From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3BF9CECAAD8 for ; Wed, 21 Sep 2022 08:43:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229520AbiIUInp (ORCPT ); Wed, 21 Sep 2022 04:43:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231214AbiIUInk (ORCPT ); Wed, 21 Sep 2022 04:43:40 -0400 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 588177331B; Wed, 21 Sep 2022 01:43:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663749819; x=1695285819; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=GFvWUsBI6PkgCRX8mshboJMjgXfbyH3ZuVvnUjHR6mc=; b=KokexMs7KShv01IpxK7tXJa4xucMjv3MeNSJtjTiKxesQt38PGneh7r1 MyhsI+NbDsoJSIR4Qid/pinXcPSlqSOHJ0Flt3ZBUPkwTztrTmKU0Jj1L wEtChesiWp8EGAj2XEaHbaEqt15SyH52mDLaow07MTMOB1k/Avq6KIeIW I5oVDP53pvYnWcCSTtdVt9r5gAN4XGXPlsGHr6biOtbJymIRamX/87hun OWaci1hlfeFJkBcpiqSkrNbBq867eHQLXM66gdrH8DySqVKOn3nWX7MNV mEsRkSxgxcaUxrqrPtwxuDqWhovyMM91cu812fc9wpYoTctyEbnvC3XP/ Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10476"; a="297540904" X-IronPort-AV: E=Sophos;i="5.93,332,1654585200"; d="scan'208";a="297540904" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2022 01:43:38 -0700 X-IronPort-AV: E=Sophos;i="5.93,332,1654585200"; d="scan'208";a="744872129" Received: from dgonsal1-mobl1.ger.corp.intel.com ([10.252.58.151]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2022 01:43:36 -0700 Date: Wed, 21 Sep 2022 11:43:29 +0300 (EEST) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Sherry Sun cc: "gregkh@linuxfoundation.org" , "jirislaby@kernel.org" , "bhuvanchandra.dv@toradex.com" , "linux-serial@vger.kernel.org" , "linux-kernel@vger.kernel.org" , dl-linux-imx Subject: RE: [PATCH] tty: serial: fsl_lpuart: disable dma rx/tx use flags in lpuart_dma_shutdown In-Reply-To: Message-ID: References: <20220920111703.1532-1-sherry.sun@nxp.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-1239297179-1663749818=:1741" Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1239297179-1663749818=:1741 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Tue, 20 Sep 2022, Sherry Sun wrote: > > > > -----Original Message----- > > From: Ilpo Järvinen > > Sent: 2022年9月20日 20:26 > > To: Sherry Sun > > Cc: gregkh@linuxfoundation.org; jirislaby@kernel.org; > > bhuvanchandra.dv@toradex.com; linux-serial@vger.kernel.org; linux- > > kernel@vger.kernel.org; dl-linux-imx > > Subject: Re: [PATCH] tty: serial: fsl_lpuart: disable dma rx/tx use flags in > > lpuart_dma_shutdown > > > > On Tue, 20 Sep 2022, Sherry Sun wrote: > > > > > lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer can > > > still occur which in turn tries to access dma apis if > > > lpuart_dma_tx_use flag is true. At this point since dma is torn down, > > > these dma apis can abort. Set lpuart_dma_tx_use and the corresponding > > > rx flag lpuart_dma_rx_use to false in lpuart_dma_shutdown so that dmas > > > are not accessed after they are relinquished. > > > > > > Otherwise, when try to kill btattach, kernel may panic. This patch may > > > fix this issue. > > > root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200 > > > ^C[ 90.182296] Internal error: synchronous external abort: 96000210 [#1] > > PREEMPT SMP > > > [ 90.189806] Modules linked in: moal(O) mlan(O) > > > [ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O > > 5.15.32-06136-g34eecdf2f9e4 #37 > > > [ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT) > > > [ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS > > BTYPE=--) > > > [ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60 > > > [ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c > > > [ 90.225237] sp : ffff800013f0bac0 > > > [ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27: > > ffff000008404800 > > > [ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24: > > ffff000008404a00 > > > [ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21: > > 0000000000000000 > > > [ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18: > > 0000000000000000 > > > [ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15: > > 0000000000000000 > > > [ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12: > > 0000000000000040 > > > [ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 : > > ffff000057bcb090 > > > [ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 : > > ffff000008404804 > > > [ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 : > > ffff0000055b3480 > > > [ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 : > > ffff00000559c800 > > > [ 90.299876] Call trace: > > > [ 90.302321] fsl_edma3_disable_request+0x8/0x60 > > > [ 90.306851] lpuart_flush_buffer+0x40/0x160 > > > [ 90.311037] uart_flush_buffer+0x88/0x120 > > > [ 90.315050] tty_driver_flush_buffer+0x20/0x30 > > > [ 90.319496] hci_uart_flush+0x44/0x90 > > > [ 90.323162] +0x34/0x12c > > > [ 90.327253] tty_ldisc_close+0x38/0x70 > > > [ 90.331005] tty_ldisc_release+0xa8/0x190 > > > [ 90.335018] tty_release_struct+0x24/0x8c > > > [ 90.339022] tty_release+0x3ec/0x4c0 > > > [ 90.342593] __fput+0x70/0x234 > > > [ 90.345652] ____fput+0x14/0x20 > > > [ 90.348790] task_work_run+0x84/0x17c > > > [ 90.352455] do_exit+0x310/0x96c > > > [ 90.355688] do_group_exit+0x3c/0xa0 > > > [ 90.359259] __arm64_sys_exit_group+0x1c/0x20 > > > [ 90.363609] invoke_syscall+0x48/0x114 > > > [ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc > > > [ 90.372068] do_el0_svc+0x2c/0x94 > > > [ 90.375379] el0_svc+0x28/0x80 > > > [ 90.378438] el0t_64_sync_handler+0xa8/0x130 > > > [ 90.382711] el0t_64_sync+0x1a0/0x1a4 > > > [ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041) > > > [ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]--- > > > [ 90.397073] note: btattach[503] exited with preempt_count 1 > > > [ 90.402636] Fixing recursive fault but reboot is needed! > > > > > > Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather DMA > > > for Tx") > > > Signed-off-by: Thara Gopinath > > > Signed-off-by: Sherry Sun > > > --- > > > drivers/tty/serial/fsl_lpuart.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/tty/serial/fsl_lpuart.c > > > b/drivers/tty/serial/fsl_lpuart.c index f21915015d67..064bd1f33c21 > > > 100644 > > > --- a/drivers/tty/serial/fsl_lpuart.c > > > +++ b/drivers/tty/serial/fsl_lpuart.c > > > @@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct > > lpuart_port *sport) > > > if (sport->lpuart_dma_rx_use) { > > > del_timer_sync(&sport->lpuart_timer); > > > lpuart_dma_rx_free(&sport->port); > > > + sport->lpuart_dma_rx_use = false; > > > } > > > > > > if (sport->lpuart_dma_tx_use) { > > > @@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct > > lpuart_port *sport) > > > sport->dma_tx_in_progress = false; > > > dmaengine_terminate_all(sport->dma_tx_chan); > > > } > > > + sport->lpuart_dma_tx_use = false; > > > } > > > > > > if (sport->dma_tx_chan) > > > > Isn't it still racy because lpuart_dma_shutdown() is called outside of port's > > lock? > > Hi Ilpo, do you think add the following changes should work for this? > > diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c > index 064bd1f33c21..b3c53935fbc8 100644 > --- a/drivers/tty/serial/fsl_lpuart.c > +++ b/drivers/tty/serial/fsl_lpuart.c > @@ -1768,10 +1768,14 @@ static int lpuart32_startup(struct uart_port *port) > > static void lpuart_dma_shutdown(struct lpuart_port *sport) > { > + unsigned long flags; > + > if (sport->lpuart_dma_rx_use) { > del_timer_sync(&sport->lpuart_timer); > lpuart_dma_rx_free(&sport->port); > + spin_lock_irqsave(&sport->port.lock, flags); > sport->lpuart_dma_rx_use = false; > + spin_unlock_irqrestore(&sport->port.lock, flags); > } > > if (sport->lpuart_dma_tx_use) { > @@ -1780,7 +1784,9 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport) > sport->dma_tx_in_progress = false; > dmaengine_terminate_all(sport->dma_tx_chan); > } > + spin_lock_irqsave(&sport->port.lock, flags); > sport->lpuart_dma_tx_use = false; > + spin_unlock_irqrestore(&sport->port.lock, flags); > } After reading a bit more, I think the original patch is likely fine since shutdown doesn't seem to be racing with flush_buffer. -- i. --8323329-1239297179-1663749818=:1741--