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102 lines
3.5 KiB
Diff
102 lines
3.5 KiB
Diff
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From 06efc9b8a1360cad83cae6e71558e5458cc1fbf3 Mon Sep 17 00:00:00 2001
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From: Vladimir Oltean <vladimir.oltean@nxp.com>
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Date: Tue, 29 Nov 2022 16:12:14 +0200
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Subject: [PATCH 07/14] net: dpaa2-eth: assign priv->mac after
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dpaa2_mac_connect() call
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There are 2 requirements for correct code:
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- Any time the driver accesses the priv->mac pointer at runtime, it
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either holds NULL to indicate a DPNI-DPNI connection (or unconnected
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DPNI), or a struct dpaa2_mac whose phylink instance was fully
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initialized (created and connected to the PHY). No changes are made to
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priv->mac while it is being used. Currently, rtnl_lock() watches over
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the call to dpaa2_eth_connect_mac(), so it serves the purpose of
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serializing this with all readers of priv->mac.
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- dpaa2_mac_connect() should run unlocked, because inside it are 2
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phylink calls with incompatible locking requirements: phylink_create()
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requires that the rtnl_mutex isn't held, and phylink_fwnode_phy_connect()
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requires that the rtnl_mutex is held. The only way to solve those
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contradictory requirements is to let dpaa2_mac_connect() take
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rtnl_lock() when it needs to.
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To solve both requirements, we need to identify the writer side of the
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priv->mac pointer, which can be wrapped in a mutex private to the driver
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in a future patch. The dpaa2_mac_connect() cannot be part of the writer
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side critical section, because of an AB/BA deadlock with rtnl_lock().
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So the strategy needs to be that where we prepare the DPMAC by calling
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dpaa2_mac_connect(), and only make priv->mac point to it once it's fully
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prepared. This ensures that the writer side critical section has the
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absolute minimum surface it can.
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The reverse strategy is adopted in the dpaa2_eth_disconnect_mac() code
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path. This makes sure that priv->mac is NULL when we start tearing down
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the DPMAC that we disconnected from, and concurrent code will simply not
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see it.
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No locking changes in this patch (concurrent code is still blocked by
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the rtnl_mutex).
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Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
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Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
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Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
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Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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---
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.../net/ethernet/freescale/dpaa2/dpaa2-eth.c | 21 +++++++++++--------
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1 file changed, 12 insertions(+), 9 deletions(-)
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--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
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+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
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@@ -4443,9 +4443,8 @@ static int dpaa2_eth_connect_mac(struct
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err = dpaa2_mac_open(mac);
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if (err)
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goto err_free_mac;
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- priv->mac = mac;
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- if (dpaa2_eth_is_type_phy(priv)) {
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+ if (dpaa2_mac_is_type_phy(mac)) {
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err = dpaa2_mac_connect(mac);
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if (err && err != -EPROBE_DEFER)
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netdev_err(priv->net_dev, "Error connecting to the MAC endpoint: %pe",
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@@ -4454,11 +4453,12 @@ static int dpaa2_eth_connect_mac(struct
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goto err_close_mac;
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}
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+ priv->mac = mac;
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+
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return 0;
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err_close_mac:
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dpaa2_mac_close(mac);
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- priv->mac = NULL;
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err_free_mac:
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kfree(mac);
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return err;
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@@ -4466,15 +4466,18 @@ err_free_mac:
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static void dpaa2_eth_disconnect_mac(struct dpaa2_eth_priv *priv)
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{
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- if (dpaa2_eth_is_type_phy(priv))
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- dpaa2_mac_disconnect(priv->mac);
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+ struct dpaa2_mac *mac = priv->mac;
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+
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+ priv->mac = NULL;
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- if (!dpaa2_eth_has_mac(priv))
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+ if (!mac)
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return;
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- dpaa2_mac_close(priv->mac);
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- kfree(priv->mac);
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- priv->mac = NULL;
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+ if (dpaa2_mac_is_type_phy(mac))
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+ dpaa2_mac_disconnect(mac);
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+
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+ dpaa2_mac_close(mac);
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+ kfree(mac);
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}
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static irqreturn_t dpni_irq0_handler_thread(int irq_num, void *arg)
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