From: Jiri Gaisler <jiri@xxxxxxxxxxx> Date: Wed, 22 Dec 2010 10:51:05 +0100 > > > Alex Buell wrote: >> On Tue, 2010-12-21 at 19:54 -0800, David Miller wrote: >>>> We are thinking of switching the LEON port to use CASA (compare and >>> swap), just like in the sparc64 port. Most newer leon3/4 processors >>> implement CASA, even if the instruction belongs to sparc V9 and not >>> V8. Would a patch like that be accepted (for the LEON port only)? This >>> will not fix the SMP for general sparc32 (which really is broken), but >>> it would fix it for LEON. >>> >>> It should be fine as long as the patches are clean enough. >> >> Rather than specialising it for LEON, why not just test for CASA >> availability and use it if it available? > > The CASA is only necessary for SMP systems, as the current irq15 > solution will NOT work on sparc32-SMP. So falling back on irq15 > when CASA is not present is not really an option, as it will lead > to a deadlock sooner or later ... Well actually, you can't just implement CAS and not fix the irq15 issue. Spinlocks and other code that does local_disable_irq() expects that smp_call_function() would be blocks by such disables and they won't and you will crash if you don't fix this. So no matter what someone has to fix the irq15 NMI issue. -- 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
