author: Thomas Gleixner <tglx@linutronix.de> 2021-09-18 14:42:35 +0200
committer: David S. Miller <davem@davemloft.net> 2021-09-19 12:48:06 +0100
commit: 2dcb96bacce36021c2f3eaae0cef607b5bb71ede
parent: 48e6d083b3aa006052db687fb26eeceef1d325b6
Commit Summary:
Diffstat:
1 file changed, 23 insertions, 14 deletions
diff --git a/net/core/sock.c b/net/core/sock.c
index 62627e868e03..512e629f9780 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3179,17 +3179,15 @@ EXPORT_SYMBOL(sock_init_data);
void lock_sock_nested(struct sock *sk, int subclass)
{
+ /* The sk_lock has mutex_lock() semantics here. */
+ mutex_acquire(&sk->sk_lock.dep_map, subclass, 0, _RET_IP_);
+
might_sleep();
spin_lock_bh(&sk->sk_lock.slock);
if (sk->sk_lock.owned)
__lock_sock(sk);
sk->sk_lock.owned = 1;
- spin_unlock(&sk->sk_lock.slock);
- /*
- * The sk_lock has mutex_lock() semantics here:
- */
- mutex_acquire(&sk->sk_lock.dep_map, subclass, 0, _RET_IP_);
- local_bh_enable();
+ spin_unlock_bh(&sk->sk_lock.slock);
}
EXPORT_SYMBOL(lock_sock_nested);
@@ -3227,24 +3225,35 @@ EXPORT_SYMBOL(release_sock);
*/
bool lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock)
{
+ /* The sk_lock has mutex_lock() semantics here. */
+ mutex_acquire(&sk->sk_lock.dep_map, 0, 0, _RET_IP_);
+
might_sleep();
spin_lock_bh(&sk->sk_lock.slock);
- if (!sk->sk_lock.owned)
+ if (!sk->sk_lock.owned) {
/*
- * Note : We must disable BH
+ * Fast path return with bottom halves disabled and
+ * sock::sk_lock.slock held.
+ *
+ * The 'mutex' is not contended and holding
+ * sock::sk_lock.slock prevents all other lockers to
+ * proceed so the corresponding unlock_sock_fast() can
+ * avoid the slow path of release_sock() completely and
+ * just release slock.
+ *
+ * From a semantical POV this is equivalent to 'acquiring'
+ * the 'mutex', hence the corresponding lockdep
+ * mutex_release() has to happen in the fast path of
+ * unlock_sock_fast().
*/
return false;
+ }
__lock_sock(sk);
sk->sk_lock.owned = 1;
- spin_unlock(&sk->sk_lock.slock);
- /*
- * The sk_lock has mutex_lock() semantics here:
- */
- mutex_acquire(&sk->sk_lock.dep_map, 0, 0, _RET_IP_);
__acquire(&sk->sk_lock.slock);
- local_bh_enable();
+ spin_unlock_bh(&sk->sk_lock.slock);
return true;
}
EXPORT_SYMBOL(lock_sock_fast);