linux-kernel - Re: [PATCH v2 01/25] mm: Add kfd_process pointer to mm

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Date:	Thu, 17 Jul 2014 17:15:30 +0300
From:	Oded Gabbay <oded.gabbay@....com>
To:	Jerome Glisse <j.glisse@...il.com>
CC:	David Airlie <airlied@...ux.ie>,
	Alex Deucher <alexdeucher@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Bridgman <John.Bridgman@....com>,
	Joerg Roedel <joro@...tes.org>,
	Andrew Lewycky <Andrew.Lewycky@....com>,
	Christian König <deathsimple@...afone.de>,
	Michel Dänzer <michel.daenzer@....com>,
	Ben Goz <Ben.Goz@....com>,
	Alexey Skidanov <Alexey.Skidanov@....com>,
	Evgeny Pinchuk <Evgeny.Pinchuk@....com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Jérôme Glisse <jglisse@...hat.com>,
	<linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v2 01/25] mm: Add kfd_process pointer to mm_struct

On 17/07/14 17:12, Jerome Glisse wrote:
> On Thu, Jul 17, 2014 at 04:57:58PM +0300, Oded Gabbay wrote:
>> Forgot to add mm mailing list. Sorry.
>>
>> This patch enables the amdkfd driver to retrieve the kfd_process
>> object from the process's mm_struct. This is needed because kfd_process
>> lifespan is bound to the process's mm_struct lifespan.
>>
>> When amdkfd is notified about an mm_struct tear-down, it checks if the
>> kfd_process pointer is valid. If so, it releases the kfd_process object
>> and all relevant resources.
>>
>> In v3 of the patchset I will update the binding to match the final discussions
>> on [PATCH 1/8] mmput: use notifier chain to call subsystem exit handler.
>> In the meantime, I'm going to try and see if I can drop the kfd_process
>> in mm_struct and remove the use of the new notification chain in mmput.
>> Instead, I will try to use the mmu release notifier.
>
> So the mmput notifier chain will not happen. I did a patch with call_srcu
> and adding couple more helper to mmu_notifier. I will send that today for
> review.
>
> That being said, adding a device driver specific to mm_struct will most
> likely be a big no. I am myself gonna remove hmm from mm_struct as people
> are reluctant to see such change.
>
> Cheers,
> Jérôme
>
Yes, I followed that email thread and you can see that in the commit message I 
referred to it (saying that in v3 of the patchset I'm also going to use 
mmu_notifier). I will take your patch once you publish it and use it to change 
amdkfd behavior.

	Oded
>
>>
>> Signed-off-by: Oded Gabbay <oded.gabbay@....com>
>> ---
>>   include/linux/mm_types.h | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
>> index 678097c..ff71496 100644
>> --- a/include/linux/mm_types.h
>> +++ b/include/linux/mm_types.h
>> @@ -20,6 +20,10 @@
>>   struct hmm;
>>   #endif
>>   +#if defined(CONFIG_HSA_RADEON) || defined(CONFIG_HSA_RADEON_MODULE)
>> +struct kfd_process;
>> +#endif
>> +
>>   #ifndef AT_VECTOR_SIZE_ARCH
>>   #define AT_VECTOR_SIZE_ARCH 0
>>   #endif
>> @@ -439,6 +443,16 @@ struct mm_struct {
>>   	 */
>>   	struct hmm *hmm;
>>   #endif
>> +#if defined(CONFIG_HSA_RADEON) || defined(CONFIG_HSA_RADEON_MODULE)
>> +	/*
>> +	 * kfd always register an mmu_notifier we rely on mmu notifier to keep
>> +	 * refcount on mm struct as well as forbiding registering kfd on a
>> +	 * dying mm
>> +	 *
>> +	 * This field is set with mmap_sem old in write mode.
>> +	 */
>> +	struct kfd_process *kfd_process;
>> +#endif
>>   #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
>>   	pgtable_t pmd_huge_pte; /* protected by page_table_lock */
>>   #endif
>> --
>> 1.9.1
>>

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