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Groups > linux.kernel > #1165537
| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: why do we need vmalloc_sync_all? |
| Date | 2015-06-15 22:30 +0200 |
| Message-ID | <pBJb5-5IV-29@gated-at.bofh.it> (permalink) |
| References | (1 earlier) <pAYOS-4Iu-1@gated-at.bofh.it> <pBb9n-6cY-3@gated-at.bofh.it> <pBmo9-6xN-3@gated-at.bofh.it> <pBsDf-6ZX-1@gated-at.bofh.it> <pBsMW-7b9-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
* Andy Lutomirski <luto@amacapital.net> wrote: > On Sun, Jun 14, 2015 at 7:47 PM, Andi Kleen <andi@firstfloor.org> wrote: > > Oleg Nesterov <oleg@redhat.com> writes: > >> > >> But again, the kernel no longer does this? do_page_fault() does > >> vmalloc_fault() without notify_die(). If it fails, I do not see how/why a > >> modular DIE_OOPS handler could try to resolve this problem and trigger > >> another fault. > > > > The same problem can happen from NMI handlers or machine check handlers. It's > > not necessarily tied to page faults only. > > AIUI, the point of the one and only vmalloc_sync_all call is to prevent > infinitely recursive faults when we call a notify_die callback. The only thing > that it could realistically protect is module text or static non-per-cpu module > data, since that's the only thing that's reliably already in the init pgd. I'm > with Oleg: I don't see how that can happen, since do_page_fault fixes up vmalloc > faults before it calls notify_die. Yes, but what I meant is that it can happen if due to an unrelated kernel bug and unlucky timing we have installed this new handler just when that other unrelated kernel bug triggers: say a #GPF crash in kernel code. In any case it should all be mooted with the removal of lazy PGD instantiation. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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Re: why do we need vmalloc_sync_all? Oleg Nesterov <oleg@redhat.com> - 2015-06-14 22:10 +0200
Re: why do we need vmalloc_sync_all? Ingo Molnar <mingo@kernel.org> - 2015-06-15 22:30 +0200
Re: why do we need vmalloc_sync_all? Andy Lutomirski <luto@amacapital.net> - 2015-06-15 22:50 +0200
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