net/sched: acp_api: no longer acquire RTNL in tc_action_net_exit()

tc_action_net_exit() got an rtnl exclusion in commit
a159d3c4 ("net_sched: acquire RTNL in tc_action_net_exit()")

Since then, commit 16af6067 ("net: sched: implement reference
counted action release") made this RTNL exclusion obsolete for
most cases.

Only tcf_action_offload_del() might still require it.

Move the rtnl locking into tcf_idrinfo_destroy() when
an offload action is found.

Most netns do not have actions, yet deleting them is adding a lot
of pressure on RTNL, which is for many the most contended mutex
in the kernel.

We are moving to a per-netns 'rtnl', so tc_action_net_exit()
will not be able to grab 'rtnl' a single time for a batch of netns.

Before the patch:

perf probe -a rtnl_lock

perf record -e probe:rtnl_lock -a /bin/bash -c 'unshare -n "/bin/true"; sleep 1'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.305 MB perf.data (25 samples) ]

After the patch:

perf record -e probe:rtnl_lock -a /bin/bash -c 'unshare -n "/bin/true"; sleep 1'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.304 MB perf.data (9 samples) ]

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vlad Buslov <vladbu@nvidia.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://patch.msgid.link/20250702071230.1892674-1-edumazet@google.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>