From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D6B26BA33 for ; Wed, 18 Oct 2023 13:56:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="W4rN6w50" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3F3FC433C7; Wed, 18 Oct 2023 13:56:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697637391; bh=3xuMI2XSHdB7MQa/Nb1GICGAiTx+7oCtl/hm1V9rKnM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=W4rN6w50t3vVYH5Wf0wVVAUqV+V40rEdmNTmzhDdkUkOoG4I4f/h5y4mBoBMgV1T7 5E2QKF9LG5cZLSynBif/eeeRxC+eE0BLRXOBvEXWnPnDjspWeqFdUCFgwu9ioHk7Vy PEAb3zpq40XxZW7tqRr5MALw6iwVIpjoFDnT9pLIfiHzRBewoWzh2Ny/5oZ66m1/zq +nukqIY5iZLFTpnm4hPgcIc6dOnaB5Zb4PfnAl+RYp6VhlbDE0wvaKmm2VHnrGTgG8 Ml7Lg79FW02asoANLAbxbxExIVnHq7/TFAnJIo/+o+FcNF/1fxtR/G1pnD7kSv/P/7 /Co80hQ58tPVQ== Date: Wed, 18 Oct 2023 15:56:28 +0200 From: Simon Horman To: Mirsad Todorovac Cc: Heiner Kallweit , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, nic_swsd@realtek.com, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Marco Elver Subject: Re: [PATCH v2 3/3] r8169: fix the KCSAN reported data-race in rtl_tx while reading TxDescArray[entry].opts1 Message-ID: <20231018135628.GQ1940501@kernel.org> References: <20231016214753.175097-1-mirsad.todorovac@alu.unizg.hr> <20231016214753.175097-3-mirsad.todorovac@alu.unizg.hr> <20231017200138.GB1940501@kernel.org> <992dcaf7-2b24-4e91-8c69-a5471da209ae@alu.unizg.hr> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <992dcaf7-2b24-4e91-8c69-a5471da209ae@alu.unizg.hr> On Tue, Oct 17, 2023 at 10:43:36PM +0200, Mirsad Todorovac wrote: > On 10/17/23 22:01, Simon Horman wrote: > > On Mon, Oct 16, 2023 at 11:47:56PM +0200, Mirsad Goran Todorovac wrote: > > > KCSAN reported the following data-race: > > > > > > ================================================================== > > > BUG: KCSAN: data-race in rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4368 drivers/net/ethernet/realtek/r8169_main.c:4581) r8169 > > > > > > race at unknown origin, with read to 0xffff888140d37570 of 4 bytes by interrupt on cpu 21: > > > rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4368 drivers/net/ethernet/realtek/r8169_main.c:4581) r8169 > > > __napi_poll (net/core/dev.c:6527) > > > net_rx_action (net/core/dev.c:6596 net/core/dev.c:6727) > > > __do_softirq (kernel/softirq.c:553) > > > __irq_exit_rcu (kernel/softirq.c:427 kernel/softirq.c:632) > > > irq_exit_rcu (kernel/softirq.c:647) > > > sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1074 (discriminator 14)) > > > asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:645) > > > cpuidle_enter_state (drivers/cpuidle/cpuidle.c:291) > > > cpuidle_enter (drivers/cpuidle/cpuidle.c:390) > > > call_cpuidle (kernel/sched/idle.c:135) > > > do_idle (kernel/sched/idle.c:219 kernel/sched/idle.c:282) > > > cpu_startup_entry (kernel/sched/idle.c:378 (discriminator 1)) > > > start_secondary (arch/x86/kernel/smpboot.c:210 arch/x86/kernel/smpboot.c:294) > > > secondary_startup_64_no_verify (arch/x86/kernel/head_64.S:433) > > > > > > value changed: 0xb0000042 -> 0x00000000 > > > > > > Reported by Kernel Concurrency Sanitizer on: > > > CPU: 21 PID: 0 Comm: swapper/21 Tainted: G L 6.6.0-rc2-kcsan-00143-gb5cbe7c00aa0 #41 > > > Hardware