diff options
| author | Eric Dumazet <edumazet@google.com> | 2026-02-26 05:12:15 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-02-28 04:25:45 +0300 |
| commit | 5151ec54f5861ad71e08190a7ce2173df788d36a (patch) | |
| tree | ae557b45be6df4c14be5923766e21b958b373de3 /include | |
| parent | b99ccb37eda85a9070d1f9f275fc8ca1f4e33024 (diff) | |
| download | linux-5151ec54f5861ad71e08190a7ce2173df788d36a.tar.xz | |
net: use try_cmpxchg() in lock_sock_nested()
Add a fast path in lock_sock_nested(), to avoid acquiring
the socket spinlock only to set @owned to one:
spin_lock_bh(&sk->sk_lock.slock);
if (unlikely(sock_owned_by_user_nocheck(sk)))
__lock_sock(sk);
sk->sk_lock.owned = 1;
spin_unlock_bh(&sk->sk_lock.slock);
On x86_64 compiler generates something quite efficient:
00000000000077c0 <lock_sock_nested>:
77c0: f3 0f 1e fa endbr64
77c4: e8 00 00 00 00 call __fentry__
77c9: b9 01 00 00 00 mov $0x1,%ecx
77ce: 31 c0 xor %eax,%eax
77d0: f0 48 0f b1 8f 48 01 00 00 lock cmpxchg %rcx,0x148(%rdi)
77d9: 75 06 jne slow_path
77db: 2e e9 00 00 00 00 cs jmp __x86_return_thunk-0x4
slow_path: ...
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://patch.msgid.link/20260226021215.1764237-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/sock.h | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/include/net/sock.h b/include/net/sock.h index e7099d3d0416..a7a8b31e9877 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -81,8 +81,13 @@ * mini-semaphore synchronizes multiple users amongst themselves. */ typedef struct { - spinlock_t slock; - int owned; + union { + struct slock_owned { + int owned; + spinlock_t slock; + }; + long combined; + }; wait_queue_head_t wq; /* * We express the mutex-alike socket_lock semantics |