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Date: Fri, 12 Mar 2010 23:39:25 +0100 From: Florian Mickler <florian@...kler.org> To: Dmitry Torokhov <dmitry.torokhov@...il.com> Cc: "John W. Linville" <linville@...driver.com>, Marcel Holtmann <marcel@...tmann.org>, Henrique de Moraes Holschuh <hmh@....eng.br>, Johannes Berg <johannes@...solutions.net>, linux-wireless@...r.kernel.org, Randy Dunlap <rdunlap@...otime.net>, Alan Jenkins <alan-jenkins@...fmail.co.uk>, linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org Subject: Re: [PATCH 2/2] enhance sysfs rfkill interface On Fri, 12 Mar 2010 13:20:26 -0800 Dmitry Torokhov <dmitry.torokhov@...il.com> wrote: > On Fri, Mar 12, 2010 at 09:57:43PM +0100, Florian Mickler wrote: > > On Fri, 12 Mar 2010 10:22:09 -0800 > > Dmitry Torokhov <dmitry.torokhov@...il.com> wrote: > > > > > On Fri, Mar 12, 2010 at 07:03:08PM +0100, florian@...kler.org wrote: > > > > > > > > +static ssize_t rfkill_hard_show(struct device *dev, > > > > + struct device_attribute *attr, > > > > + char *buf) > > > > +{ > > > > + struct rfkill *rfkill = to_rfkill(dev); > > > > + unsigned long flags; > > > > + u32 state; > > > > + > > > > + spin_lock_irqsave(&rfkill->lock, flags); > > > > + state = rfkill->state; > > > > + spin_unlock_irqrestore(&rfkill->lock, flags); > > > > > > Why exactly is this lock needed? > > > > The rfkill state is updated from multiple contexts... Am I overlooking > > smth obvious here? > > > > You are not updating but reading... Are you concerned about seeing > a partial write to u32? It does not happen. > Hm.. You shure? On every arch that supports wireless drivers? I've just copied that code from the old sysfs state-file handler. So I assumed that reading partial updated state can happen... Also I just searched a little but did not find anything, cause i didn't know where to look. Who garantees this? Is it a gcc thing? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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