linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Davide Ciminaghi <ciminaghi@gnudd.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>,
	sameo@linux.intel.com, rubini@gnudd.com,
	giancarlo.asnaghi@st.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/8] sta2x11-mfd : add apb-soc regs driver and factor out common code
Date: Fri, 28 Sep 2012 17:29:59 +0200	[thread overview]
Message-ID: <20120928152959.GM22500@mail.gnudd.com> (raw)
In-Reply-To: <20120927151314.118c86c1@pyramind.ukuu.org.uk>

On Thu, Sep 27, 2012 at 03:13:14PM +0100, Alan Cox wrote:
> > as far as I know, nested locks are fine provided that you always take them in
> > the same order and release them in the opposite order (lock A, lock B,
> > unlock B, unlock A). So my conclusion is that nested spinlocks require
> > potential regmap users of sta2x11 registers to take the sta2x11-mfd spinlock
> > first. The pattern would be (sctl registers for instance):
> 
> The release order does not matter. Taking AB and releasing AB or BA is
> fine. Taking AB and dropping B and retaking B is fine. Taking AB and
> somewhere else taking BA is not. There are performance reasons in some
> cases why taking AB releasing A is best with locks, but thats generally
> with sleepable locks.
>
thanks, I'd never really thought about the release pattern actually.
In this particular case, though, B is inside the regmap code and is taken and
released when a regmap call happens, so I think AB necessarily implies BA.
For instance:

lock(A);
regmap_read(...); /* Lock/unlock B */
unlock(A);
 
Thanks
Davide

  reply	other threads:[~2012-09-28 15:30 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-12 10:22 [PATCH 0/8 RESEND] sta2x11-mfd patches ciminaghi
2012-09-12 10:22 ` [PATCH 1/8] sta2x11-mfd : add apb-soc regs driver and factor out common code ciminaghi
2012-09-25 19:20   ` Mark Brown
2012-09-26 14:56     ` Davide Ciminaghi
2012-09-26 15:04       ` Mark Brown
2012-09-26 16:31         ` Davide Ciminaghi
2012-09-26 16:49           ` Mark Brown
2012-09-27  8:39             ` Davide Ciminaghi
2012-09-27  8:56             ` Davide Ciminaghi
2012-09-27 13:41             ` Davide Ciminaghi
2012-09-27 13:49               ` Mark Brown
2012-09-28  8:43                 ` Davide Ciminaghi
2012-09-28 10:52                   ` Mark Brown
2012-09-27 14:13               ` Alan Cox
2012-09-28 15:29                 ` Davide Ciminaghi [this message]
2012-09-12 10:22 ` [PATCH 2/8] sta2x11-mfd : add sta2x11_mfd_get_regs_data() function ciminaghi
2012-09-12 10:22 ` [PATCH 3/8] sta2x11-mfd : use defines for platform devices' names ciminaghi
2012-09-12 10:22 ` [PATCH 4/8] sta2x11-mfd : only add sta2x11_mfd if it hasn't already been added ciminaghi
2012-09-12 10:22 ` [PATCH 5/8] sta2x11-mfd : platform probe: don't mind about gpio platform data ciminaghi
2012-09-12 10:22 ` [PATCH 6/8] sta2x11-mfd : use one lock per device instead of one lock per mfd ciminaghi
2012-09-12 10:22 ` [PATCH 7/8] sta2x11-mfd : add defines for some sta2x11 sctl registers ciminaghi
2012-09-12 10:22 ` [PATCH 8/8] sta2x11-mfd : add myself to copyright ciminaghi
2012-09-16 21:25 ` [PATCH 0/8 RESEND] sta2x11-mfd patches Alessandro Rubini
  -- strict thread matches above, loose matches on Subject: below --
2012-09-12 10:11 ciminaghi
2012-09-12 10:11 ` [PATCH 1/8] sta2x11-mfd : add apb-soc regs driver and factor out common code ciminaghi

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=20120928152959.GM22500@mail.gnudd.com \
    --to=ciminaghi@gnudd.com \
    --cc=alan@lxorguk.ukuu.org.uk \
    --cc=broonie@opensource.wolfsonmicro.com \
    --cc=giancarlo.asnaghi@st.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rubini@gnudd.com \
    --cc=sameo@linux.intel.com \
    /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).