linux-kernel - Re: [PATCH 0/7] convert semaphore to mutex in struct class

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Date:	Tue, 8 Jan 2008 15:05:10 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Greg KH" <gregkh@...e.de>
Cc:	"Stefan Richter" <stefanr@...6.in-berlin.de>,
	James.Bottomley@...senpartnership.com,
	dbrownell@...rs.sourceforge.net, linux-scsi@...r.kernel.org,
	a.zummo@...ertech.it, peterz@...radead.org, cbou@...l.ru,
	linux-kernel@...r.kernel.org,
	"David Brownell" <david-b@...bell.net>, krh@...hat.com,
	stern@...land.harvard.edu, rtc-linux@...glegroups.com,
	spi-devel-general@...ts.sourceforge.net,
	linux1394-devel@...ts.sourceforge.net, dwmw2@...radead.org,
	davem@...emloft.net, jarkao2@...il.com
Subject: Re: [PATCH 0/7] convert semaphore to mutex in struct class

On Jan 8, 2008 1:20 AM, Greg KH <gregkh@...e.de> wrote:
> On Mon, Jan 07, 2008 at 06:13:37PM +0100, Stefan Richter wrote:
> > It's already in the driver core to the most part.  It remains to be seen
> > what is less complicated in the end:  Transparent mutex-protected list
> > accesses provided by driver core (requires the iterator), or all the
> > necessary locking done by the drivers themselves (requires some more
> > lock-taking but perhaps fewer lock instances overall in the drivers, and
> > respective redefinitions and documentation of the driver core API).
>
> I favor changing the driver core api and doing this kind of thing there.
> It keeps the drivers simpler and should hopefully make their lives
> easier.

What about this?

#define class_for_each_dev(pos, head, member) \
        for (mutex_lock(&(container_of(head, struct class, devices))->mutex), po
s = list_entry((head)->next, typeof(*pos), member); \
        prefetch(pos->member.next), &pos->member != (head) ? 1 : (mutex_unlock(&
(container_of(head, struct class, devices))->mutex), 0); \
        pos = list_entry(pos->member.next, typeof(*pos), member))

>
> > Semi off-topic:  What about struct device.sem?  Is there any chance to
> > rip this out of the driver core and let drivers serialize everything?  I
> > suppose not...
>
> See the previous long threads about this very topic, that is what caused
> this class.sem patches :)
>
> thanks,
>
> greg k-h
>
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