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Date: Wed, 8 Oct 2014 13:54:07 +0300
From: Octavian Purdila <octavian.purdila@...el.com>
To: Johan Hovold <johan@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Linus Walleij <linus.walleij@...aro.org>,
Alexandre Courbot <gnurou@...il.com>,
Wolfram Sang <wsa@...-dreams.de>,
Samuel Ortiz <sameo@...ux.intel.com>,
Lee Jones <lee.jones@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
Daniel Baluta <daniel.baluta@...el.com>,
Laurentiu Palcu <laurentiu.palcu@...el.com>,
linux-usb@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
linux-i2c@...r.kernel.org
Subject: Re: [PATCH v6 1/4] mfd: add support for Diolan DLN-2 devices
On Wed, Oct 8, 2014 at 12:23 PM, Johan Hovold <johan@...nel.org> wrote:
> On Thu, Sep 25, 2014 at 07:07:31PM +0300, Octavian Purdila wrote:
>
>> +static void dln2_rx_transfer(struct dln2_dev *dln2, struct urb *urb,
>> + u16 handle, u16 rx_slot)
>> +{
>> + struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle];
>> + struct dln2_rx_context *rxc;
>> + struct device *dev = &dln2->interface->dev;
>> +
>> + spin_lock(&rxs->lock);
>
> You must use spin_lock_irqsave here as you call it from the completion
> handler.
Why? AFAICS the completion handler gets called from the HCD irq handler:
[ 2.503945] Call Trace:
[ 2.503945] <IRQ> [<ffffffff81a73d14>] dump_stack+0x4e/0x7a
[ 2.503945] [<ffffffff81639fcb>] dln2_rx+0x1eb/0x2d0
[ 2.503945] [<ffffffff81742202>] __usb_hcd_giveback_urb+0x72/0x120
[ 2.503945] [<ffffffff817423cf>] usb_hcd_giveback_urb+0x3f/0x120
[ 2.503945] [<ffffffff81786ffa>] uhci_giveback_urb+0xaa/0x290
[ 2.503945] [<ffffffff811d36d7>] ? dma_pool_free+0xa7/0xd0
[ 2.503945] [<ffffffff81788fe3>] uhci_scan_schedule+0x493/0xb20
[ 2.503945] [<ffffffff81789c9e>] uhci_irq+0x9e/0x180
[ 2.503945] [<ffffffff81741546>] usb_hcd_irq+0x26/0x40
[ 2.503945] [<ffffffff8110e46e>] handle_irq_event_percpu+0x3e/0x1e0
[ 2.503945] [<ffffffff8110e64d>] handle_irq_event+0x3d/0x60
[ 2.503945] [<ffffffff811117f9>] handle_fasteoi_irq+0x99/0x160
[ 2.503945] [<ffffffff810492c2>] handle_irq+0x102/0x190
[ 2.503945] [<ffffffff810e493a>] ? atomic_notifier_call_chain+0x3a/0x50
[ 2.503945] [<ffffffff81a7fbcb>] do_IRQ+0x5b/0x100
[ 2.503945] [<ffffffff81a7dd6f>] common_interrupt+0x6f/0x6f
[ 2.503945] <EOI> [<ffffffff810512ed>] ? default_idle+0x1d/0x100
>
>> +
>> + rxc = &rxs->slots[rx_slot];
>> +
>> + if (rxc->in_use && !rxc->urb) {
>> + rxc->urb = urb;
>> + complete(&rxc->done);
>> + /* URB will be resubmitted in free_rx_slot */
>> + } else {
>> + dev_warn(dev, "bad/late response %d/%d\n", handle, rx_slot);
>> + dln2_submit_urb(dln2, urb, GFP_ATOMIC);
>> + }
>> +
>> + spin_unlock(&rxs->lock);
>> +}
>
>> +static int _dln2_transfer(struct dln2_dev *dln2, u16 handle, u16 cmd,
>> + const void *obuf, unsigned obuf_len,
>> + void *ibuf, unsigned *ibuf_len)
>> +{
>> + int ret = 0;
>> + u16 result;
>> + int rx_slot;
>> + struct dln2_response *rsp;
>> + struct dln2_rx_context *rxc;
>> + struct device *dev;
>> + const int timeout = DLN2_USB_TIMEOUT * HZ / 1000;
>> + struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle];
>> +
>> + spin_lock(&dln2->disconnect_lock);
>
> How did you test this version? You never initialise disconnect_lock so
> lockdep complains loudly when calling _dln2_transfer during probe.
