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net: mscc: ocelot: add locking for the port TX timestamp ID

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The ocelot_port->ts_id is used to:
(a) populate skb->cb[0] for matching the TX timestamp in the PTP IRQ
    with an skb.
(b) populate the REW_OP from the injection header of the ongoing skb.
Only then is ocelot_port->ts_id incremented.

This is a problem because, at least theoretically, another timestampable
skb might use the same ocelot_port->ts_id before that is incremented.
Normally all transmit calls are serialized by the netdev transmit
spinlock, but in this case, ocelot_port_add_txtstamp_skb() is also
called by DSA, which has started declaring the NETIF_F_LLTX feature
since commit 2b86cb8299 ("net: dsa: declare lockless TX feature for
slave ports").  So the logic of using and incrementing the timestamp id
should be atomic per port.

The solution is to use the global ocelot_port->ts_id only while
protected by the associated ocelot_port->ts_id_lock. That's where we
populate skb->cb[0]. Note that for ocelot, ocelot_port_add_txtstamp_skb
is called for the actual skb, but for felix, it is called for the skb's
clone. That is something which will also be changed in the future.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladimir Oltean
2020-09-18 04:07:24 +03:00
committed by David S. Miller
parent 9dda66acdd
commit 6565243c06
4 changed files with 17 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
net/dsa/tag_ocelot.c
View File

@@ -160,11 +160,14 @@ static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
packing(injection, &qos_class, 19, 17, OCELOT_TAG_LEN, PACK, 0);
if (ocelot->ptp && (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
struct sk_buff *clone = DSA_SKB_CB(skb)->clone;
rew_op = ocelot_port->ptp_cmd;
if (ocelot_port->ptp_cmd == IFH_REW_OP_TWO_STEP_PTP) {
rew_op |= (ocelot_port->ts_id % 4) << 3;
ocelot_port->ts_id++;
}
/* Retrieve timestamp ID populated inside skb->cb[0] of the
* clone by ocelot_port_add_txtstamp_skb
*/
if (ocelot_port->ptp_cmd == IFH_REW_OP_TWO_STEP_PTP)
rew_op |= clone->cb[0] << 3;
packing(injection, &rew_op, 125, 117, OCELOT_TAG_LEN, PACK, 0);
}