Commit 922b4b95 authored by Nikita Yushchenko's avatar Nikita Yushchenko Committed by Jakub Kicinski
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net: renesas: rswitch: rework ts tags management 



The existing linked list based implementation of how ts tags are
assigned and managed is unsafe against concurrency and corner cases:
- element addition in tx processing can race against element removal
  in ts queue completion,
- element removal in ts queue completion can race against element
  removal in device close,
- if a large number of frames gets added to tx queue without ts queue
  completions in between, elements with duplicate tag values can get
  added.

Use a different implementation, based on per-port used tags bitmaps and
saved skb arrays.

Safety for addition in tx processing vs removal in ts completion is
provided by:

    tag = find_first_zero_bit(...);
    smp_mb();
    <write rdev->ts_skb[tag]>
    set_bit(...);

  vs

    <read rdev->ts_skb[tag]>
    smp_mb();
    clear_bit(...);

Safety for removal in ts completion vs removal in device close is
provided by using atomic read-and-clear for rdev->ts_skb[tag]:

    ts_skb = xchg(&rdev->ts_skb[tag], NULL);
    if (ts_skb)
        <handle it>

Fixes: 33f5d733 ("net: renesas: rswitch: Improve TX timestamp accuracy")
Signed-off-by: default avatarNikita Yushchenko <nikita.yoush@cogentembedded.com>
Link: https://patch.msgid.link/20241212062558.436455-1-nikita.yoush@cogentembedded.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent cb85f2b8

drivers/net/ethernet/renesas/rswitch.c

+39 −35
Original line number Diff line number Diff line
@@ -547,7 +547,6 @@ static int rswitch_gwca_ts_queue_alloc(struct rswitch_private *priv) 
	desc = &gq->ts_ring[gq->ring_size];

	desc->desc.die_dt = DT_LINKFIX;

	rswitch_desc_set_dptr(&desc->desc, gq->ring_dma);

	INIT_LIST_HEAD(&priv->gwca.ts_info_list);



	return 0;

}
@@ -1003,9 +1002,10 @@ static int rswitch_gwca_request_irqs(struct rswitch_private *priv) 
static void rswitch_ts(struct rswitch_private *priv)

{

	struct rswitch_gwca_queue *gq = &priv->gwca.ts_queue;

	struct rswitch_gwca_ts_info *ts_info, *ts_info2;

	struct skb_shared_hwtstamps shhwtstamps;

	struct rswitch_ts_desc *desc;

	struct rswitch_device *rdev;

	struct sk_buff *ts_skb;

	struct timespec64 ts;

	unsigned int num;

	u32 tag, port;
@@ -1015,23 +1015,28 @@ static void rswitch_ts(struct rswitch_private *priv) 
		dma_rmb();



		port = TS_DESC_DPN(__le32_to_cpu(desc->desc.dptrl));

		if (unlikely(port >= RSWITCH_NUM_PORTS))

			goto next;

		rdev = priv->rdev[port];



		tag = TS_DESC_TSUN(__le32_to_cpu(desc->desc.dptrl));

		if (unlikely(tag >= TS_TAGS_PER_PORT))

			goto next;

		ts_skb = xchg(&rdev->ts_skb[tag], NULL);

		smp_mb(); /* order rdev->ts_skb[] read before bitmap update */

		clear_bit(tag, rdev->ts_skb_used);



		list_for_each_entry_safe(ts_info, ts_info2, &priv->gwca.ts_info_list, list) {

			if (!(ts_info->port == port && ts_info->tag == tag))

				continue;

		if (unlikely(!ts_skb))

			goto next;



		memset(&shhwtstamps, 0, sizeof(shhwtstamps));

		ts.tv_sec = __le32_to_cpu(desc->ts_sec);

		ts.tv_nsec = __le32_to_cpu(desc->ts_nsec & cpu_to_le32(0x3fffffff));

		shhwtstamps.hwtstamp = timespec64_to_ktime(ts);

			skb_tstamp_tx(ts_info->skb, &shhwtstamps);

			dev_consume_skb_irq(ts_info->skb);

			list_del(&ts_info->list);

			kfree(ts_info);

			break;

		}

		skb_tstamp_tx(ts_skb, &shhwtstamps);

		dev_consume_skb_irq(ts_skb);



next:

		gq->cur = rswitch_next_queue_index(gq, true, 1);

		desc = &gq->ts_ring[gq->cur];

	}
@@ -1576,8 +1581,9 @@ static int rswitch_open(struct net_device *ndev) 
static int rswitch_stop(struct net_device *ndev)

