From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f68.google.com (mail-pa0-f68.google.com [209.85.220.68]) by dpdk.org (Postfix) with ESMTP id 8DFC137AA for ; Fri, 2 Sep 2016 07:25:14 +0200 (CEST) Received: by mail-pa0-f68.google.com with SMTP id hm5so582151pac.1 for ; Thu, 01 Sep 2016 22:25:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Kq0BRQxbXKNMOdtflvqjLlCPMddeiNrXI2izzVd3MvY=; b=S36Hr76IXzz8VWShJEK9j5bTV1hOOMdD17jgWXT2zvRuccpEvdTvPulNF0QYMyhrIx uvDZsSPB/vFVuqFtio5wd8Qo3iRrl15qJHYUnzGxqQMSRJ4K5x6NlZAH8OFVqOPHlec4 /6/90wFrGNiSj9x9Bwco/4Fdi0fvfZvn2lbw8gP6wYpMYizznuLAaUZxtI222Rjo48jr o3xJZ5qjVdoqoEwapsM8x5IJWZorcI3+qkwcl3SnGz2zu4nDD1DQEqHVcNwu0VgPLrgp uBvtjP8SbEfdVyQATmqjhTtCvKZkmkaShSz/cFfBpOwKuNeQb5UdbGM/HsAeoHWs9xt5 rfVA== 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:mime-version :content-transfer-encoding; bh=Kq0BRQxbXKNMOdtflvqjLlCPMddeiNrXI2izzVd3MvY=; b=MUtF6m2x9o3tRtXPy1SbKbWhcQcunvd2J/00+OwExlpwJhCptCWzc23IZi0L0b7BPa H6H95/yzauVUVMW2LO/kf3YJVHOi01tK/902FBOIRphpZr2x0+HnhV8UdtGocS9sqawX RjRc4nrFDwk4M+IgU9ICVc/pPhGKkcLlJA7V2W4t4dJwM3h+9x2p02s9Ft9fBY4+OaiL 0ahk4SZOzqryxNRS3CXNjxk0H4fPndH5Dz/DWJLjYhAxaUFO1V9YGof1EaXsuapTOmLu JQvWILJW3lR3LG0xQw6Xp91Lijd81WdA+XIku9gA1dxtdEJ86wbyzggiW49WC3wSVsfW 6JIg== X-Gm-Message-State: AE9vXwO0BYC18oUAZgYa8/8lc/PhFWf2iyQgi+fBh58BwTbwkpzDzAZr/TIJPZI6/DSA1w== X-Received: by 10.66.242.201 with SMTP id ws9mr33035674pac.7.1472793913530; Thu, 01 Sep 2016 22:25:13 -0700 (PDT) Received: from localhost.localdomain (2607-8700-0101-a4c2-ca35-dc2d-6794-aee9.16clouds.com. [2607:8700:101:a4c2:ca35:dc2d:6794:aee9]) by smtp.googlemail.com with ESMTPSA id o80sm11300825pfa.67.2016.09.01.22.25.12 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Sep 2016 22:25:13 -0700 (PDT) From: lilinzhe To: dev@dpdk.org Cc: =?UTF-8?q?=E6=9D=8E=E6=9E=97=E5=93=B2?= Date: Fri, 2 Sep 2016 13:25:06 +0800 Message-Id: <1472793906-5699-1-git-send-email-slayercat.subscription@gmail.com> X-Mailer: git-send-email 2.7.0.rc2 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [dpdk-dev] [PATCH] mbuf: fix atomic refcnt update synchronization X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 02 Sep 2016 05:25:14 -0000 From: 李林哲 chagne atomic ref update to always call atomic_add when mbuf is allocated by cpu1 and freed by cpu2. cpu1 cache may not be updated by such a set operation. causes refcnt reads incorrect values. --- lib/librte_mbuf/rte_mbuf.h | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h index 7ea66ed..63e6588 100644 --- a/lib/librte_mbuf/rte_mbuf.h +++ b/lib/librte_mbuf/rte_mbuf.h @@ -786,7 +786,7 @@ struct rte_mbuf { */ union { rte_atomic16_t refcnt_atomic; /**< Atomically accessed refcnt */ - uint16_t refcnt; /**< Non-atomically accessed refcnt */ + volatile uint16_t refcnt; /**< Non-atomically accessed refcnt */ }; uint8_t nb_segs; /**< Number of segments. */ uint8_t port; /**< Input port. */ @@ -1060,16 +1060,12 @@ static inline uint16_t rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value) { /* - * The atomic_add is an expensive operation, so we don't want to - * call it in the case where we know we are the uniq holder of - * this mbuf (i.e. ref_cnt == 1). Otherwise, an atomic - * operation has to be used because concurrent accesses on the - * reference counter can occur. + * This shell always call atomic_add + * + * when mbuf is allocated by cpu1 and freed by cpu2. cpu1 cache may not be updated by such a set operation. + * causes refcnt reads incorrect values + * */ - if (likely(rte_mbuf_refcnt_read(m) == 1)) { - rte_mbuf_refcnt_set(m, 1 + value); - return 1 + value; - } return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value)); } -- 2.7.0.rc2