From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: Re: [ACPI] inappropriate use of in_atomic() Date: Sat, 12 Mar 2005 11:22:54 +1100 Message-ID: <1110586974.5752.141.camel@gaston> References: <20050310204006.48286d17.akpm@osdl.org> <20050311091142.GB22415@fi.muni.cz> <20050311014601.166ae43d.akpm@osdl.org> <1110543974.5809.98.camel@gaston> <20050311161335.1e601da1.akpm@osdl.org> Reply-To: linux-fbdev-devel@lists.sourceforge.net Mime-Version: 1.0 Content-Transfer-Encoding: 7bit In-Reply-To: <20050311161335.1e601da1.akpm@osdl.org> Sender: linux-fbdev-devel-admin@lists.sourceforge.net Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" To: Andrew Morton Cc: Linux Fbdev development list , kas@fi.muni.cz, Paul Mackerras , jt@bougret.hpl.hp.com, javier@tudela.mad.ttd.net, acpi-devel@lists.sourceforge.net, linux1394-devel@lists.sourceforge.net, roland@topspin.com, Linux Kernel list On Fri, 2005-03-11 at 16:13 -0800, Andrew Morton wrote: > (where'd my cc go?) > > Benjamin Herrenschmidt wrote: > > > > On Fri, 2005-03-11 at 01:46 -0800, Andrew Morton wrote: > > > Jan Kasprzak wrote: > > > > > > > > This may be the cause of > > > > > > > > http://bugme.osdl.org/show_bug.cgi?id=4150 > > > > > > Looks that way, yes. > > > > Note that it would be interesting to fix that (I mean the reliability of > > is_atomic() or an alternative). I agree it's quite bad to rely on that > > in practice, but there are a few corner cases where it's useful (like > > oops handling in fbdev's etc...) > > > > That would require that we increment current->something on every > spin/read/write_lock and decrement it in unlock, even with !CONFIG_PREEMPT. > > iirc, Anton added an option to do that to the ppc64 build, decoupled from > CONFIG_PREEMPT (which ppc64 doesn't support). ppc64 _does_ support PREEMPT nowadays :) > But it's an appreciable amount of overhead. -- Benjamin Herrenschmidt ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click