{

	struct rswitch_device *rdev = netdev_priv(ndev);

	struct rswitch_gwca_ts_info *ts_info, *ts_info2;

	struct sk_buff *ts_skb;

	unsigned long flags;

	unsigned int tag;



	netif_tx_stop_all_queues(ndev);
@@ -1594,12 +1600,13 @@ static int rswitch_stop(struct net_device *ndev) 
	if (bitmap_empty(rdev->priv->opened_ports, RSWITCH_NUM_PORTS))

		iowrite32(GWCA_TS_IRQ_BIT, rdev->priv->addr + GWTSDID);



	list_for_each_entry_safe(ts_info, ts_info2, &rdev->priv->gwca.ts_info_list, list) {

		if (ts_info->port != rdev->port)

			continue;

		dev_kfree_skb_irq(ts_info->skb);

		list_del(&ts_info->list);

		kfree(ts_info);

	for (tag = find_first_bit(rdev->ts_skb_used, TS_TAGS_PER_PORT);

	     tag < TS_TAGS_PER_PORT;

	     tag = find_next_bit(rdev->ts_skb_used, TS_TAGS_PER_PORT, tag + 1)) {

		ts_skb = xchg(&rdev->ts_skb[tag], NULL);

		clear_bit(tag, rdev->ts_skb_used);

		if (ts_skb)

			dev_kfree_skb(ts_skb);

	}



	return 0;
@@ -1612,20 +1619,17 @@ static bool rswitch_ext_desc_set_info1(struct rswitch_device *rdev, 
	desc->info1 = cpu_to_le64(INFO1_DV(BIT(rdev->etha->index)) |

				  INFO1_IPV(GWCA_IPV_NUM) | INFO1_FMT);

	if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {

		struct rswitch_gwca_ts_info *ts_info;

		unsigned int tag;



		ts_info = kzalloc(sizeof(*ts_info), GFP_ATOMIC);

		if (!ts_info)

		tag = find_first_zero_bit(rdev->ts_skb_used, TS_TAGS_PER_PORT);

		if (tag == TS_TAGS_PER_PORT)

			return false;

		smp_mb(); /* order bitmap read before rdev->ts_skb[] write */

		rdev->ts_skb[tag] = skb_get(skb);

		set_bit(tag, rdev->ts_skb_used);



		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;

		rdev->ts_tag++;

		desc->info1 |= cpu_to_le64(INFO1_TSUN(rdev->ts_tag) | INFO1_TXC);



		ts_info->skb = skb_get(skb);

		ts_info->port = rdev->port;

		ts_info->tag = rdev->ts_tag;

		list_add_tail(&ts_info->list, &rdev->priv->gwca.ts_info_list);

		desc->info1 |= cpu_to_le64(INFO1_TSUN(tag) | INFO1_TXC);



		skb_tx_timestamp(skb);

	}

drivers/net/ethernet/renesas/rswitch.h

+3 −10
Original line number Diff line number Diff line
@@ -972,14 +972,6 @@ struct rswitch_gwca_queue { 
	};

};



struct rswitch_gwca_ts_info {

	struct sk_buff *skb;

	struct list_head list;



	int port;

	u8 tag;

};



#define RSWITCH_NUM_IRQ_REGS	(RSWITCH_MAX_NUM_QUEUES / BITS_PER_TYPE(u32))

struct rswitch_gwca {

	unsigned int index;
@@ -989,7 +981,6 @@ struct rswitch_gwca { 
	struct rswitch_gwca_queue *queues;

	int num_queues;

	struct rswitch_gwca_queue ts_queue;

	struct list_head ts_info_list;

	DECLARE_BITMAP(used, RSWITCH_MAX_NUM_QUEUES);

	u32 tx_irq_bits[RSWITCH_NUM_IRQ_REGS];

	u32 rx_irq_bits[RSWITCH_NUM_IRQ_REGS];
@@ -997,6 +988,7 @@ struct rswitch_gwca { 
};



#define NUM_QUEUES_PER_NDEV	2

#define TS_TAGS_PER_PORT	256

struct rswitch_device {

	struct rswitch_private *priv;

	struct net_device *ndev;
@@ -1004,7 +996,8 @@ struct rswitch_device { 
	void __iomem *addr;

	struct rswitch_gwca_queue *tx_queue;

	struct rswitch_gwca_queue *rx_queue;

	u8 ts_tag;

	struct sk_buff *ts_skb[TS_TAGS_PER_PORT];

	DECLARE_BITMAP(ts_skb_used, TS_TAGS_PER_PORT);

	bool disabled;



	int port;