Re: FP state in threaded coredumps

[Roland McGrath]

> I was adding threaded coredump support to ppc64 and noticed that the
> ELF_CORE_SYNC hook was never called. It looks like we need something
> like this on archs that do lazy FP save/restore to ensure the FP state
> for threads running on other cpus is up to date.

All the threads already synchronize with coredump_wait in __exit_mm.  A
thread reaching that point already has control of the CPU that might be
holding its FPU state.  It seems to me it would be simplest and most
efficient to just do any necessary copy-in there, before
`complete(mm->core_startup_done)'.

Thanks,
Roland