From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f201.google.com (mail-qk1-f201.google.com [209.85.222.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B77AC11CBA for ; Wed, 25 Feb 2026 03:32:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771990340; cv=none; b=MvIKiRMeI4y2NbMP04xmFYLAavcs00H/IL1Q1VAxSv59ix16QsiNe9AnzhCvK6uu964D+ps2flkBxf7sbxBN2MNoBNRAQW8grLQ8TayNb2otwBJKwmgExi6ymtRsTZT2ZofPI2WH3Y+s1gpc596c/8c1poVIoJ55k3bkDl9dG2k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771990340; c=relaxed/simple; bh=JeWWhjlGQSAE8+JVghoKUWiFAPmhlTzy71NR5YC4I2k=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=feAccz6a+7A95ESCkxult9y857EEalYSEayK0SyHtRHqlJ9yTeHY5s3kW1G/zhqzYqeP+U+2qcFShNWiSqToUXESxV/JDRrDn9YrnxgvEIhl77nOrE/kyIbteEPgq4QkvzzrrBRtTZYWfM5Z+U42L3yhuCFCPlazeQBDHfL2ptM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=JJfzk7D/; arc=none smtp.client-ip=209.85.222.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="JJfzk7D/" Received: by mail-qk1-f201.google.com with SMTP id af79cd13be357-8cb4817f3c8so4646180885a.3 for ; Tue, 24 Feb 2026 19:32:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1771990339; x=1772595139; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=PBH2ht8SvVICfDQUa0pPrXGp/+5LQJ28p1mb+pPA6q8=; b=JJfzk7D/Z68TaRWgJxUTFrZ71CCwU/fkr01kzCj4Z9vqOkadODRADxALIaUKAKCGBi WzgwcvAjcoJDsjlkQ1YCCw7TcWdzyhBscjVT0w4/NGGomPXxkWxMjNjCgOsgfGVA6m2l wiI+bzxaS1kTTC+0mowMHELx4acx4wCY4oob+tYyRmTNoQ/+fnM6DaZeLg38nMY6O+lo 7ZMU69rc1ZDijX2Gawcfa93edmw/Rd6nU8wU41e/LvzE/K8ejODZJ8V+HhZmYwclTaab 9dXLZ4iBcWrQ3CFVl5t+F0AoGMSQg6aNZ9NDBmRMtHFiFKfH0HNS3LjqYG/Y9IqRMHQV yYdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771990339; x=1772595139; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=PBH2ht8SvVICfDQUa0pPrXGp/+5LQJ28p1mb+pPA6q8=; b=gKvLj1GqkIpCB9/5I+PRmzJsBto+Ve7kNvAl12rYljFQY4ASjkSfq4OshLOIEeKJdz KfrfK6IhfG3gYv43rSKGsBl3vfUPOMfneG6JzPpwn+EzOTupPMY2+D1b43ouXeVf4CWB xpTnuAYLytDZ/kr1Btpbs6nKQ6W4p7WxCaxZlCFXz6//UQBk7nHejgEEJYqDwGnoh8Hj VfWpKbArf382wR/yytjHbaaQ1McQ0hMwCxxAoNfBGUs1v2Mko9qr0qTzYLTvb1AMBfpp h8WO31+Z/sI5pzY5EjSCIsQZeuhIPXfpvPDl4YUi0aK1LGT1+V7d+JwkJT4XXHy9Ykgs +6BA== X-Forwarded-Encrypted: i=1; AJvYcCVHnYrCodQUt656b5TaNhXsNvVsT54Zk0ZGJTEPwYAhPtI7uBLuvMsqhcyrxkMYojoPuC3FfCg=@vger.kernel.org X-Gm-Message-State: AOJu0YxZL4wkguqPDHtTTbdN4aOYwxf5WdsovXIK8X+OERVse8aXdIs1 s6Xt1MPMuAAJ0eKD0HeUyd6Qg1hgElpJ01AHEV3ed0SjE2qA6qkQ7xBGzh24cGzUC3mYrjbHh0E tEIMtBWHQxl6tfA== X-Received: from qknwm15.prod.google.com ([2002:a05:620a:580f:b0:8c5:2ecb:a10a]) (user=edumazet job=prod-delivery.src-stubby-dispatcher) by 2002:a05:620a:1a85:b0:8c6:a5bb:f464 with SMTP id af79cd13be357-8cb8ca80011mr1772979885a.66.1771990338561; Tue, 24 Feb 2026 19:32:18 -0800 (PST) Date: Wed, 25 Feb 2026 03:32:16 +0000 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.53.0.414.gf7e9f6c205-goog Message-ID: <20260225033216.601205-1-edumazet@google.com> Subject: [PATCH net-next] net: use cmpxchg() in lock_sock_nested() From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Kuniyuki Iwashima , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet Content-Type: text/plain; charset="UTF-8" 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: ffffffff81e96100 : ffffffff81e96100: f3 0f 1e fa endbr64 ffffffff81e96104: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) ffffffff81e96109: b9 01 00 00 00 mov $0x1,%ecx ffffffff81e9610e: 31 c0 xor %eax,%eax ffffffff81e96110: f0 48 0f b1 8f 48 01 lock cmpxchg %rcx,0x148(%rdi) ffffffff81e96117: 00 00 ffffffff81e96119: 48 85 c0 test %rax,%rax ffffffff81e9611c: 74 33 je ffffffff81e96151 ...// slow path ffffffff81e96151: 2e e9 19 c4 33 00 cs jmp ffffffff821d2570 <__pi___x86_return_thunk> Signed-off-by: Eric Dumazet --- include/net/sock.h | 9 +++++++-- net/core/sock.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index 55b61e4b0d8318887d527e919fc1103d78ac6d14..84c21fb38a28406e387dc33e0fb5decd18893950 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 diff --git a/net/core/sock.c b/net/core/sock.c index cfb2a6209946089669882cdbd5d1b36c53838989..2a03d1432111f2dcea9d700f80efb7b0bb4a47d8 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -3780,6 +3780,16 @@ void noinline lock_sock_nested(struct sock *sk, int subclass) mutex_acquire(&sk->sk_lock.dep_map, subclass, 0, _RET_IP_); might_sleep(); +#ifdef CONFIG_64BIT + if (sizeof(struct slock_owned) == sizeof(long)) { + socket_lock_t tmp; + + tmp.slock = __SPIN_LOCK_UNLOCKED(tmp.slock); + tmp.owned = 1; + if (likely(!cmpxchg(&sk->sk_lock.combined, 0, tmp.combined))) + return; + } +#endif spin_lock_bh(&sk->sk_lock.slock); if (unlikely(sock_owned_by_user_nocheck(sk))) __lock_sock(sk); -- 2.53.0.414.gf7e9f6c205-goog