name: ASRock X670E PG Lightning/X670E PG Lightning, BIOS 1.21 04/26/2023 > > > ================================================================== > > > > > > The read side is in > > > > > > drivers/net/ethernet/realtek/r8169_main.c > > > ========================================= > > > 4355 static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp, > > > 4356 int budget) > > > 4357 { > > > 4358 unsigned int dirty_tx, bytes_compl = 0, pkts_compl = 0; > > > 4359 struct sk_buff *skb; > > > 4360 > > > 4361 dirty_tx = tp->dirty_tx; > > > 4362 > > > 4363 while (READ_ONCE(tp->cur_tx) != dirty_tx) { > > > 4364 unsigned int entry = dirty_tx % NUM_TX_DESC; > > > 4365 u32 status; > > > 4366 > > > → 4367 status = le32_to_cpu(tp->TxDescArray[entry].opts1); > > > 4368 if (status & DescOwn) > > > 4369 break; > > > 4370 > > > 4371 skb = tp->tx_skb[entry].skb; > > > 4372 rtl8169_unmap_tx_skb(tp, entry); > > > 4373 > > > 4374 if (skb) { > > > 4375 pkts_compl++; > > > 4376 bytes_compl += skb->len; > > > 4377 napi_consume_skb(skb, budget); > > > 4378 } > > > 4379 dirty_tx++; > > > 4380 } > > > 4381 > > > 4382 if (tp->dirty_tx != dirty_tx) { > > > 4383 dev_sw_netstats_tx_add(dev, pkts_compl, bytes_compl); > > > 4384 WRITE_ONCE(tp->dirty_tx, dirty_tx); > > > 4385 > > > 4386 netif_subqueue_completed_wake(dev, 0, pkts_compl, bytes_compl, > > > 4387 rtl_tx_slots_avail(tp), > > > 4388 R8169_TX_START_THRS); > > > 4389 /* > > > 4390 * 8168 hack: TxPoll requests are lost when the Tx packets are > > > 4391 * too close. Let's kick an extra TxPoll request when a burst > > > 4392 * of start_xmit activity is detected (if it is not detected, > > > 4393 * it is slow enough). -- FR > > > 4394 * If skb is NULL then we come here again once a tx irq is > > > 4395 * triggered after the last fragment is marked transmitted. > > > 4396 */ > > > 4397 if (READ_ONCE(tp->cur_tx) != dirty_tx && skb) > > > 4398 rtl8169_doorbell(tp); > > > 4399 } > > > 4400 } > > > > > > tp->TxDescArray[entry].opts1 is reported to have a data-race and READ_ONCE() fixes > > > this KCSAN warning. > > > > > > 4366 > > > → 4367 status = le32_to_cpu(READ_ONCE(tp->TxDescArray[entry].opts1)); > > > 4368 if (status & DescOwn) > > > 4369 break; > > > 4370 > > > > > > Fixes: ^1da177e4c3f4 ("initial git repository build") > > > > Hi Mirsad, > > > > The fixes tag above seems wrong. > > Hi, Simon, > > It is taken directly from "git blame" as you can check for yourself. > > It is supposed to tag the commits prior to the introduction of git. > > If you have a better idea how to denote those, I will be happy to learn, > but I have no better clue than what "git blame" gives ... Interesting, thanks for the explanation. I do think it's more usual, in such cases, to use the following. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Best regards, > Mirsad Todorovac > > > Cc: Heiner Kallweit > > > Cc: nic_swsd@realtek.com > > > Cc: "David S. Miller" > > > Cc: Eric Dumazet > > > Cc: Jakub Kicinski > > > Cc: Paolo Abeni > > > Cc: Marco Elver > > > Cc: netdev@vger.kernel.org > > > Link: https://lore.kernel.org/lkml/dc7fc8fa-4ea4-e9a9-30a6-7c83e6b53188@alu.unizg.hr/ > > > Signed-off-by: Mirsad Goran Todorovac > > > Acked-by: Marco Elver > > > > ... >