On Sat, May 26, 2007 at 04:00:56PM -0700, David Miller wrote: > From: Dave Airlie <airlied@xxxxxxxx> > Date: Sat, 26 May 2007 21:32:10 +0100 (IST) > > > the DRM can use cmpxchg in userspace, to implement DRM_CAS, have a look in > > drm git libdrm/xf86drm.h we appear to have a sparc implementation, this > > gives us fast userspace locking, however if an arch doesn't implement > > DRM_CAS we fallback to the heavyweight in-kernel lock, > > That instruction only works on sparc64 cpus, which includes > 32-bit apps running a system with sparc64 cpus. > > That's why I hard-code the opcode in that asm statement of > the DRM sources. > I don't see what the problem is? If we can't do it in userspace, we fall back to a heavyweight ioctl lock. This sounds sensible to me. On parisc we implement userspace CAS with a lightweight syscall on our gateway page, likely something like this could be implemented if someone cared on sparc32 as well using a VDSO. Cheers, Kyle - 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
