diff mbox series

[net-next,3/4] net: expedite synchronize_net() for cleanup_net()

Message ID 20250107173838.1130187-4-edumazet@google.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net: reduce RTNL pressure in unregister_netdevice() | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 40 this patch: 40
netdev/build_tools success Errors and warnings before: 0 (+23) this patch: 0 (+23)
netdev/cc_maintainers warning 1 maintainers not CCed: kuniyu@amazon.com
netdev/build_clang success Errors and warnings before: 6710 this patch: 6710
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 4248 this patch: 4248
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 37 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 82 this patch: 82
netdev/source_inline success Was 0 now: 0

Commit Message

Eric Dumazet Jan. 7, 2025, 5:38 p.m. UTC 
cleanup_net() is the single thread responsible
for netns dismantles, and a potential bottleneck.

Before we can get per-netns RTNL, make sure
all synchronize_net() called from this thread
are using rcu_synchronize_expedited().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/net_namespace.h | 2 ++
 net/core/dev.c              | 2 +-
 net/core/net_namespace.c    | 5 +++++
 3 files changed, 8 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 5a2a0df8ad91b677b515b392869c6c755be5c868..a3009bdd7efec0a3b665cbf51c159c323458410a 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -565,4 +565,6 @@  void net_ns_init(void);
 static inline void net_ns_init(void) {}
 #endif
 
+extern struct task_struct *cleanup_net_task;
+
 #endif /* __NET_NET_NAMESPACE_H */
diff --git a/net/core/dev.c b/net/core/dev.c
index ef6426aad84dc00740a1716c8fd4cfd48ee17cf3..342ab7d6001da8983db450f50327fc7915b0a8ba 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11423,7 +11423,7 @@  EXPORT_SYMBOL_GPL(alloc_netdev_dummy);
 void synchronize_net(void)
 {
 	might_sleep();
-	if (rtnl_is_locked())
+	if (current == cleanup_net_task || rtnl_is_locked())
 		synchronize_rcu_expedited();
 	else
 		synchronize_rcu();
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index b5cd3ae4f04cf28d43f8401a3dafebac4a297123..cb39a12b2f8295c605f08b5589932932150a1644 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -588,6 +588,8 @@  static void unhash_nsid(struct net *net, struct net *last)
 
 static LLIST_HEAD(cleanup_list);
 
+struct task_struct *cleanup_net_task;
+
 static void cleanup_net(struct work_struct *work)
 {
 	const struct pernet_operations *ops;
@@ -596,6 +598,8 @@  static void cleanup_net(struct work_struct *work)
 	LIST_HEAD(net_exit_list);
 	LIST_HEAD(dev_kill_list);
 
+	cleanup_net_task = current;
+
 	/* Atomically snapshot the list of namespaces to cleanup */
 	net_kill_list = llist_del_all(&cleanup_list);
 
@@ -670,6 +674,7 @@  static void cleanup_net(struct work_struct *work)
 		put_user_ns(net->user_ns);
 		net_free(net);
 	}
+	cleanup_net_task = NULL;
 }
 
 /**