On 02/29/2016 09:24 AM, David Hildenbrand wrote:
>> On 02/27/2016 03:28 PM, John Paul Adrian Glaubitz wrote:
>>> Hi Hans!
>>>
>>> On 02/27/2016 03:20 PM, Geert Uytterhoeven wrote:
>>>>> I noticed that 4.1 was ok and v4.2 wasn't, so I did a git bisect and
>>>>> ended up with
>>>>> commit 8222dbe21e79338de92d5e1956cd1e3994cc9f93 (sched/preempt, mm/fault:
>>>>> Decouple
>>>>> preemption from the page fault logic) as the culprit.
>>>
>>> If you like, please report this the kernel bug tracker and set
>>> "Hardware" to "SuperH". This way we are able to keep track of
>>> the issue.
>>>
>>> I think Yoshinori Sato and Rich Felker will have a look at this.
>>>
>>> Adrian
>>>
>>
>> Done: https://bugzilla.kernel.org/show_bug.cgi?id=113321
>>
>> Regards,
>>
>> Hans
>>
>
> Looks like the code then requires to not be allowed to sleep/preempt in these
> sections (just like kmap_atomic, or kmap_coherent on mips).
>
> So the fix should be simple as (untested):
That fixes it for me:
Tested-by: Hans Verkuil <hans.verk...@cisco.com>
BTW, your patch is garbled and I had to manually make the change (not a big
deal for a simple change like this).
Thanks!
Hans
>
> From d29f0d0cb670175c688cdd181c7a693d28b27a33 Mon Sep 17 00:00:00 2001
>
> From: David Hildenbrand <d...@linux.vnet.ibm.com>
>
> Date: Mon, 29 Feb 2016 09:19:24 +0100
>
> Subject: [PATCH] sched/preempt, sh: kmap_coherent relies on disabled
>
> preemption
>
>
>
> kmap_coherent needs disabled preemption to not schedule in the critical
>
> section, just like kmap_coherent on mips and kmap_atomic in general.
>
>
>
> Fixes: 8222dbe21e79 "sched/preempt, mm/fault: Decouple preemption from the
> page fault logic"
> Reported-by: Hans Verkuil <hverk...@xs4all.nl>
>
> Signed-off-by: David Hildenbrand <d...@linux.vnet.ibm.com>
>
> ---
>
> arch/sh/mm/kmap.c | 2 ++
>
> 1 file changed, 2 insertions(+)
>
>
>
> diff --git a/arch/sh/mm/kmap.c b/arch/sh/mm/kmap.c
>
> index ec29e14..bf25d7c 100644
>
> --- a/arch/sh/mm/kmap.c
>
> +++ b/arch/sh/mm/kmap.c
>
> @@ -36,6 +36,7 @@ void *kmap_coherent(struct page *page, unsigned long addr)
>
>
>
> BUG_ON(!test_bit(PG_dcache_clean, &page->flags));
>
>
>
> + preempt_disable();
>
> pagefault_disable();
>
>
>
> idx = FIX_CMAP_END -
>
> @@ -64,4 +65,5 @@ void kunmap_coherent(void *kvaddr)
>
> }
>
>
>
> pagefault_enable();
>
> + preempt_enable();
>
> }
>
> --
>
> 2.3.9
>
>
>
> David
>
