From: Lars-Peter Clausen <lars@metafoo.de>
To: Greg KH <greg@kroah.com>
Cc: Linux MIPS Mailing List <linux-mips@linux-mips.org>,
David Daney <ddaney.cavm@gmail.com>,
Linux-sh list <linux-sh@vger.kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
platform-driver-x86@vger.kernel.org,
"linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
driverdevel <devel@driverdev.osuosl.org>,
Alexandre Courbot <gnurou@gmail.com>,
patches@opensource.wolfsonmicro.com,
linux-samsungsoc@vger.kernel.org,
Geert Uytterhoeven <geert@linux-m68k.org>,
"linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
abdoulaye berthe <berthe.ab@gmail.com>,
spear-devel@list.st.com,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
m@bues.ch,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
linux-wireless <linux-wireless@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel
Subject: Re: [PATCH 2/2] gpio: gpiolib: set gpiochip_remove retval to void
Date: Sat, 31 May 2014 09:35:39 +0200 [thread overview]
Message-ID: <5389864B.4000107@metafoo.de> (raw)
In-Reply-To: <20140530232922.GD25854@kroah.com>
On 05/31/2014 01:29 AM, Greg KH wrote:
> On Fri, May 30, 2014 at 08:16:59PM +0200, Lars-Peter Clausen wrote:
>> On 05/30/2014 07:33 PM, David Daney wrote:
>>> On 05/30/2014 04:39 AM, Geert Uytterhoeven wrote:
>>>> On Fri, May 30, 2014 at 1:30 PM, abdoulaye berthe <berthe.ab@gmail.com>
>>>> wrote:
>>>>> --- a/drivers/gpio/gpiolib.c
>>>>> +++ b/drivers/gpio/gpiolib.c
>>>>> @@ -1263,10 +1263,9 @@ static void gpiochip_irqchip_remove(struct
>>>>> gpio_chip *gpiochip);
>>>>> *
>>>>> * A gpio_chip with any GPIOs still requested may not be removed.
>>>>> */
>>>>> -int gpiochip_remove(struct gpio_chip *chip)
>>>>> +void gpiochip_remove(struct gpio_chip *chip)
>>>>> {
>>>>> unsigned long flags;
>>>>> - int status = 0;
>>>>> unsigned id;
>>>>>
>>>>> acpi_gpiochip_remove(chip);
>>>>> @@ -1278,24 +1277,15 @@ int gpiochip_remove(struct gpio_chip *chip)
>>>>> of_gpiochip_remove(chip);
>>>>>
>>>>> for (id = 0; id < chip->ngpio; id++) {
>>>>> - if (test_bit(FLAG_REQUESTED, &chip->desc[id].flags)) {
>>>>> - status = -EBUSY;
>>>>> - break;
>>>>> - }
>>>>> - }
>>>>> - if (status == 0) {
>>>>> - for (id = 0; id < chip->ngpio; id++)
>>>>> - chip->desc[id].chip = NULL;
>>>>> -
>>>>> - list_del(&chip->list);
>>>>> + if (test_bit(FLAG_REQUESTED, &chip->desc[id].flags))
>>>>> + panic("gpio: removing gpiochip with gpios still
>>>>> requested\n");
>>>>
>>>> panic?
>>>
>>> NACK to the patch for this reason. The strongest thing you should do here
>>> is WARN.
>>>
>>> That said, I am not sure why we need this whole patch set in the first place.
>>
>> Well, what currently happens when you remove a device that is a provider of
>> a gpio_chip which is still in use, is that the kernel crashes. Probably with
>> a rather cryptic error message. So this patch doesn't really change the
>> behavior, but makes it more explicit what is actually wrong. And even if you
>> replace the panic() by a WARN() it will again just crash slightly later.
>>
>> This is a design flaw in the GPIO subsystem that needs to be fixed.
>
> Then fix the GPIO code properly, don't add a new panic() to the kernel.
Until somebody comes up with a patch that fixes this for good I think that
patch is still an improvement over the current situation. Rather than
keeping the kernel running in a inconsistent state, which might cause all
kinds of undefined behavior and which will lead to a crash eventually, we
might as well just crash the kernel at the cause of the inconsistent state.
This will make it obvious why it crashed (compared to a random stacktrace)
and will also prevent the kernel from running in a undefined state.
- Lars
next prev parent reply other threads:[~2014-05-31 7:35 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-29 21:54 [PATCH] gpio: removes all usage of gpiochip_remove retval abdoulaye berthe
2014-05-29 22:14 ` David Daney
2014-05-29 23:16 ` abdoulaye berthe
2014-05-29 23:40 ` Stephen Rothwell
2014-05-30 11:30 ` [PATCH 1/2] " abdoulaye berthe
2014-05-30 11:30 ` [PATCH 2/2] gpio: gpiolib: set gpiochip_remove retval to void abdoulaye berthe
2014-05-30 11:39 ` Geert Uytterhoeven
2014-05-30 15:48 ` Ralf Baechle
2014-05-30 17:33 ` David Daney
2014-05-30 18:16 ` Lars-Peter Clausen
2014-05-30 23:29 ` Greg KH
2014-05-31 7:35 ` Lars-Peter Clausen [this message]
2014-05-31 12:19 ` Dan Carpenter
2014-06-08 23:18 ` Ben Dooks
2014-06-09 11:29 ` Lars-Peter Clausen
2014-06-09 13:15 ` Andrzej Hajda
2014-06-09 13:43 ` David Laight
2014-06-10 6:57 ` Andrzej Hajda
2014-05-29 23:25 ` [PATCH] gpio: removes all usage of gpiochip_remove retval Greg KH
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