On 2023/10/26 16:46, Arnd Bergmann wrote:
On Thu, Oct 26, 2023, at 09:39, wuqiang.matt wrote:
arch_cmpxchg[64]_local() are not defined for openrisc. So implement
them with generci_cmpxchg[64]_local, advised by Masami Hiramatsu.
Closes:
https://lore.kernel.org/linux-trace-kernel/169824660459.24340.14614817132696360531.stgit@devnote2
Closes:
https://lore.kernel.org/oe-kbuild-all/[email protected]
Signed-off-by: wuqiang.matt <[email protected]>
I think on architectures that have actual atomics, you
generally want to define this to be the same as arch_cmpxchg()
rather than the generic version.
It depends on the relative cost of doing one atomic compared
to an irq-disable/enable pair, but everyone else went with
the former if they could. The exceptions are armv4/armv5,
sparc32 and parisc, which don't have a generic cmpxchg()
or similar operation.
Sure, better native than the generic. I'll try to collect more
insights before next move.
You could do the thing that sparc64 and xtensa do, which
use the native cmpxchg for supported word sizes but the
generic version for 1- and 2-byte swaps, but that has its
own set of problems if you end up doing operations on both
the entire word and a sub-unit of the same thing.
Thank you for pointing out this. I'll do some research on these
implementations.
Arnd
Regards,
wuqiang
