From: Jeaho Hwang <jhhwang@rtst.co.kr>
To: Peter Chen <peter.chen@kernel.org>
Cc: linux-usb@vger.kernel.org,
"변무광(Byeon Moo Kwang)/자동화연)Automation Platform연구팀"
<mkbyeon@lselectric.co.kr>, "Linux team" <team-linux@rtst.co.kr>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Chipidea USB device goes infinite loop due to interrupt while hw_ep_prime
Date: Wed, 4 Aug 2021 11:03:44 +0900 [thread overview]
Message-ID: <CAJk_X9gwa+4CZRemKqW7XZzxd438EQHA-Ngp4MdmPVgHM0Q5fg@mail.gmail.com> (raw)
In-Reply-To: <20210804013252.GA16420@nchen>
Hi. linux-usb and linux-rt experts.
>
> On 21-08-02 17:35:01, Jeaho Hwang wrote:
> > Hi.
> >
> > We found an infinite loop inside the function hw_ep_set_halt
> > (drivers/usb/chipidea/udc.c) if a cablle is repeatedly
> > connnected/disconnected while ping through RNDIS with chipidea USB device.
> >
> > Using ftrace tracing, we found that hw_ep_set_halt is called due to error
> > return of hw_ep_prime(drivers/usb/chipidea/udc.c:202) which is called from
> > isr_tr_complete_handler -> isr_setup_status_phase -> _ep_queue.
> >
> > The comment of function hw_ep_prime says (execute without interruption) but
> > timer interrupt is occurred while hw_ep_prime is executing. We believe that
> > the interrupt causes an error return of hw_ep_prime. We tried to protect
> > hw_ep_prime from irqs and then no case of the infinite loop is occurred.
> >
> > I want ask if it is appropriate way that turning off irq inside (threaded)
> > irq handlers. And should we explicitly turn off irqs before calling
> > hw_ep_prime?
> >
>
> Jeaho, do you use RT-Linux or standard Linux? The function hw_ep_prime is
> only called at udc_irq which is registered as top-half irq handlers.
> Why the timer interrupt is occurred when hw_ep_prime is executing?
We use preempt_RT so timer interrupt could be occurred. Now I found
out that forced threaded irq handler disables local irq on standard
linux so It is a linux-rt issue. Then should I make patch which
disables local irqs during hw_ep_prime for RT kernel and suggest it to
linux-rt maintainers?
Thanks for a kind answer Peter.
>
> --
>
> Thanks,
> Peter Chen
>
--
황재호, Jay Hwang, linux team manager of RTst
010-7242-1593
next prev parent reply other threads:[~2021-08-04 2:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAJk_X9hBB_edByfEvueSyWgKjpYGZbS2rPLPCSpRrPr+icFz_Q@mail.gmail.com>
2021-08-04 1:32 ` Chipidea USB device goes infinite loop due to interrupt while hw_ep_prime Peter Chen
2021-08-04 2:03 ` Jeaho Hwang [this message]
2021-08-09 1:27 ` Peter Chen
2021-08-09 1:45 ` Jeaho Hwang
2021-08-09 6:31 ` Peter Chen
2021-08-04 3:11 ` Jeaho Hwang
2021-08-09 1:40 ` Peter Chen
2021-08-02 8:38 Jeaho Hwang
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