Messages in this thread | | | Date | Wed, 7 Jan 2009 13:24:24 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning |
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On Wed, 7 Jan 2009, Matthew Wilcox wrote: > > I appreciate this is sample code, but using __get_user() on > non-userspace pointers messes up architectures which have separate > user/kernel spaces (eg the old 4G/4G split for x86-32). Do we have an > appropriate function for kernel space pointers? Is this a good reason > to add one?
Yes, you're right.
We could do the whole "oldfs = get_fs(); set_fs(KERNEL_DS); .. set_fs(oldfs);" crud, but it would probably be better to just add an architected accessor. Especially since it's going to generally just be a
#define get_kernel_careful(val,p) __get_user(val,p)
for most architectures.
We've needed that before (and yes, we've simply mis-used __get_user() on x86 before rather than add it).
Linus
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