>
Oops, missed that as lockdep was not enable in the lastest test setup.
>> + if (!dln2->disconnect)
>> + dln2->active_transfers++;
>> + else
>> + ret = -ENODEV;
>> + spin_unlock(&dln2->disconnect_lock);
>> +
>> + if (ret)
>> + return ret;
>> +
>> + rx_slot = alloc_rx_slot(dln2, handle);
>> + if (rx_slot < 0) {
>> + ret = rx_slot;
>> + goto out_decr;
>> + }
>> +
>> + dev = &dln2->interface->dev;
>> +
>> + ret = dln2_send_wait(dln2, handle, cmd, rx_slot, obuf, obuf_len);
>> + if (ret < 0) {
>> + dev_err(dev, "USB write failed: %d\n", ret);
>> + goto out_free_rx_slot;
>> + }
>> +
>> + rxc = &rxs->slots[rx_slot];
>> +
>> + ret = wait_for_completion_interruptible_timeout(&rxc->done, timeout);
>> + if (ret <= 0) {
>> + if (!ret)
>> + ret = -ETIMEDOUT;
>> + goto out_free_rx_slot;
>> + }
>> +
>> + if (!rxc->urb) {
>> + ret = -ENODEV;
>> + goto out_free_rx_slot;
>> + }
>> +
>> + /* if we got here we know that the response header has been checked */
>> + rsp = rxc->urb->transfer_buffer;
>> +
>> + if (rsp->hdr.size < sizeof(*rsp)) {
>> + ret = -EPROTO;
>> + goto out_free_rx_slot;
>> + }
>> +
>> + result = le16_to_cpu(rsp->result);
>> + if (result) {
>> + dev_dbg(dev, "%d received response with error %d\n",
>> + handle, result);
>> + ret = -EREMOTEIO;
>> + goto out_free_rx_slot;
>> + }
>> +
>> + if (!ibuf) {
>> + ret = 0;
>> + goto out_free_rx_slot;
>> + }
>> +
>> + if (*ibuf_len > rsp->hdr.size - sizeof(*rsp))
>> + *ibuf_len = rsp->hdr.size - sizeof(*rsp);
>> +
>> + memcpy(ibuf, rsp + 1, *ibuf_len);
>> +
>> +out_free_rx_slot:
>> + free_rx_slot(dln2, handle, rx_slot);
>> +out_decr:
>> + spin_lock(&dln2->disconnect_lock);
>> + dln2->active_transfers--;
>> + spin_unlock(&dln2->disconnect_lock);
>> + if (dln2->disconnect)
>> + wake_up(&dln2->disconnect_wq);
>> +
>> + return ret;
>> +}
>
>> +static void dln2_disconnect(struct usb_interface *interface)
>> +{
>> + struct dln2_dev *dln2 = usb_get_intfdata(interface);
>> + int i, j;
>> +
>> + /* don't allow starting new transfers */
>> + spin_lock(&dln2->disconnect_lock);
>> + dln2->disconnect = true;
>> + spin_unlock(&dln2->disconnect_lock);
>> +
>> + /* cancel in progress transfers */
>> + for (i = 0; i < DLN2_HANDLES; i++) {
>> + struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[i];
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&rxs->lock, flags);
>
> Just stick to spin_lock in this function.
>
AFAICS disconnect is called from a kernel thread. Are there guarantees
that we can't get a call to the completion routine while we are
running it?
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