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From: Dave Airlie <airlied@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: DRI mailing list <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 2/2] drm: i810/i830: kill BKL, mark as BROKEN_ON_SMP
Date: Thu, 30 Sep 2010 08:15:41 +1000	[thread overview]
Message-ID: <1285798541.15213.125.camel@clockmaker-el6> (raw)
In-Reply-To: <1285775279-31123-3-git-send-email-arnd@arndb.de>

On Wed, 2010-09-29 at 17:47 +0200, Arnd Bergmann wrote:
> The i810 and i830 drivers are the only hardware drivers that
> still use the BKL without anyone volunteering to fix them.

The problem is the userspace interface is badly designed and ABI, so
fixing these without the hw is messy, we know people have the hardware
because it breaks they still give out, we don't know anyone who cares
enough to fix it at this point in time.

> 
> The hardware is rather old and typically used on non-SMP
> systems. Mark them as BROKEN_ON_SMP and remove the BKL
> now so that people can still use the driver once the BKL
> is entirely gone.

You cannot get an SMP system with i810 or i830 support hardware in it,
however no distro ships UP kernels anymore they all ship SMP kernels
that hotplug/patch the second CPU. So the thing is although technically
these drivers are broken on SMP, they won't ever get run in SMP mode on
a combined UP/SMP kernel, and I'm not really sure BROKEN_ON_SMP takes
care of this.

I'm nearly sure the mmap_sem covers the problem anyways, and I should
try and dig out the i815 box I do have access to. Again though I've no
way of knowing we've not broken anything just by booting I assume. If we
introduce a race we would need real testing to find it.

Dave.

  reply	other threads:[~2010-09-29 22:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-29 15:47 [PATCH 0/2] BKL in i810 and i830 drivers Arnd Bergmann
2010-09-29 15:47 ` [PATCH 1/2] drm: i810/i830: fix locked ioctl variant Arnd Bergmann
2010-09-29 15:47 ` [PATCH 2/2] drm: i810/i830: kill BKL, mark as BROKEN_ON_SMP Arnd Bergmann
2010-09-29 22:15   ` Dave Airlie [this message]
2010-09-29 22:48     ` Dave Airlie

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