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

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tc_action_net_exit() got an rtnl exclusion in commit
a159d3c4b8 ("net_sched: acquire RTNL in tc_action_net_exit()")

Since then, commit 16af606739 ("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>
This commit is contained in:
Eric Dumazet
2025-07-02 07:12:30 +00:00
committed by Paolo Abeni
parent d23647fd54
commit 84a7d6797e
2 changed files with 8 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
net/sched/act_api.c
View File

@@ -933,18 +933,25 @@ void tcf_idrinfo_destroy(const struct tc_action_ops *ops,
struct tcf_idrinfo *idrinfo)
{
struct idr *idr = &idrinfo->action_idr;
bool mutex_taken = false;
struct tc_action *p;
int ret;
unsigned long id = 1;
unsigned long tmp;
int ret;
idr_for_each_entry_ul(idr, p, tmp, id) {
if (tc_act_in_hw(p) && !mutex_taken) {
rtnl_lock();
mutex_taken = true;
}
ret = __tcf_idr_release(p, false, true);
if (ret == ACT_P_DELETED)
module_put(ops->owner);
else if (ret < 0)
return;
}
if (mutex_taken)
rtnl_unlock();
idr_destroy(&idrinfo->action_idr);
}
EXPORT_SYMBOL(tcf_idrinfo_destroy);