Messages in this thread | | | Date | Thu, 27 Nov 2014 09:03:01 +0100 | From | David Hildenbrand <> | Subject | Re: [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic |
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> Code like > spin_lock(&lock); > if (copy_to_user(...)) > rc = ... > spin_unlock(&lock); > really *should* generate warnings like it did before. > > And *only* code like > spin_lock(&lock);
Is only code like this valid or also with the spin_lock() dropped? (e.g. the access in patch1 if I remember correctly)
So should page_fault_disable() increment the pagefault counter and the preempt counter or only the first one?
> page_fault_disable(); > if (copy_to_user(...)) > rc = ... > page_fault_enable(); > spin_unlock(&lock); > should not generate warnings, since the author hopefully knew what he did. > > We could achieve that by e.g. adding a couple of pagefault disabled bits > within current_thread_info()->preempt_count, which would allow > pagefault_disable() and pagefault_enable() to modify a different part of > preempt_count than it does now, so there is a way to tell if pagefaults have > been explicitly disabled or are just a side effect of preemption being > disabled. > This would allow might_fault() to restore its old sane behaviour for the > !page_fault_disabled() case.
So we would have pagefault code rely on:
in_disabled_pagefault() ( pagefault_disabled() ... whatever ) instead of in_atomic().
I agree with this approach, as this is basically what I suggested in one of my previous mails.
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