Merge branch 'net_sched-adapt-qdiscs-for-reentrant-enqueue-cases'

Victor Nogueira says:

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net_sched: Adapt qdiscs for reentrant enqueue cases

As described in Gerrard's report [1], there are cases where netem can
make the qdisc enqueue callback reentrant. Some qdiscs (drr, hfsc, ets,
qfq) break whenever the enqueue callback has reentrant behaviour.
This series addresses these issues by adding extra checks that cater for
these reentrant corner cases. This series has passed all relevant test
cases in the TDC suite.

[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
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Link: https://patch.msgid.link/20250425220710.3964791-1-victor@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>