From patchwork Fri Oct 10 05:24:51 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 398451 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id F37421400E2 for ; Fri, 10 Oct 2014 16:25:30 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751739AbaJJFZ0 (ORCPT ); Fri, 10 Oct 2014 01:25:26 -0400 Received: from mail-pa0-f73.google.com ([209.85.220.73]:53201 "EHLO mail-pa0-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751644AbaJJFZE (ORCPT ); Fri, 10 Oct 2014 01:25:04 -0400 Received: by mail-pa0-f73.google.com with SMTP id et14so234692pad.4 for ; Thu, 09 Oct 2014 22:25:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=OkID9L7SS1+GOkQxJienXAtcAHwCRw5pwKonwhafxKA=; b=HNNHIk+UHl25sYAYLts/sSgI5l0xI2K+5X390J2zbEfajCd1leTEPwzjI9ZOpt5cnH CiM/TEABoV8Pvyvq47T0CieDhsnHLmWeQwfVP65//y/EmQWLKkv3SUHp5HQ5wEjO0qUz QXIcgk4ENW0xHCaDfdS9Gxkow4rLdqcSgT+rdnEQbnj8YAzolrxNn0qQ2yXob6vChPn9 SWZZiDdsj9P8fwmkhqpAaSgBX3uxttgKWTf2dgeCuOiaLIhM7izmd46FuBUYnLKMVu1Q 16liPPy4T7dIDhiibvVwIanyrNUt310bUE6d0D5R6it7lW67eO62NpZ2fleoK7sRnovy Hbxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=OkID9L7SS1+GOkQxJienXAtcAHwCRw5pwKonwhafxKA=; b=baq4D44xhjg78NJYCB+AdkuaPPH5hK4MQQ7t7L7zJLhtklkZz4KIs/Q5n/dqkQB+DU w0/nEybcMjapHTOnWg7KH/BTJqNHaiHVIB6oy7Fp3PQP9xvyeADZjHbtfiuFVRKRrtBx I0m39IweKXz3YA/atWecH4LwBmDps/jQ2TkqiWl6I1ZKQBeQbkb0BfSejHEhYnhvasuf WZp6hMw87FSjmLE+w86ZigyAnwsphPD0YvRyV1qlY3EkjtEjcBY8J8AusZ0J1LWlDQeX bjXskriGo28uFbE2UTTwrgOmTl8NJ0//7mhBSKlwb30vlvy5al5IgHKo6RtgTgp32Mb7 EopQ== X-Gm-Message-State: ALoCoQkJTHzhmeekq3O2zzqlUj3vKoSBCDo1BPfnUsN0CJAA/fduOuw+ku/ydA1nvcSitDtYBp2Y X-Received: by 10.70.36.34 with SMTP id n2mr1826201pdj.5.1412918704402; Thu, 09 Oct 2014 22:25:04 -0700 (PDT) Received: from corpmail-nozzle1-1.hot.corp.google.com ([100.108.1.104]) by gmr-mx.google.com with ESMTPS id n24si276296yha.6.2014.10.09.22.25.03 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 09 Oct 2014 22:25:04 -0700 (PDT) Received: from manihi.mtv.corp.google.com ([172.17.131.143]) by corpmail-nozzle1-1.hot.corp.google.com with ESMTP id RY2QmoDb.1; Thu, 09 Oct 2014 22:25:04 -0700 Received: by manihi.mtv.corp.google.com (Postfix, from userid 160623) id 72CA4A0A01; Thu, 9 Oct 2014 22:25:03 -0700 (PDT) From: Eric Dumazet To: "David S. Miller" Cc: netdev@vger.kernel.org, Alexander Duyck , Andres Lagar-Cavilla , Greg Thelen , Hugh Dickins , David Rientjes , Eric Dumazet Subject: [PATCH net 2/5] igb: fix race accessing page->_count Date: Thu, 9 Oct 2014 22:24:51 -0700 Message-Id: <1412918694-22882-3-git-send-email-edumazet@google.com> X-Mailer: git-send-email 2.1.0.rc2.206.gedb03e5 In-Reply-To: <1412918694-22882-1-git-send-email-edumazet@google.com> References: <1412918694-22882-1-git-send-email-edumazet@google.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This is illegal to use atomic_set(&page->_count, 2) even if we 'own' the page. Other entities in the kernel need to use get_page_unless_zero() to get a reference to the page before testing page properties, so we could loose a refcount increment. Signed-off-by: Eric Dumazet Acked-by: Jeff Kirsher --- drivers/net/ethernet/intel/igb/igb_main.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index ae59c0b108c5..a21b14495ebd 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -6545,11 +6545,10 @@ static bool igb_can_reuse_rx_page(struct igb_rx_buffer *rx_buffer, /* flip page offset to other buffer */ rx_buffer->page_offset ^= IGB_RX_BUFSZ; - /* since we are the only owner of the page and we need to - * increment it, just set the value to 2 in order to avoid - * an unnecessary locked operation + /* Even if we own the page, we are not allowed to use atomic_set() + * This would break get_page_unless_zero() users. */ - atomic_set(&page->_count, 2); + atomic_inc(&page->_count); #else /* move offset up to the next cache line */ rx_buffer->page_offset += truesize;