From: Robert Jarzmik <robert.jarzmik@free.fr>
To: Felipe Balbi <balbi@kernel.org>
Cc: Jia-Ju Bai <baijiaju1990@gmail.com>,
gregkh@linuxfoundation.org, nicolas.ferre@microchip.com,
keescook@chromium.org, allen.lkml@gmail.com,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] usb: gadget: r8a66597: Fix two possible sleep-in-atomic-context bugs in init_controller()
Date: Fri, 29 Jun 2018 15:21:19 +0200 [thread overview]
Message-ID: <876021lods.fsf@belgarion.home> (raw)
In-Reply-To: <87bmbtetdk.fsf@linux.intel.com> (Felipe Balbi's message of "Fri, 29 Jun 2018 14:15:19 +0300")
Felipe Balbi <balbi@kernel.org> writes:
> Hi,
>
> Robert Jarzmik <robert.jarzmik@free.fr> writes:
>>>> And as bonus question, why is it better to have mdelay() calls in the driver ?
>>>
>>> As a bugfix, it's the smallest fix possible, right? Ideally, we wouldn't
>>> need either of them. Perhaps there's a bit which can be polled instead?
>> Ideally yes. Do you remember if a "threaded interrupt" might use msleep() ? I
>> seem to remember that they can, so won't that be another alternative ?
>
> yeah, unless, of course, you have a spinlock held. ;-)
Ah yes, unless that :)
I would have proposed to call the disconnect out of the spinlock path, but
looking at the r8a66592_usb_disconnect(), with its spinlock flip-flop, I loose
heart ...
And even if I still think no mdelay() should be used, because of the kernel
stall (and global uniprocessor stall), I won't argue anymore. After all, if you
let in the mdelay(), perhaps the maintainers will agree to review their
architecture and drop the locks or sleeps in interrupt context in a follow-up
patch, who knows ...
Cheers.
--
Robert
prev parent reply other threads:[~2018-06-29 13:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-20 3:54 [PATCH 1/2] usb: gadget: r8a66597: Fix two possible sleep-in-atomic-context bugs in init_controller() Jia-Ju Bai
2018-06-21 9:06 ` Robert Jarzmik
2018-06-29 6:35 ` Felipe Balbi
2018-06-29 6:48 ` Robert Jarzmik
2018-06-29 10:25 ` Felipe Balbi
2018-06-29 11:04 ` Robert Jarzmik
2018-06-29 11:15 ` Felipe Balbi
2018-06-29 13:21 ` Robert Jarzmik [this message]
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