From: Arnd Bergmann > Sent: 20 December 2023 08:37 > > On Tue, Dec 19, 2023, at 22:03, Sam Ravnborg via B4 Relay wrote: > > TODO before this can be applied: > > - Ack from davem - as he is the principal sparc maintainer > > - Tested-by: preferably on a target or QEMU (see above) > > I expect bugs as there are some involved changes! > > > > Ideas for the future > > - Apply the most relevant downstream Gaisler patches > > - The ones introducing CAS should have preference as we then > > can drop the cmpxchg emulation > > One note about the CAS -- as far as I can tell, the absence > of the futex() syscall on sparc32 kernels means that no glibc > from the past decade can work correctly as it now requires futex > for its internal locking, though it does work on sparc64 kernels > in compat32 mode as well as the LEON3 kernel that adds futex > support. Does the glibc mutex 'fast path' also require a CAS instruction? Presumably having CAS also removes the 'really horrid (tm)' code required to make all the bitmap operations atomic? Seems a shame to lose old sparc32 support when (I think) the sun3 in my cupboard would still work - if only it had a working psu. (The 110/220V switch wasn't connected and the FET wasn't rated for 450V. UK mains can be 240+10% if you are near a substation.) David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
