From patchwork Fri Jun 28 09:07:50 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 2797741 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id C614B9F3C3 for ; Fri, 28 Jun 2013 09:10:37 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3313C20173 for ; Fri, 28 Jun 2013 09:10:36 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 772C120172 for ; Fri, 28 Jun 2013 09:10:33 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UsUg0-0007gA-Pv; Fri, 28 Jun 2013 09:09:09 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UsUfh-0007dw-5I; Fri, 28 Jun 2013 09:08:49 +0000 Received: from mail-pb0-f52.google.com ([209.85.160.52]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UsUfb-0007cd-85 for linux-arm-kernel@lists.infradead.org; Fri, 28 Jun 2013 09:08:45 +0000 Received: by mail-pb0-f52.google.com with SMTP id xa12so2025351pbc.25 for ; Fri, 28 Jun 2013 02:08:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; bh=z/PctL4JoZ6Tkt80Y51pVt8r3QCldriW9YD0pEhzLhU=; b=esk5X7ZCv9iMUlPzKVPZY+IENWhCosMk9SRFkRmO0G0l61gNO0pu+PD9G9nCxxZMjV 6qS41cR9oKPr+1Z1n93j7NIl/3OQza6BTzNwdu+98yUrBSaDsn3b54Cz1h4wJYrlHo9Q eQ7eiICRZ9eQJ89SbB2iVP618ECyEiE0cZrEzg0VIt0qONFKc9BB/7pbVhKn37IemrEI 2P2+gqGaTIdqhI5xjNbQth+BJ2bQ/BqLqEJjdSzqptIYAmNVTZYeyERXkMk11ZmEBbD9 /hWF6t0EG6PAHtuOqSWN6h0lH4b88J0W5xOcWBvml/ILLoyFG9XotrHs0U+cEITYBP/S jCrw== X-Received: by 10.68.224.228 with SMTP id rf4mr10479872pbc.50.1372410500751; Fri, 28 Jun 2013 02:08:20 -0700 (PDT) Received: from localhost ([183.37.203.121]) by mx.google.com with ESMTPSA id fm2sm8000870pab.13.2013.06.28.02.08.13 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 28 Jun 2013 02:08:19 -0700 (PDT) From: Ming Lei To: Greg Kroah-Hartman Subject: [PATCH v3 1/4] USB: HCD: support giveback of URB in tasklet context Date: Fri, 28 Jun 2013 17:07:50 +0800 Message-Id: <1372410473-30920-2-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1372410473-30920-1-git-send-email-ming.lei@canonical.com> References: <1372410473-30920-1-git-send-email-ming.lei@canonical.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130628_050843_581665_1F36A074 X-CRM114-Status: GOOD ( 30.04 ) X-Spam-Score: -2.6 (--) Cc: Oliver Neukum , Ming Lei , linux-usb@vger.kernel.org, Steven Rostedt , Alan Stern , Thomas Gleixner , linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-5.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This patch implements the mechanism of giveback of URB in tasklet context, so that hardware interrupt handling time for usb host controller can be saved much, and HCD interrupt handling can be simplified. Motivations: 1), on some arch(such as ARM), DMA mapping/unmapping is a bit time-consuming, for example: when accessing usb mass storage via EHCI on pandaboard, the common length of transfer buffer is 120KB, the time consumed on DMA unmapping may reach hundreds of microseconds; even on A15 based box, the time is still about scores of microseconds 2), on some arch, reading DMA coherent memoery is very time-consuming, the most common example is usb video class driver[1] 3), driver's complete() callback may do much things which is driver specific, so the time is consumed unnecessarily in hardware irq context. 4), running driver's complete() callback in hardware irq context causes that host controller driver has to release its lock in interrupt handler, so reacquiring the lock after return may busy wait a while and increase interrupt handling time. More seriously, releasing the HCD lock makes HCD becoming quite complicated to deal with introduced races. So the patch proposes to run giveback of URB in tasklet context, then time consumed in HCD irq handling doesn't depend on drivers' complete and DMA mapping/unmapping any more, also we can simplify HCD since the HCD lock isn't needed to be released during irq handling. The patch should be reasonable and doable: 1), for drivers, they don't care if the complete() is called in hard irq context or softirq context 2), the biggest change is the situation in which usb_submit_urb() is called in complete() callback, so the introduced tasklet schedule delay might be a con, but it shouldn't be a big deal: - control/bulk asynchronous transfer isn't sensitive to schedule delay - the patch schedules giveback of periodic URBs using tasklet_hi_schedule, so