Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v2] usb: cdc-wdm: Fix a sleep-in-atomic-context bug in
 service_outstanding_interrupt()
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Jia-Ju Bai <baijiaju1990@gmail.com>
Cc:     gregkh@linuxfoundation.org, johan@kernel.org, bjorn@mork.no,
        mingo@kernel.org, oneukum@suse.com, viro@zeniv.linux.org.uk,
        mark.rutland@arm.com, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20180901081210.16655-1-baijiaju1990@gmail.com>
 <20180911074930.2g6ryk7qe46cijhi@linutronix.de>
From:   Jia-Ju Bai <baijiaju1990@163.com>
Message-ID: <80bf95d7-7485-d74c-2e41-73bd358aa2c6@163.com>
Date:   Tue, 11 Sep 2018 16:25:21 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.0
MIME-Version: 1.0
In-Reply-To: <20180911074930.2g6ryk7qe46cijhi@linutronix.de>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2018/9/11 15:49, Sebastian Andrzej Siewior wrote:
> On 2018-09-01 16:12:10 [+0800], Jia-Ju Bai wrote:
>> wdm_in_callback() is a completion handler function for the USB driver.
>> So it should not sleep. But it calls service_outstanding_interrupt(),
>> which calls usb_submit_urb() with GFP_KERNEL.
> At which point does wdm_in_callback() invoke
> service_outstanding_interrupt()? I don't see it. I see one invocation
> from wdm_read() and another from service_interrupt_work().
>
> Also, if that would be the case, then spin_unlock_irq() in an USB
> completion handler (which might run in IRQ context with interrupts
> disabled) would be wrong.

Yes, you are right.
I checked an old kernel version Linux-4.16 and got this report.
The current code looks much different from the code that I checked.
Sorry for my false report, and thanks for your correction.


Best wishes,
Jia-Ju Bai