From patchwork Fri Nov 12 10:24:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavan Kondeti X-Patchwork-Id: 12616503 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F4B1C433F5 for ; Fri, 12 Nov 2021 10:24:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC42A61027 for ; Fri, 12 Nov 2021 10:24:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234840AbhKLK1n (ORCPT ); Fri, 12 Nov 2021 05:27:43 -0500 Received: from alexa-out.qualcomm.com ([129.46.98.28]:27663 "EHLO alexa-out.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234675AbhKLK1n (ORCPT ); Fri, 12 Nov 2021 05:27:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1636712693; x=1668248693; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=fDOkLGbgQhRqFwakm+NiboZGirvpttu4kgf0KFtHkR4=; b=QNBFrHMuk6ElOaBopMNzCXjy1Z+NsvTIg5l6KTPZEXIf5LJbI1sD3emW Bt6sYlnDXwMiMcskLfCg6u3HLQzB9Ezb73+GQ/f2dmIhUeUcl8dohSJSc zb/ap3s5Pyk+5WGJ/5PgOwM8ZH3kWzfX3jRQWHSF+4wMeBjQsGv+ZAO7y 0=; Received: from ironmsg08-lv.qualcomm.com ([10.47.202.152]) by alexa-out.qualcomm.com with ESMTP; 12 Nov 2021 02:24:53 -0800 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg08-lv.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2021 02:24:51 -0800 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.922.19; Fri, 12 Nov 2021 02:24:51 -0800 Received: from quicinc.com (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.922.19; Fri, 12 Nov 2021 02:24:47 -0800 From: Pavankumar Kondeti To: , CC: Pavankumar Kondeti , Felipe Balbi , Greg Kroah-Hartman , "Jens Axboe" , Jack Pham , Peter Chen , kernel test robot , Wei Ming Chen , "Gustavo A. R. Silva" , Dean Anderson , Andrew Gabbasov Subject: [PATCH v3] usb: gadget: f_fs: Use stream_open() for endpoint files Date: Fri, 12 Nov 2021 15:54:40 +0530 Message-ID: <1636712682-1226-1-git-send-email-quic_pkondeti@quicinc.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nalasex01a.na.qualcomm.com (10.47.209.196) Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Function fs endpoint file operations are synchronized via an interruptible mutex wait. However we see threads that do ep file operations concurrently are getting blocked for the mutex lock in __fdget_pos(). This is an uninterruptible wait and we see hung task warnings and kernel panic if hung_task_panic systcl is enabled if host does not send/receive the data for long time. The reason for threads getting blocked in __fdget_pos() is due to the file position protection introduced by the commit 9c225f2655e3 ("vfs: atomic f_pos accesses as per POSIX"). Since function fs endpoint files does not have the notion of the file position, switch to the stream mode. This will bypass the file position mutex and threads will be blocked in interruptible state for the function fs mutex. It should not affects user space as we are only changing the task state changes the task state from UNINTERRUPTIBLE to INTERRUPTIBLE while waiting for the USB transfers to be finished. However there is a slight change to the O_NONBLOCK behavior. Earlier threads that are using O_NONBLOCK are also getting blocked inside fdget_pos(). Now they reach to function fs and error code is returned. The non blocking behavior is actually honoured now. Signed-off-by: Pavankumar Kondeti Reviewed-by: John Keeping --- v3: - Added more background and user space impact in the commit description v2: - Removed Change-Id tag drivers/usb/gadget/function/f_fs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index e20c19a..3c584da 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -614,7 +614,7 @@ static int ffs_ep0_open(struct inode *inode, struct file *file) file->private_data = ffs; ffs_data_opened(ffs); - return 0; + return stream_open(inode, file); } static int ffs_ep0_release(struct inode *inode, struct file *file) @@ -1154,7 +1154,7 @@ ffs_epfile_open(struct inode *inode, struct file *file) file->private_data = epfile; ffs_data_opened(epfile->ffs); - return 0; + return stream_open(inode, file); } static int ffs_aio_cancel(struct kiocb *kiocb)