From patchwork Wed Jan 8 21:35:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Fastabend X-Patchwork-Id: 1219988 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: incoming-bpf@patchwork.ozlabs.org Delivered-To: patchwork-incoming-bpf@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=bpf-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="bes7gIYs"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 47tMwm39CDz9sPK for ; Thu, 9 Jan 2020 08:35:20 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726497AbgAHVfU (ORCPT ); Wed, 8 Jan 2020 16:35:20 -0500 Received: from mail-il1-f195.google.com ([209.85.166.195]:45465 "EHLO mail-il1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726179AbgAHVfT (ORCPT ); Wed, 8 Jan 2020 16:35:19 -0500 Received: by mail-il1-f195.google.com with SMTP id p8so3893806iln.12; Wed, 08 Jan 2020 13:35:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:date:message-id:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=pGjnNwKmSOomeeUgLDOsf11LLdbS6lxP9M2BwdBU5ao=; b=bes7gIYsXruKZ2rdAWH0qwjhRAyDrcGA6mL1lHQ8MfALaHY4neWpXMi6nrbsBzgyiH O6imQ/iaIUgXpBB1/bfoDWqahFmXwxa8LQWTwexVG4AmM3+PDpkRdoen3pWZQBzkYNXo AeXelXr6amubUMTvG8GtIj41rh2tYh/cuyWhxiCvK8WmG9rvfrL/dsbflibc1tgGEpzc wMMDJNXXuAnt4gDE+AHgABPS2ZVoKhQoB9I5Z4w9cJLBVhKCRTF/5zir2kslOi4SOPvy Q+1HOA0Nbmjdhue9yeEXbDyZnBUutfZyza3fx0ZG5bnFUsII+3YfqohpAX7wS+b6fZR7 gsGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:date:message-id:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=pGjnNwKmSOomeeUgLDOsf11LLdbS6lxP9M2BwdBU5ao=; b=hS9N1lxD7oiwg/QX+Yp01E8gXiCc0K0Jz6fiG9HThc7AAJ8EVQM5quzZDVPGdUIwxn +zNvy3qcQxEO2/8tn6AWhSrLmgGGmlNqgB4EWs22hq0qh8TEjcE6+3FjEUQpF+5Y+ivb 6Uzw+VtCksAZ++QCfJl/cyRr5BKHiRhwACfCiWsuyXtqT/PasSOBIoGp878NpZ94TExb WKONMqU422VKDDgbB3ZnWfa+Qlr4xhtSiVdiGpX2JnLzZ8Ma4KVRDPaupsB/H+p0mjIL NM6VuEjsPhQbExHIpYfk4obD+SM8+VBegT0JFK2w1DJKN8lkoKterQKSFhOIfiZC5bRC dcPQ== X-Gm-Message-State: APjAAAUfASq+l9qRLNl7MZ8c60vYI7Xw0EOvrgSyenzrdZki2+uRYIK5 +Ru2I7ULb65G7PlKmuwFJmw= X-Google-Smtp-Source: APXvYqy5RdtK3f/7PixAgAsO2qdBz451nUje8NDx9ycz7aWmMXM+cKbotfQUAJg/r7DWNOABOjq1xg== X-Received: by 2002:a92:cb11:: with SMTP id s17mr6059966ilo.114.1578519319116; Wed, 08 Jan 2020 13:35:19 -0800 (PST) Received: from [127.0.1.1] ([184.63.162.180]) by smtp.gmail.com with ESMTPSA id l83sm1330187ild.34.2020.01.08.13.35.12 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 Jan 2020 13:35:18 -0800 (PST) Subject: [bpf PATCH 2/2] bpf: xdp, remove no longer required rcu_read_{un}lock() From: John Fastabend To: bjorn.topel@gmail.com, bpf@vger.kernel.org, toke@redhat.com Cc: netdev@vger.kernel.org, john.fastabend@gmail.com, ast@kernel.org, daniel@iogearbox.net Date: Wed, 08 Jan 2020 13:35:06 -0800 Message-ID: <157851930654.21459.7236323146782270917.stgit@john-Precision-5820-Tower> In-Reply-To: <157851907534.21459.1166135254069483675.stgit@john-Precision-5820-Tower> References: <157851907534.21459.1166135254069483675.stgit@john-Precision-5820-Tower> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Now that we depend on rcu_call() and synchronize_rcu() to also wait for preempt_disabled region to complete the rcu read critical section in __dev_map_flush() is no longer relevant. These originally ensured the map reference was safe while a map was also being free'd. But flush by new rules can only be called from preempt-disabled NAPI context. The synchronize_rcu from the map free path and the rcu_call from the delete path will ensure the reference here is safe. So lets remove the rcu_read_lock and rcu_read_unlock pair to avoid any confusion around how this is being protected. If the rcu_read_lock was required it would mean errors in the above logic and the original patch would also be wrong. Fixes: 0536b85239b84 ("xdp: Simplify devmap cleanup") Signed-off-by: John Fastabend Acked-by: Song Liu --- kernel/bpf/devmap.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index f0bf525..0129d4a 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -378,10 +378,8 @@ void __dev_map_flush(void) struct list_head *flush_list = this_cpu_ptr(&dev_map_flush_list); struct xdp_bulk_queue *bq, *tmp; - rcu_read_lock(); list_for_each_entry_safe(bq, tmp, flush_list, flush_node) bq_xmit_all(bq, XDP_XMIT_FLUSH); - rcu_read_unlock(); } /* rcu_read_lock (from syscall and BPF contexts) ensures that if a delete and/or