From: Daniel Drake <dsd@laptop.org>
To: Vitaly Wool <vitalywool@gmail.com>
Cc: Ulf Hansson <ulf.hansson@stericsson.com>,
linux-mmc@vger.kernel.org, Chris Ball <cjb@laptop.org>,
Per Forlin <per.forlin@stericsson.com>,
Johan Rudholm <johan.rudholm@stericsson.com>,
Lee Jones <lee.jones@linaro.org>
Subject: Re: [PATCH] mmc: core: Do not pre-claim host in suspend
Date: Thu, 19 Apr 2012 09:48:36 -0600 [thread overview]
Message-ID: <CAMLZHHQVrog2srUhOjH5T3bQN4DjjP04x0ko3Bv9CXYyo_8i9Q@mail.gmail.com> (raw)
In-Reply-To: <CAMJBoFNO7aKge9BqawRJdr=k_HxOOaeoPaif1sed_vN7kSF35g@mail.gmail.com>
On Thu, Apr 19, 2012 at 4:02 AM, Vitaly Wool <vitalywool@gmail.com> wrote:
> I think it looks like a hack. Can you provide a better description of
> where this deadlock actually happens?
>
> If libertas_sdio claims host as a part of its suspend operation from a
> context different from the suspend context, isn't it libertas_sdio
> that has to be fixed?
libertas_sdio performs work in a workqueue during the suspend routine.
It doesn't take long, but it is essential.
Technically it would be possible to do the same work from the suspend
thread without changing context. However, implementation-wise this is
quite difficult. We cannot simply blast commands off to the card
directly, we have to obey various rules and keep things in sync. This
is done with an abstraction layer in the driver which is also shared
with equivalent devices that connect over USB, SPI, etc. Sometimes we
send commands from atomic context, or asynchronously, so thats why we
do things in a workqueue.
Breaking this abstraction for the suspend corner-case would be a pain,
and I don't agree with the strange requirement that SDIO drivers can't
communicate from other contexts in the suspend routine. My thoughts
are here: http://article.gmane.org/gmane.linux.kernel.mmc/13899
Ulf, you have understood the problem correctly and your patch solves
the issue. Thanks for the fast response.
Daniel
next prev parent reply other threads:[~2012-04-19 15:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-19 9:55 [PATCH] mmc: core: Do not pre-claim host in suspend Ulf Hansson
2012-04-19 10:02 ` Vitaly Wool
2012-04-19 15:48 ` Daniel Drake [this message]
2012-04-20 8:55 ` Ulf Hansson
2012-04-20 13:39 ` Daniel Drake
2012-04-20 13:41 ` Chris Ball
2012-04-20 17:17 ` Sujit Reddy Thumma
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