/slave.c b/net/dsa/slave.c index 662ff531d4e2..53394fb43d67 100644 --- a/net/dsa/slave.c +++ b/net/dsa/slave.c @@ -2381,7 +2381,6 @@ static void dsa_slave_switchdev_event_work(struct work_struct *work) dp = dsa_to_port(ds, switchdev_work->port); - rtnl_lock(); switch (switchdev_work->event) { case SWITCHDEV_FDB_ADD_TO_DEVICE: if (switchdev_work->host_addr) @@ -2416,7 +2415,6 @@ static void dsa_slave_switchdev_event_work(struct work_struct *work) break; } - rtnl_unlock(); dev_put(switchdev_work->dev); kfree(switchdev_work);
After talking with Ido Schimmel, it became clear that rtnl_lock is not actually required for anything that is done inside the SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE deferred work handlers. The reason why it was probably added by Arkadi Sharshevsky in commit c9eb3e0f8701 ("net: dsa: Add support for learning FDB through notification") was to offer the same locking/serialization guarantees as .ndo_fdb_{add,del} and avoid reworking any drivers. DSA has implemented .ndo_fdb_add and .ndo_fdb_del until commit b117e1e8a86d ("net: dsa: delete dsa_legacy_fdb_add and dsa_legacy_fdb_del") - that is to say, until fairly recently. But those methods have been deleted, so now we are free to drop the rtnl_lock as well. Note that exposing DSA switch drivers to an unlocked method which was previously serialized by the rtnl_mutex is a potentially dangerous affair. Driver writers couldn't ensure that their internal locking scheme does the right thing even if they wanted. We could err on the side of paranoia and introduce a switch-wide lock inside the DSA framework, but that seems way overreaching. Instead, we could check as many drivers for regressions as we can, fix those first, then let this change go in once it is assumed to be fairly safe. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> --- net/dsa/slave.c | 2 -- 1 file changed, 2 deletions(-)