From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Xenomai <xenomai@xenomai.org>
Subject: Re: [Xenomai] Issue with CONFIG_PREEMPT_VOLUNTARY
Date: Mon, 12 Oct 2015 10:10:28 +0200 [thread overview]
Message-ID: <20151012081028.GA23413@hermes.click-hack.org> (raw)
In-Reply-To: <561B6002.3010409@siemens.com>
On Mon, Oct 12, 2015 at 09:23:46AM +0200, Jan Kiszka wrote:
> On 2015-10-11 15:05, Gilles Chanteperdrix wrote:
> > Hi,
> >
> > It seems commit fdb5d54d04b8c3b6b6a6ad7ac2b6248cf0b415e0 in the
> > I-pipe kernels cause a warning when CONFIG_PREEMPT_VOLUNTARY and
> > CONFIG_IPIPE_DEBUG_INTERNAL are enabled. The culprit is the call to
> > __ipipe_root_p.
>
> Compiler warning? Runtime warning? Which architecture? I assume that
> ftrace is on then, right?
Yes. Because preempt_disable()/preempt_enable*() is a nop without
CONFIG_PREEMPT_COUNT, __ipipe_root_p ends up being called without
any protection, and __ipipe_check_percpu_access() emits the warning.
>
> >
> > The following patch avoids this warning:
>
> How?
It disables the test for preemption (the call to preempt_count()) in
__ipipe_check_percpu_access() if CONFIG_PREEMPT_COUNT is disabled,
because if it is disabled, you can not be preempted anywhere, so
calling __ipipe_root_p without protection is valid. Or maybe not?
--
Gilles.
https://click-hack.org
next prev parent reply other threads:[~2015-10-12 8:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-11 13:05 [Xenomai] Issue with CONFIG_PREEMPT_VOLUNTARY Gilles Chanteperdrix
2015-10-12 7:23 ` Jan Kiszka
2015-10-12 8:10 ` Gilles Chanteperdrix [this message]
2015-10-12 8:37 ` Jan Kiszka
2015-10-12 8:48 ` Gilles Chanteperdrix
2015-10-12 8:58 ` Jan Kiszka
2015-10-12 17:40 ` [Xenomai] [PATCH 1/2] ipipe: simplify __ipipe_check_perccpu_access() Gilles Chanteperdrix
2015-10-12 17:40 ` [Xenomai] [PATCH 2/2] ipipe: fix __ipipe_check_percpu_access() Gilles Chanteperdrix
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