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

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Message-ID: <20140717141216.GA1963@gmail.com>
Date:	Thu, 17 Jul 2014 10:12:18 -0400
From:	Jerome Glisse <j.glisse@...il.com>
To:	Oded Gabbay <oded.gabbay@....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 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


> 
> 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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