From patchwork Tue Sep 22 10:13:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Neukum X-Patchwork-Id: 11792057 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 52EC2139A for ; Tue, 22 Sep 2020 10:13:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2AC8B239D2 for ; Tue, 22 Sep 2020 10:13:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="XPRf7nmt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726613AbgIVKNz (ORCPT ); Tue, 22 Sep 2020 06:13:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:57238 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726424AbgIVKNy (ORCPT ); Tue, 22 Sep 2020 06:13:54 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1600769632; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc; bh=hLNlwK4aAmxhaviZBEgCNkRcatYwoWqvV4tnyBUTyhM=; b=XPRf7nmtsmeOOSAfhiA8PUQkskgvCH4U88hWGCK3UFf3vOr74eOCXhLwwoK6C60kU7Lf7W b3q0CyVGknC6GF2YP13ijbx9gBPt+pqdN+RaCS3cTiZMQzcy3M++D15dJUCNXFsTgTd8Ky xn5+B8siVj+05y8Nsu+3A4n8k17Y+gM= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E7D46ADAB; Tue, 22 Sep 2020 10:14:28 +0000 (UTC) From: Oliver Neukum To: penguin-kernel@i-love.sakura.ne.jp, bjorn@mork.no, linux-usb@vger.kernel.org Subject: [RFC] fixes for hangs and error reporting in CDC_WDM Date: Tue, 22 Sep 2020 12:13:23 +0200 Message-Id: <20200922101329.14801-1-oneukum@suse.com> X-Mailer: git-send-email 2.16.4 Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Stress testing has shown that CDC-WDM has some issues with hangs and error reporting 1. wakeups are not correctly handled in multhreaded environments 2. unresponsive hardware is not handled 3. errors are not correctly reported. This needs flush() to be implemented. For easier review all squashed together: --- a/drivers/usb/class/cdc-wdm.c +++ b/drivers/usb/class/cdc-wdm.c @@ -58,6 +58,9 @@ MODULE_DEVICE_TABLE (usb, wdm_ids); #define WDM_MAX 16 +/* flush() is uninterruptible, but we cannot wait forever */ +#define WDM_FLUSH_TIMEOUT (30 * HZ) + /* CDC-WMC r1.1 requires wMaxCommand to be "at least 256 decimal (0x100)" */ #define WDM_DEFAULT_BUFSIZE 256 @@ -151,7 +154,7 @@ static void wdm_out_callback(struct urb *urb) kfree(desc->outbuf); desc->outbuf = NULL; clear_bit(WDM_IN_USE, &desc->flags); - wake_up(&desc->wait); + wake_up_all(&desc->wait); } static void wdm_in_callback(struct urb *urb) @@ -393,6 +396,9 @@ static ssize_t wdm_write if (test_bit(WDM_RESETTING, &desc->flags)) r = -EIO; + if (test_bit(WDM_DISCONNECTING, &desc->flags)) + r = -ENODEV; + if (r < 0) { rv = r; goto out_free_mem_pm; @@ -424,6 +430,7 @@ static ssize_t wdm_write if (rv < 0) { desc->outbuf = NULL; clear_bit(WDM_IN_USE, &desc->flags); + wake_up_all(&desc->wait); /* for flush() */ dev_err(&desc->intf->dev, "Tx URB error: %d\n", rv); rv = usb_translate_errors(rv); goto out_free_mem_pm; @@ -583,11 +590,39 @@ static ssize_t wdm_read return rv; } +/* + * The difference to flush is that we wait forever. If you don't like + * that behavior, you need to send a signal. + */ + +static int wdm_fsync(struct file *file, loff_t start, loff_t end, int datasync) +{ + struct wdm_device *desc = file->private_data; + int rv; + + rv = wait_event_interruptible(desc->wait, + !test_bit(WDM_IN_USE, &desc->flags) || + test_bit(WDM_DISCONNECTING, &desc->flags)); + + if (test_bit(WDM_DISCONNECTING, &desc->flags)) + return -ENODEV; + if (rv < 0) + return -EINTR; + + spin_lock_irq(&desc->iuspin); + rv = desc->werr; + desc->werr = 0; + spin_unlock_irq(&desc->iuspin); + + return usb_translate_errors(rv); +} + static int wdm_flush(struct file *file, fl_owner_t id) { struct wdm_device *desc = file->private_data; + int rv; - wait_event(desc->wait, + rv = wait_event_timeout(desc->wait, /* * needs both flags. We cannot do with one * because resetting it would cause a race @@ -595,16 +630,25 @@ static int wdm_flush(struct file *file, fl_owner_t id) * a disconnect */ !test_bit(WDM_IN_USE, &desc->flags) || - test_bit(WDM_DISCONNECTING, &desc->flags)); + test_bit(WDM_DISCONNECTING, &desc->flags), + WDM_FLUSH_TIMEOUT); - /* cannot dereference desc->intf if WDM_DISCONNECTING */ + /* + * to report the correct error. + * This is best effort + * We are inevitably racing with the hardware. + */ if (test_bit(WDM_DISCONNECTING, &desc->flags)) return -ENODEV; - if (desc->werr < 0) - dev_err(&desc->intf->dev, "Error in flush path: %d\n", - desc->werr); + if (!rv) + return -EIO; + + spin_lock_irq(&desc->iuspin); + rv = desc->werr; + desc->werr = 0; + spin_unlock_irq(&desc->iuspin); - return usb_translate_errors(desc->werr); + return usb_translate_errors(rv); } static __poll_t wdm_poll(struct file *file, struct poll_table_struct *wait) @@ -729,6 +773,7 @@ static const struct file_operations wdm_fops = { .owner = THIS_MODULE, .read = wdm_read, .write = wdm_write, + .fsync = wdm_fsync, .open = wdm_open, .flush = wdm_flush,