Messages in this thread |  | | Date | Wed, 22 Oct 2014 22:20:27 +0200 | From | Oleg Nesterov <> | Subject | Re: introduce probe_slab_address? |
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On 10/22, David Miller wrote: > > From: Oleg Nesterov <oleg@redhat.com> > Date: Wed, 22 Oct 2014 21:42:28 +0200 > > > Now the question: is this LOAD is safe in case when this (freed) page > > already has another mapping? This is black magic to me, I do not know. > > And Peter has some concerns. > > It is immatieral, because you can read garbage and it's "don't care" > in this context. > > And later if it is used again at this virtual address, it will be > initialized with stores at that virtual address first. > > So no problem.
Great, thanks.
> > And, say, copy_from_user_page() on sparc does > > > > flush_cache_page(); > > memcpy(); > > flush_ptrace_access(); > > In this case, as I tried to explain, it matters because the physical > address is being accessed from two virtual address at the same time > "for the same usage". > > That's what distinguishes this from the SLAB and RCU cases you cite.
Yes, this was my (vague) understanding, but thanks for another explanation anyway.
Oleg.
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