Messages in this thread | | | Date | Thu, 2 May 2013 10:52:41 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH RFC] x86: uaccess s/might_sleep/might_fault/ |
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* Michael S. Tsirkin <mst@redhat.com> wrote:
> The only reason uaccess routines might sleep > is if they fault. Make this explicit for > __copy_from_user_nocache, and consistent with > copy_from_user and friends. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > > I've updated all other arches as well - still > build-testing. Any objections to the x86 patch? > > arch/x86/include/asm/uaccess_64.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h > index 142810c..4f7923d 100644 > --- a/arch/x86/include/asm/uaccess_64.h > +++ b/arch/x86/include/asm/uaccess_64.h > @@ -235,7 +235,7 @@ extern long __copy_user_nocache(void *dst, const void __user *src, > static inline int > __copy_from_user_nocache(void *dst, const void __user *src, unsigned size) > { > - might_sleep(); > + might_fault(); > return __copy_user_nocache(dst, src, size, 1);
Looks good to me:
Acked-by: Ingo Molnar <mingo@kernel.org>
... but while reviewing the effects I noticed a bug in might_fault():
#ifdef CONFIG_PROVE_LOCKING void might_fault(void) { /* * Some code (nfs/sunrpc) uses socket ops on kernel memory while * holding the mmap_sem, this is safe because kernel memory doesn't * get paged out, therefore we'll never actually fault, and the * below annotations will generate false positives. */ if (segment_eq(get_fs(), KERNEL_DS)) return;
might_sleep();
the might_sleep() call should come first. With the current code might_fault() schedules differently depending on CONFIG_PROVE_LOCKING, which is an undesired semantical side effect ...
So please fix that too while at it.
Thanks,
Ingo
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