On Wednesday 04 May 2016 08:31 PM, Peter Zijlstra wrote:
> So I'm fairly sure people rely on the fact you cannot have pagefault
> inside a kmap_atomic().
So this translates to: any hardware page faults inside kmap_atomic() can't lead
to
do_page_fault() taking a lock - those can only be ex_table f
On Wed, May 04, 2016 at 08:17:55PM +0100, Russell King - ARM Linux wrote:
> On Wed, May 04, 2016 at 03:47:29PM +0200, Peter Zijlstra wrote:
> > Traditionally kmap_atomic() disables preemption; and the reason is that
> > the returned pointer must stay valid. This had a side effect in that it
> > als
On Wed, May 04, 2016 at 03:47:29PM +0200, Peter Zijlstra wrote:
> Traditionally kmap_atomic() disables preemption; and the reason is that
> the returned pointer must stay valid. This had a side effect in that it
> also disabled pagefaults.
A lowmem page should never change its page_address(), so t
On Wed, May 04, 2016 at 02:16:11PM +, Vineet Gupta wrote:
> > static inline void *kmap_atomic(struct page *page)
> > {
> > preempt_disable();
> > pagefault_disable();
> > if (!PageHighMem(page))
> > return page_address(page);
> >
> > return __kmap_atomic(page);
> > }
On Wednesday 04 May 2016 07:17 PM, Peter Zijlstra wrote:
> On Wed, May 04, 2016 at 04:07:40PM +0530, Vineet Gupta wrote:
>> Is preemption disabling a requirement of kmap_atomic() callers independent of
>> where page is or is it only needed when page is in highmem and can trigger
>> page
>> faults
On Wednesday 04 May 2016 07:23 PM, Thomas Petazzoni wrote:
> Hello,
>
> On Wed, 4 May 2016 15:47:29 +0200, Peter Zijlstra wrote:
>
>> static inline void *kmap_atomic(struct page *page)
>> {
>> preempt_disable();
>> pagefault_disable();
>> if (!PageHighMem(page))
>> retur
Hello,
On Wed, 4 May 2016 15:47:29 +0200, Peter Zijlstra wrote:
> static inline void *kmap_atomic(struct page *page)
> {
> preempt_disable();
> pagefault_disable();
> if (!PageHighMem(page))
> return page_address(page);
>
> return __kmap_atomic(page);
> }
T
On Wed, May 04, 2016 at 04:07:40PM +0530, Vineet Gupta wrote:
> Hi,
>
> I was staring at some recent ARC highmem crashes and see that kmap_atomic()
> disables preemption even when page is in lowmem and call returns right away.
> This seems to be true for other arches as well.
>
> arch/arc/mm/high
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