net: renesas: rswitch: rework ts tags management

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[ Upstream commit 922b4b955a ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Nikita Yushchenko 2024-12-12 11:25:58 +05:00 • committed by Greg Kroah-Hartman

parent 6cd7cad950

commit ce2fade187

2 changed files with 42 additions and 45 deletions

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68

drivers/net/ethernet/renesas/rswitch.c

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13

drivers/net/ethernet/renesas/rswitch.h

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