From: Felipe Balbi <balbi@kernel.org>
To: Alexandru Ardelean <alexandru.ardelean@analog.com>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: gregkh@linuxfoundation.org, bigeasy@linutronix.de,
Lars-Peter Clausen <lars@metafoo.de>,
Michael Olbrich <m.olbrich@pengutronix.de>,
Alexandru Ardelean <alexandru.ardelean@analog.com>
Subject: Re: [PATCH][RESEND] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully
Date: Thu, 30 Jan 2020 14:02:05 +0200 [thread overview]
Message-ID: <87d0b1885e.fsf@kernel.org> (raw)
In-Reply-To: <20200116132459.22383-1-alexandru.ardelean@analog.com>
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Hi,
Alexandru Ardelean <alexandru.ardelean@analog.com> writes:
> From: Lars-Peter Clausen <lars@metafoo.de>
>
> Trying to dequeue and URB that is currently not queued should be a no-op
> and be handled gracefully.
>
> Use the list field of the URB to indicate whether it is queued or not by
> setting it to the empty list when it is not queued.
>
> Handling this gracefully allows for race condition free synchronization
> between the complete callback being called to to a completed transfer and
> trying to call usb_ep_dequeue() at the same time.
We need a little more information here. Can you further explain what
happens and how you caught this?
> Tested-by: Michael Olbrich <m.olbrich@pengutronix.de>
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>
> * Added Michael Olbrich's Tested-by tag
> https://lore.kernel.org/linux-usb/20191112144108.GA1859@pengutronix.de/
>
> drivers/usb/dwc3/gadget.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 1b8014ab0b25..22a78eb41a5b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -177,7 +177,7 @@ static void dwc3_gadget_del_and_unmap_request(struct dwc3_ep *dep,
> {
> struct dwc3 *dwc = dep->dwc;
>
> - list_del(&req->list);
> + list_del_init(&req->list);
this should *not* be necessary. Neither the INIT_LIST_HEAD() below.
> req->remaining = 0;
> req->needs_extra_trb = false;
>
> @@ -847,6 +847,7 @@ static struct usb_request *dwc3_gadget_ep_alloc_request(struct usb_ep *ep,
> req->epnum = dep->number;
> req->dep = dep;
> req->status = DWC3_REQUEST_STATUS_UNKNOWN;
> + INIT_LIST_HEAD(&req->list);
>
> trace_dwc3_alloc_request(req);
>
> @@ -1549,6 +1550,10 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
>
> spin_lock_irqsave(&dwc->lock, flags);
>
> + /* Not queued, nothing to do */
> + if (list_empty(&req->list))
> + goto out0;
The loop below is actually looking for the request in our lists. You
just made the entire loop below unnecessary, but you didn't change it
accordingly. Moreover, I think that a user dequeueing a request that
wasn't queued for the current endpoint indicates a possible bug in the
gadget driver which needs to be fixed.
If you really disagree, suffice to change "ret = -EINVAL;" to "ret =
0;" and you would get what you want, without any of the extra cruft.
cheers
--
balbi
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next prev parent reply other threads:[~2020-01-30 12:02 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 14:45 [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully Alexandru Ardelean
2019-11-12 14:41 ` Michael Olbrich
2020-01-16 11:12 ` Ardelean, Alexandru
2020-01-16 13:05 ` Felipe Balbi
2020-01-16 13:24 ` [PATCH][RESEND] " Alexandru Ardelean
2020-01-30 12:02 ` Felipe Balbi [this message]
2020-03-10 13:22 ` Ardelean, Alexandru
2020-03-10 13:45 ` Lars-Peter Clausen
2020-03-10 14:07 ` Lars-Peter Clausen
2020-03-27 8:43 ` [PATCH] usb: dwc3: gadget: don't dequeue requests on already disabled endpoints Michael Grzeschik
2020-03-27 8:53 ` Sergei Shtylyov
2020-03-27 11:15 ` Andy Shevchenko
2020-03-27 9:14 ` Lars-Peter Clausen
2020-03-27 10:43 ` Michael Grzeschik
2020-03-27 10:55 ` Lars-Peter Clausen
2020-03-28 8:27 ` Felipe Balbi
2020-03-29 19:02 ` Michael Grzeschik
2020-03-30 7:18 ` Felipe Balbi
2020-03-30 8:25 ` Michael Grzeschik
2020-03-30 10:06 ` Felipe Balbi
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