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 X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FDAAC433E0 for ; Tue, 9 Jun 2020 18:06:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C6D620691 for ; Tue, 9 Jun 2020 18:06:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387495AbgFISGS (ORCPT ); Tue, 9 Jun 2020 14:06:18 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41202 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731897AbgFISFz (ORCPT ); Tue, 9 Jun 2020 14:05:55 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1jiidF-0001oT-1I; Tue, 09 Jun 2020 19:05:53 +0100 Received: from ben by deadeye with local (Exim 4.94) (envelope-from ) id 1jiidE-006VvD-Iq; Tue, 09 Jun 2020 19:05:52 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "David Mosberger" , "Greg Kroah-Hartman" Date: Tue, 09 Jun 2020 19:04:07 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 16/61] drivers: usb: core: Don't disable irqs in usb_sg_wait() during URB submit. In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.85-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: David Mosberger commit 98b74b0ee57af1bcb6e8b2e76e707a71c5ef8ec9 upstream. usb_submit_urb() may take quite long to execute. For example, a single sg list may have 30 or more entries, possibly leading to that many calls to DMA-map pages. This can cause interrupt latency of several hundred micro-seconds. Avoid the problem by releasing the io->lock spinlock and re-enabling interrupts before calling usb_submit_urb(). This opens races with usb_sg_cancel() and sg_complete(). Handle those races by using usb_block_urb() to stop URBs from being submitted after usb_sg_cancel() or sg_complete() with error. Note that usb_unlink_urb() is guaranteed to return -ENODEV if !io->urbs[i]->dev and since the -ENODEV case is already handled, we don't have to check for !io->urbs[i]->dev explicitly. Before this change, reading 512MB from an ext3 filesystem on a USB memory stick showed a throughput of 12 MB/s with about 500 missed deadlines. With this change, reading the same file gave the same throughput but only one or two missed deadlines. Signed-off-by: David Mosberger Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/usb/core/message.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -306,9 +306,10 @@ static void sg_complete(struct urb *urb) */ spin_unlock(&io->lock); for (i = 0, found = 0; i < io->entries; i++) { - if (!io->urbs[i] || !io->urbs[i]->dev) + if (!io->urbs[i]) continue; if (found) { + usb_block_urb(io->urbs[i]); retval = usb_unlink_urb(io->urbs[i]); if (retval != -EINPROGRESS && retval != -ENODEV && @@ -519,12 +520,10 @@ void usb_sg_wait(struct usb_sg_request * int retval; io->urbs[i]->dev = io->dev; - retval = usb_submit_urb(io->urbs[i], GFP_ATOMIC); - - /* after we submit, let completions or cancellations fire; - * we handshake using io->status. - */ spin_unlock_irq(&io->lock); + + retval = usb_submit_urb(io->urbs[i], GFP_NOIO); + switch (retval) { /* maybe we retrying will recover */ case -ENXIO: /* hc didn't queue this one */ @@ -594,8 +593,8 @@ void usb_sg_cancel(struct usb_sg_request for (i = 0; i < io->entries; i++) { int retval; - if (!io->urbs[i]->dev) - continue; + usb_block_urb(io->urbs[i]); + retval = usb_unlink_urb(io->urbs[i]); if (retval != -EINPROGRESS && retval != -ENODEV