linux-gpio.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Kent Gibson <warthog618@gmail.com>
To: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-gpio <linux-gpio@vger.kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH 08/22] gpiolib: cdev: complete the irq/thread timestamp handshake
Date: Wed, 24 Jun 2020 22:08:06 +0800	[thread overview]
Message-ID: <20200624140806.GA7569@sol> (raw)
In-Reply-To: <CAMpxmJVbiH9mh2c8aAS+GG9a76w9c0Nrrv-VDVhpo+wSyQ2NeQ@mail.gmail.com>

On Wed, Jun 24, 2020 at 04:00:42PM +0200, Bartosz Golaszewski wrote:
> wt., 23 cze 2020 o 06:02 Kent Gibson <warthog618@gmail.com> napisał(a):
> >
> > Reset the timestamp field to 0 after using it in lineevent_irq_thread.
> >
> > The timestamp is set by lineevent_irq_handler and is tested by
> > lineevent_irq_thread to determine if it is called from a nested theaded
> > interrupt.
> > lineevent_irq_thread is assuming that the nested, or otherwise, status
> > of the IRQ is static, i.e. it is either always nested or never nested.
> > This change removes that assumption, resetting the timestamp so it can
> > be re-used to determine the nested state of subsequent interrupts.
> >
> > Signed-off-by: Kent Gibson <warthog618@gmail.com>
> >
> 
> This change makes sense to me but I'm having a hard time processing
> the explanation. If we're requesting the interrupt and allocating the
> lineevent state in the same function - how can we run into a situation
> here the status of the irq would change like what you describe?
> 

I'm not totally sure myself, as my understanding of how interrupts are
shared in the kernel is pretty sketchy, but my concern is that if we
are sharing the irq then whoever we are sharing with may release the irq
and we go from nested to unnested.  Or vice versa.  Not sure if that is
valid, but that was my concern, and it seemed like a minor change to
cover it just in case.

Cheers,
Kent.

  reply	other threads:[~2020-06-24 14:08 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23  4:00 [PATCH 00/22] gpio: cdev: add uAPI V2 Kent Gibson
2020-06-23  4:00 ` [PATCH 01/22] gpiolib: move gpiolib-sysfs function declarations into their own header Kent Gibson
2020-06-24 13:34   ` Bartosz Golaszewski
2020-06-24 13:38     ` Kent Gibson
2020-06-23  4:00 ` [PATCH 02/22] gpiolib: cdev: sort includes Kent Gibson
2020-06-24 13:34   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 03/22] gpiolib: cdev: minor indentation fixes Kent Gibson
2020-06-24 13:35   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 04/22] gpiolib: cdev: refactor gpiohandle_flags_to_desc_flags Kent Gibson
2020-06-24 13:51   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 05/22] gpiolib: cdev: rename 'filep' and 'filp' to 'file' to be consistent with other use Kent Gibson
2020-06-24 13:52   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 06/22] gpiolib: cdev: rename numdescs to num_descs Kent Gibson
2020-06-24 13:53   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 07/22] gpiolib: cdev: remove pointless decrement of i Kent Gibson
2020-06-24 13:53   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 08/22] gpiolib: cdev: complete the irq/thread timestamp handshake Kent Gibson
2020-06-24 14:00   ` Bartosz Golaszewski
2020-06-24 14:08     ` Kent Gibson [this message]
2020-06-25  9:44       ` Bartosz Golaszewski
2020-06-25 10:01         ` Kent Gibson
2020-06-30  9:08           ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 09/22] gpiolib: cdev: rename priv to gcdev Kent Gibson
2020-06-24 14:04   ` Bartosz Golaszewski
2020-06-24 14:19     ` Kent Gibson
2020-06-24 14:20       ` Bartosz Golaszewski
2020-06-24 23:16         ` Kent Gibson
2020-06-25 10:26           ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 10/22] gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH Kent Gibson
2020-06-24 14:05   ` Bartosz Golaszewski
2020-06-24 14:46   ` Andy Shevchenko
2020-06-24 15:57     ` Kent Gibson
2020-06-24 22:58       ` Kent Gibson
2020-06-25  8:44         ` Andy Shevchenko
2020-06-25  9:13           ` Kent Gibson
2020-06-25  9:23             ` Andy Shevchenko
2020-06-25  9:36               ` Kent Gibson
2020-06-23  4:00 ` [PATCH 11/22] gpiolib: cdev: remove recalculation of offset Kent Gibson
2020-06-30  8:56   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 12/22] gpio: uapi: define GPIO_MAX_NAME_SIZE for array sizes Kent Gibson
2020-06-24 14:13   ` Bartosz Golaszewski
2020-06-23  4:00 ` [PATCH 13/22] gpio: uapi: define uAPI V2 Kent Gibson
2020-06-24 14:33   ` Andy Shevchenko
2020-06-24 15:40     ` Kent Gibson
2020-06-26 14:02       ` Kent Gibson
2020-06-24 14:36   ` Bartosz Golaszewski
2020-06-24 23:58     ` Kent Gibson
2020-06-23  4:00 ` [PATCH 14/22] gpiolib: make cdev a build option Kent Gibson
2020-06-29 14:25   ` Bartosz Golaszewski
2020-06-23  4:01 ` [PATCH 15/22] gpiolib: add build option for CDEV V1 ABI Kent Gibson
2020-06-29 14:26   ` Bartosz Golaszewski
2020-06-23  4:01 ` [PATCH 16/22] gpiolib: cdev: add V2 uAPI implementation to parity with V1 Kent Gibson
2020-06-23 17:44   ` Dan Carpenter
2020-06-23 23:23     ` Kent Gibson
2020-06-23  4:01 ` [PATCH 17/22] gpiolib: cdev: report edge detection in lineinfo Kent Gibson
2020-06-23  4:01 ` [PATCH 18/22] gpiolib: cdev: support setting debounce Kent Gibson
2020-06-23  4:01 ` [PATCH 19/22] gpio: uapi: document uAPI V1 as deprecated Kent Gibson
2020-06-23  4:01 ` [PATCH 20/22] tools: gpio: switch tools to V2 uAPI Kent Gibson
2020-06-23  4:01 ` [PATCH 21/22] tools: gpio: add debounce support to gpio-event-mon Kent Gibson
2020-06-23  4:01 ` [PATCH 22/22] tools: gpio: support monitoring multiple lines Kent Gibson
2020-06-30 10:43   ` Bartosz Golaszewski

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200624140806.GA7569@sol \
    --to=warthog618@gmail.com \
    --cc=bgolaszewski@baylibre.com \
    --cc=linus.walleij@linaro.org \
    --cc=linux-gpio@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).