On Sun, May 27, 2007 at 07:49:21PM -0700, David Miller wrote: > From: Martin Habets <errandir_news@xxxxxxxxxxxxxxxxx> > Date: Mon, 28 May 2007 01:07:46 +0100 > > > On Sat, May 26, 2007 at 03:59:21PM -0700, David Miller wrote: > > > Alternatively we can have a KCONFIG variable with reversed > > > logic, like "EMULATED_CMPXCHG" which only the atomically > > > challenged platforms need to set. > > > > Like this idea, but if we're not going to build DRM I see no > > point adding the cmpxchg emulation to sparc32. Maybe "NOARCH_CMPXCHG" > > would be better? > > It is likely that we are going to have generic users of cmpxchg() in > the kernel in the future (I think the -rt patch set has some which are > hard to get rid of) at which point we'd probably put the emulated > cmpxchg() in there anyways. Good to see someone has a crystal ball handy. So a patch like like this to solve the DRM issue? With it DRM can no longer be selected. --- The DRM code depends on an atomic version of cmpxchg(), which is not available on sparc32. Since other platforms besides sparc32 have this issue a KCONFIG option is added for it. Martin Signed-off-by: Martin Habets <errandir_news@xxxxxxxxxxxxxxxxx> Index: 2.6.21_drm/drivers/char/drm/Kconfig =================================================================== --- 2.6.21_drm.orig/drivers/char/drm/Kconfig 2007-05-26 00:18:45.000000000 +0100 +++ 2.6.21_drm/drivers/char/drm/Kconfig 2007-05-28 23:49:12.000000000 +0100 @@ -6,7 +6,7 @@ # config DRM tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)" - depends on (AGP || AGP=n) && PCI + depends on (AGP || AGP=n) && PCI && !EMULATED_CMPXCHG help Kernel-level support for the Direct Rendering Infrastructure (DRI) introduced in XFree86 4.0. If you say Y here, you need to select Index: 2.6.21_drm/arch/sparc/Kconfig =================================================================== --- 2.6.21_drm.orig/arch/sparc/Kconfig 2007-05-23 19:31:01.000000000 +0100 +++ 2.6.21_drm/arch/sparc/Kconfig 2007-05-29 00:03:16.000000000 +0100 @@ -178,6 +178,13 @@ bool default n +config EMULATED_CMPXCHG + bool + default y + help + Sparc32 does not have a CAS instruction like sparc64. cmpxchg() + is emulated, and therefore it is not completely atomic. + config SUN_PM bool default y - To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