the introduced delay should be very small - for ISOC transfer, generally, drivers submit several URBs concurrently to avoid interrupt delay, so it is OK with the little schedule delay. - for interrupt transfer, generally, drivers only submit one URB at the same time, but interrupt transfer is often used in event report, polling, ... situations, and a little delay should be OK. Considered that HCDs may optimize on submitting URB in complete(), the patch may cause the optimization not working, so introduces one flag to mark if the HCD supports to run giveback URB in tasklet context. When all HCDs are ready, the flag can be removed. [1], http://marc.info/?t=136438111600010&r=1&w=2 Cc: Oliver Neukum Cc: Alan Stern Signed-off-by: Ming Lei --- drivers/usb/core/hcd.c | 147 +++++++++++++++++++++++++++++++++++++---------- include/linux/usb/hcd.h | 17 ++++++ 2 files changed, 134 insertions(+), 30 deletions(-) diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index d53547d..b851c88 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -669,15 +669,7 @@ error: /* any errors get returned through the urb completion */ spin_lock_irq(&hcd_root_hub_lock); usb_hcd_unlink_urb_from_ep(hcd, urb); - - /* This peculiar use of spinlocks echoes what real HC drivers do. - * Avoiding calls to local_irq_disable/enable makes the code - * RT-friendly. - */ - spin_unlock(&hcd_root_hub_lock); usb_hcd_giveback_urb(hcd, urb, status); - spin_lock(&hcd_root_hub_lock); - spin_unlock_irq(&hcd_root_hub_lock); return 0; } @@ -717,9 +709,7 @@ void usb_hcd_poll_rh_status(struct usb_hcd *hcd) memcpy(urb->transfer_buffer, buffer, length); usb_hcd_unlink_urb_from_ep(hcd, urb); - spin_unlock(&hcd_root_hub_lock); usb_hcd_giveback_urb(hcd, urb, 0); - spin_lock(&hcd_root_hub_lock); } else { length = 0; set_bit(HCD_FLAG_POLL_PENDING, &hcd->flags); @@ -809,10 +799,7 @@ static int usb_rh_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status) if (urb == hcd->status_urb) { hcd->status_urb = NULL; usb_hcd_unlink_urb_from_ep(hcd, urb); - - spin_unlock(&hcd_root_hub_lock); usb_hcd_giveback_urb(hcd, urb, status); - spin_lock(&hcd_root_hub_lock); } } done: @@ -1623,6 +1610,72 @@ int usb_hcd_unlink_urb (struct urb *urb, int status) /*-------------------------------------------------------------------------*/ +static void __usb_hcd_giveback_urb(struct urb *urb) +{ + struct usb_hcd *hcd = bus_to_hcd(urb->dev->bus); + int status = urb->unlinked; + unsigned long flags; + + urb->hcpriv = NULL; + if (unlikely((urb->transfer_flags & URB_SHORT_NOT_OK) && + urb->actual_length < urb->transfer_buffer_length && + !status)) + status = -EREMOTEIO; + + unmap_urb_for_dma(hcd, urb); + usbmon_urb_complete(&hcd->self, urb, status); + usb_unanchor_urb(urb); + + /* pass ownership to the completion handler */ + urb->status = status; + + /* + * We disable local IRQs here avoid possible deadlock because + * drivers may call spin_lock() to hold lock which might be + * acquired in one hard interrupt handler. + * + * The local_irq_save()/local_irq_restore() around complete() + * will be removed if current USB drivers have been cleaned up + * and no one may trigger the above deadlock situation when + * running complete() in tasklet. + */ + local_irq_save(flags); + urb->complete(urb); + local_irq_restore(flags); + + atomic_dec(&urb->use_count); + if (unlikely(atomic_read(&urb->reject))) + wake_up(&usb_kill_urb_queue); + usb_put_urb(urb); +} + +static void usb_giveback_urb_bh(unsigned long param) +{ + struct giveback_urb_bh *bh = (struct giveback_urb_bh *)param; + struct list_head local_list; + + spin_lock_irq(&bh->lock); + bh->running = true; + restart: + list_replace_init(&bh->head, &local_list); + spin_unlock_irq(&bh->lock); + + while (!list_empty(&local_list)) { + struct urb *urb; + + urb = list_entry(local_list.next, struct urb, urb_list); + list_del_init(&urb->urb_list); + __usb_hcd_giveback_urb(urb); + } + + /* check if there are new URBs to giveback */ + spin_lock_irq(&bh->lock); + if (!list_empty(&bh->head)) + goto restart; + bh->running = false; + spin_unlock_irq(&bh->lock); +} + /** * usb_hcd_giveback_urb - return URB from HCD to device driver * @hcd: host controller returning the URB @@ -1642,25 +1695,37 @@ int usb_hcd_unlink_urb (struct urb *urb, int status) */ void usb_hcd_giveback_urb(struct usb_hcd *hcd, struct urb *urb, int status) { - urb->hcpriv = NULL; - if (unlikely(urb->unlinked)) - status = urb->unlinked; - else if (unlikely((urb->transfer_flags & URB_SHORT_NOT_OK) && - urb->actual_length < urb->transfer_buffer_length && - !status)) - status = -EREMOTEIO; + struct giveback_urb_bh *bh; + bool running, high_prio_bh; - unmap_urb_for_dma(hcd, urb); - usbmon_urb_complete(&hcd->self, urb, status); - usb_unanchor_urb(urb); + /* pass status to tasklet via unlinked */ + if (likely(!urb->unlinked)) + urb->unlinked = status; - /* pass ownership to the completion handler */ - urb->status = status; - urb->complete (urb); - atomic_dec (&urb->use_count); - if (unlikely(atomic_read(&urb->reject))) - wake_up (&usb_kill_urb_queue); - usb_put_urb (urb); + if (!hcd_giveback_urb_in_bh(hcd) && !is_root_hub(urb->dev)) { + __usb_hcd_giveback_urb(urb); + return; + } + + if (usb_pipeisoc(urb->pipe) || usb_pipeint(urb->pipe)) { + bh = &hcd->high_prio_bh; + high_prio_bh = true; + } else { + bh = &hcd->low_prio_bh; + high_prio_bh = false; + } + + spin_lock(&bh->lock); + list_add_tail(&urb->urb_list, &bh->head); + running = bh->running; + spin_unlock(&bh->lock); + + if (running) + ; + else if (high_prio_bh) + tasklet_hi_schedule(&bh->bh); + else + tasklet_schedule(&bh->bh); } EXPORT_SYMBOL_GPL(usb_hcd_giveback_urb); @@ -2282,6 +2347,14 @@ EXPORT_SYMBOL_GPL (usb_hc_died); /*-------------------------------------------------------------------------*/ +static void init_giveback_urb_bh(struct giveback_urb_bh *bh) +{ + + spin_lock_init(&bh->lock); + INIT_LIST_HEAD(&bh->head); + tasklet_init(&bh->bh, usb_giveback_urb_bh, (unsigned long)bh); +} + /** * usb_create_shared_hcd - create and initialize an HCD structure * @driver: HC driver that will use this hcd @@ -2545,6 +2618,10 @@ int usb_add_hcd(struct usb_hcd *hcd, && device_can_wakeup(&hcd->self.root_hub->dev)) dev_dbg(hcd->self.controller, "supports USB remote wakeup\n"); + /* initialize tasklets */ + init_giveback_urb_bh(&hcd->high_prio_bh); + init_giveback_urb_bh(&hcd->low_prio_bh); + /* enable irqs just before we start the controller, * if the BIOS provides legacy PCI irqs. */ @@ -2653,6 +2730,16 @@ void usb_remove_hcd(struct usb_hcd *hcd) usb_disconnect(&rhdev); /* Sets rhdev to NULL */ mutex_unlock(&usb_bus_list_lock); + /* + * tasklet_kill() isn't needed here because: + * - driver's disconnect() called from usb_disconnect() should + * make sure its URBs are completed during the disconnect() + * callback + * + * - it is too late to run complete() here since driver may have + * been removed already now + */ + /* Prevent any more root-hub status calls from the timer. * The HCD might still restart the timer (if a port status change * interrupt occurs), but usb_hcd_poll_rh_status() won't invoke diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h index f5f5c7d..295c98b 100644 --- a/include/linux/usb/hcd.h +++ b/include/linux/usb/hcd.h @@ -22,6 +22,7 @@ #ifdef __KERNEL__ #include +#include #define MAX_TOPO_LEVEL 6 @@ -67,6 +68,13 @@ /*-------------------------------------------------------------------------*/ +struct giveback_urb_bh { + bool running; + spinlock_t lock; + struct list_head head; + struct tasklet_struct bh; +}; + struct usb_hcd { /* @@ -139,6 +147,9 @@ struct usb_hcd { resource_size_t rsrc_len; /* memory/io resource length */ unsigned power_budget; /* in mA, 0 = no limit */ + struct giveback_urb_bh high_prio_bh; + struct giveback_urb_bh low_prio_bh; + /* bandwidth_mutex should be taken before adding or removing * any new bus bandwidth constraints: * 1. Before adding a configuration for a new device. @@ -220,6 +231,7 @@ struct hc_driver { #define HCD_USB2 0x0020 /* USB 2.0 */ #define HCD_USB3 0x0040 /* USB 3.0 */ #define HCD_MASK 0x0070 +#define HCD_BH 0x0100 /* URB complete in BH context */ /* called to init HCD and root hub */ int (*reset) (struct usb_hcd *hcd); @@ -360,6 +372,11 @@ struct hc_driver { int (*find_raw_port_number)(struct usb_hcd *, int); }; +static inline int hcd_giveback_urb_in_bh(struct usb_hcd *hcd) +{ + return hcd->driver->flags & HCD_BH; +} + extern int usb_hcd_link_urb_to_ep(struct usb_hcd *hcd, struct urb *urb); extern int usb_hcd_check_unlink_urb(struct usb_hcd *hcd, struct urb *urb, int status);