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net: renesas: rswitch: rework ts tags management

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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: 33f5d733b5 ("net: renesas: rswitch: Improve TX timestamp accuracy")
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Link: https://patch.msgid.link/20241212062558.436455-1-nikita.yoush@cogentembedded.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Nikita Yushchenko 2024-12-12 11:25:58 +05:00 committed by Jakub Kicinski
parent cb85f2b897
commit 922b4b955a
2 changed files with 39 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
drivers/net/ethernet/renesas/rswitch.c
View File

@ -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;
}
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_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);
}

13
drivers/net/ethernet/renesas/rswitch.h
View File

@ -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;