Messages in this thread | | | From | Rusty Russell <> | Subject | Re: cpumask: fix compat getaffinity | Date | Tue, 18 May 2010 10:27:45 +0930 |
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On Mon, 17 May 2010 03:34:44 pm KOSAKI Motohiro wrote: > > On Wed, 12 May 2010 06:00:45 pm Milton Miller wrote: > > > > > > At least for parsing, we need to allocate and parse NR_CPUS until > > > all places like arch/powerpc/platforms/pseries/xics.c that compare a > > > user-supplied mask to CPUMASK_ALL are eliminated. > > > > Good point. Anton will want to fix those anyway for CONFIG_CPUMASK_OFFSTACK, > > too, but that's the reason the parsing uses nr_cpumask_bits. > > > > > > Would it make sense to use my initial patch for -stable, which reverts > > > > the ABI back to before the change that caused the problem, but apply > > > > the correct fix (changing the ABI throughout) for future releases? > > > > > > This would definitly be the conservative fix. > > > > Instead of changing back to NR_CPUS which will break libnuma for > > CPUMASK_OFFSTACK, how about changing it to nr_cpumask_bits and having an > > explicit comment above it: > > Yes and No. > > 1) sched_getaffinity syscall is used from glibc and libnuma. > 2) glibc doesn't use the return value almostly. glibc emulate it as NR_CPUS=1024. > 3) Now, both sched_getaffinity() and compat_sys_sched_getaffinity() have nr_cpu_ids thing. > 4) But only compat_sys_sched_getaffinity() hit libnuma problem. > > I think It mean compat_sys_sched_getaffinity() should behave as sched_getaffinity(). > IOW, libnuma assume compat_sys_sched_getaffinity() return len args or NR_CPUS. > then, following patch do it. I confirmed the patch works with or without CPUMASK_OFFSTACK. > > So, My proposal is > 1) merge both mine and yours to linus tree > 2) but backport only mine
I think we should just take yours; it seems sufficient.
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
We're going to break at > 4096 cpus whatever we do; I argued with Ingo about it when the affinity syscalls were added but noone thought we'd hit it so soon.
Thanks, Rusty.
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