| Message ID | 20210824114049.3814660-3-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, 49 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
diff --git a/drivers/net/dsa/sja1105/sja1105.h b/drivers/net/dsa/sja1105/sja1105.h index 2e899c9f036d..78624851d1f8 100644 --- a/drivers/net/dsa/sja1105/sja1105.h +++ b/drivers/net/dsa/sja1105/sja1105.h @@ -248,6 +248,8 @@ struct sja1105_private { * the switch doesn't confuse them with one another. */ struct mutex mgmt_lock; + /* Serializes access to the dynamic config interface */ + struct mutex dynamic_config_lock; struct devlink_region **regions; struct sja1105_cbs_entry *cbs; struct mii_bus *mdio_base_t1; diff --git a/drivers/net/dsa/sja1105/sja1105_dynamic_config.c b/drivers/net/dsa/sja1105/sja1105_dynamic_config.c index 32ec34f181de..7729d3f8b7f5 100644 --- a/drivers/net/dsa/sja1105/sja1105_dynamic_config.c +++ b/drivers/net/dsa/sja1105/sja1105_dynamic_config.c @@ -1283,12 +1283,16 @@ int sja1105_dynamic_config_read(struct sja1105_private *priv, ops->entry_packing(packed_buf, entry, PACK); /* Send SPI write operation: read config table entry */ + mutex_lock(&priv->dynamic_config_lock); rc = sja1105_xfer_buf(priv, SPI_WRITE, ops->addr, packed_buf, ops->packed_size); - if (rc < 0) + if (rc < 0) { + mutex_unlock(&priv->dynamic_config_lock); return rc; + } rc = sja1105_dynamic_config_wait_complete(priv, &cmd, ops); + mutex_unlock(&priv->dynamic_config_lock); if (rc < 0) return rc; @@ -1349,12 +1353,16 @@ int sja1105_dynamic_config_write(struct sja1105_private *priv, ops->entry_packing(packed_buf, entry, PACK); /* Send SPI write operation: read config table entry */ + mutex_lock(&priv->dynamic_config_lock); rc = sja1105_xfer_buf(priv, SPI_WRITE, ops->addr, packed_buf, ops->packed_size); - if (rc < 0) + if (rc < 0) { + mutex_unlock(&priv->dynamic_config_lock); return rc; + } rc = sja1105_dynamic_config_wait_complete(priv, &cmd, ops); + mutex_unlock(&priv->dynamic_config_lock); if (rc < 0) return rc; diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c index 05ba65042b5f..dbfbb949a485 100644 --- a/drivers/net/dsa/sja1105/sja1105_main.c +++ b/drivers/net/dsa/sja1105/sja1105_main.c @@ -3285,6 +3285,7 @@ static int sja1105_probe(struct spi_device *spi) priv->ds = ds; mutex_init(&priv->ptp_data.lock); + mutex_init(&priv->dynamic_config_lock); mutex_init(&priv->mgmt_lock); rc = sja1105_parse_dt(priv);
The sja1105 hardware seems as concurrent as can be, but when we create a background script that adds/removes a rain of FDB entries without the rtnl_mutex taken, then in parallel we do another operation like run 'bridge fdb show', we can notice these errors popping up: sja1105 spi2.0: port 2 failed to read back entry for 00:01:02:03:00:40 vid 0: -ENOENT sja1105 spi2.0: port 2 failed to add 00:01:02:03:00:40 vid 0 to fdb: -2 sja1105 spi2.0: port 2 failed to read back entry for 00:01:02:03:00:46 vid 0: -ENOENT sja1105 spi2.0: port 2 failed to add 00:01:02:03:00:46 vid 0 to fdb: -2 Luckily what is going on does not require a major rework in the driver. The sja1105_dynamic_config_read() function sends multiple SPI buffers to the peripheral until the operation completes. We should not do anything until the hardware clears the VALID bit. But since there is no locking (i.e. right now we are implicitly serialized by the rtnl_mutex, but if we remove that), it might be possible that the process which performs the dynamic config read is preempted and another one performs a dynamic config write. What will happen in that case is that sja1105_dynamic_config_read(), when it resumes, expects to see VALIDENT set for the entry it reads back. But it won't. This can be corrected by introducing a mutex for serializing SPI accesses to the dynamic config interface which should be atomic with respect to each other. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> --- drivers/net/dsa/sja1105/sja1105.h | 2 ++ drivers/net/dsa/sja1105/sja1105_dynamic_config.c | 12 ++++++++++-- drivers/net/dsa/sja1105/sja1105_main.c | 1 + 3 files changed, 13 insertions(+), 2 deletions(-)