From: Peter Zijlstra <peterz@infradead.org>
To: Peter Rosin <peda@axentia.se>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Wolfram Sang <wsa@the-dreams.de>,
Linus Walleij <linus.walleij@linaro.org>,
Alexandre Courbot <gnurou@gmail.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Vignesh R <vigneshr@ti.com>, Yong Li <yong.b.li@intel.com>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Ingo Molnar <mingo@redhat.com>,
linux-i2c <linux-i2c@vger.kernel.org>,
linux-gpio <linux-gpio@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 0/4] gpio: fix an incorrect lockdep warning
Date: Mon, 19 Sep 2016 11:03:58 +0200 [thread overview]
Message-ID: <20160919090358.GU5016@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <88940f9a-79bf-6c88-8e1d-f76f32dda04a@axentia.se>
On Mon, Sep 19, 2016 at 10:48:44AM +0200, Peter Rosin wrote:
> On 2016-09-19 10:14, Peter Zijlstra wrote:
> > On Mon, Sep 19, 2016 at 10:01:49AM +0200, Peter Rosin wrote:
> >> Or, do what the i2c-mux code is doing and use an rt_mutex instead
> >> of an ordinary mutex. That way you are very sure to not get any
> >> lockdep splat ... at all. Ok, sorry, that was not a serious
> >> suggestion, but it would be a tad bit simpler to implement...
> >
> > So I find it weird that people use rt_mutex as a locking primitive,
> > since its only that one lock that then does PI and all the other locks
> > that are related still create inversions.
>
> So, someone took the bait :-)
>
> Yes, I too find it weird, and would like to get rid of it. It's just
> odd. It's been some years since the start though, waaay before me
> entering kernel space.
>
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=194684e596af4b
>
>
> But it's hard to argue with the numbers given in the discussion:
>
> http://linux-i2c.vger.kernel.narkive.com/nokldJcc/patch-1-1-i2c-prevent-priority-inversion-on-top-of-bus-lock
>
> Has anything happened to the regular mutex implementation that might
> have changed the picture? *crosses fingers*
Use the -RT kernel and all locks will end up as rt_mutex. Avoiding
inversion on one specific lock, while there are then a gazillion other
than can equally create inversion doesn't make sense to me.
next prev parent reply other threads:[~2016-09-19 9:03 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-16 16:02 [PATCH v2 0/4] gpio: fix an incorrect lockdep warning Bartosz Golaszewski
2016-09-16 16:02 ` [PATCH v2 1/4] i2c: export i2c_adapter_depth() Bartosz Golaszewski
2016-09-16 16:02 ` [PATCH v2 2/4] lockdep: make MAX_LOCKDEP_SUBCLASSES unconditionally visible Bartosz Golaszewski
2016-09-16 16:02 ` [PATCH v2 3/4] i2c: add a warning to i2c_adapter_depth() Bartosz Golaszewski
2016-09-16 16:02 ` [PATCH v2 4/4] gpio: pca953x: fix an incorrect lockdep warning Bartosz Golaszewski
2016-09-21 5:45 ` Wolfram Sang
2016-09-23 8:10 ` Linus Walleij
2016-09-24 8:55 ` Wolfram Sang
2016-09-24 9:15 ` Wolfram Sang
2016-09-24 14:26 ` Geert Uytterhoeven
2016-09-16 17:26 ` [PATCH v2 0/4] gpio: " Wolfram Sang
2016-09-16 17:45 ` Peter Rosin
2016-09-16 17:58 ` Wolfram Sang
2016-09-18 8:52 ` Peter Rosin
2016-09-18 19:43 ` Bartosz Golaszewski
2016-09-18 19:45 ` Bartosz Golaszewski
2016-09-19 8:01 ` Peter Rosin
2016-09-19 8:14 ` Peter Zijlstra
2016-09-19 8:48 ` Peter Rosin
2016-09-19 9:03 ` Peter Zijlstra [this message]
2016-09-20 8:48 ` Peter Rosin
2016-09-20 10:07 ` Bartosz Golaszewski
2016-09-20 10:28 ` Peter Zijlstra
2016-09-20 10:48 ` Peter Rosin
2016-09-20 11:30 ` Geert Uytterhoeven
2016-09-20 12:32 ` Bartosz Golaszewski
2016-09-20 15:33 ` Thomas Gleixner
2016-09-21 9:47 ` Peter Rosin
2016-09-17 1:19 ` Peter Zijlstra
2016-09-17 10:18 ` Wolfram Sang
2016-09-17 18:59 ` Bartosz Golaszewski
2016-09-24 8:56 ` Wolfram Sang
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