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From: Ben Widawsky <ben@bwidawsk.net>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 24/30] drm/i915: Refactor pwrite/pread to use single copy of get_user_pages
Date: Thu, 14 Apr 2011 16:23:23 -0700	[thread overview]
Message-ID: <20110414232323.GA4118@lundgren.kumite> (raw)
In-Reply-To: <1bdc18$k77tdj@fmsmga002.fm.intel.com>

On Wed, Apr 13, 2011 at 08:56:26PM +0100, Chris Wilson wrote:
> On Wed, 13 Apr 2011 21:26:24 +0200, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Tue, Apr 12, 2011 at 09:31:52PM +0100, Chris Wilson wrote:
> > > Replace the three nearly identical copies of the code with a single
> > > function. And take advantage of the opportunity to do some
> > > micro-optimisation: avoid the vmalloc if at all possible and also avoid
> > > dropping the lock unless we are forced to acquire the mm semaphore.
> > 
> > One tiny nitpick: Perhaps put an api comment at the top of
> > gem_get_user_pages that this function drops the struct_mutex. That's not
> > something we normally do and could cause endless amounts of fun if
> > neglected.
> 
> How about:
> 
> /**
>  * Magically retrieves the pages for the user addr whilst holding the
>  * dev->struct_mutex.
>  *
>  * Since we can not take the mm semaphore whilst holding our dev->struct_mutex,
>  * due to the pre-existing lock dependency established by i915_gem_fault(),
>  * we have to perform some sleight-of-hand.
>  *
>  * First, we try the lockless variant of gup whilst continuing to hold the
>  * mutex. If that fails to get all the user pages, then we no choice but
>  * to acquire the mm semaphore (thus dropping the lock on dev->struct_mutex
>  * to do so). The dev->struct_mutex is then re-acquired before we return.
>  *
>  * Returns: an error code *and* the number of user pages acquired. Even
>  * on an error, you must iterate over the return pages and release them.
>  */
> 
> ?
> -Chris

I like this patch...

Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

  parent reply	other threads:[~2011-04-14 23:23 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-12 20:31 i915 next Chris Wilson
2011-04-12 20:31 ` [PATCH 01/30] drm/i915: Split the crtc_mode_set function along HAS_PCH_SPLIT() lines Chris Wilson
2011-04-12 20:31 ` [PATCH 02/30] drm/i915: Move the vblank pre/post modeset to the common crtc_mode_set Chris Wilson
2011-04-12 20:31 ` [PATCH 03/30] drm/i915: Remove the PCH paths from the pre-Ironlake crtc_mode_set() Chris Wilson
2011-04-12 20:31 ` [PATCH 04/30] drm/i915: Drop the eDP paths from the pre-Ironlake crtc_mode_set Chris Wilson
2011-04-12 20:31 ` [PATCH 05/30] drm/i915: Drop the remaining bit of Ironlake code from i9xx_crtc_mode_set() Chris Wilson
2011-04-12 20:31 ` [PATCH 06/30] drm/i915: Drop non-HAS_PCH_SPLIT() code from ironlake_crtc_mode_set() Chris Wilson
2011-04-12 20:31 ` [PATCH 07/30] drm/i915: Drop remaining pre-Ironlake " Chris Wilson
2011-04-12 20:31 ` [PATCH 08/30] drm/i915: Clean up leftover DPLL and LVDS register choice from pch split Chris Wilson
2011-04-12 20:31 ` [PATCH 09/30] drm/i915: Fold the DPLL limit defines into the structs that use them Chris Wilson
2011-04-12 20:31 ` [PATCH 10/30] drm/i915: fix ilk rc6 teardown locking Chris Wilson
2011-04-12 20:31 ` [PATCH 11/30] drm/1915: ringbuffer wait for idle function Chris Wilson
2011-04-12 20:31 ` [PATCH 12/30] drm/i915: fix rc6 initialization on Ironlake Chris Wilson
2011-04-12 20:31 ` [PATCH 13/30] drm/i915: re-enable rc6 for ironlake Chris Wilson
2011-04-12 20:31 ` [PATCH 14/30] drm/i915: use i915_enable_rc6 on SNB too Chris Wilson
2011-04-12 20:31 ` [PATCH 15/30] drm/i915: Rename agp_type to cache_level Chris Wilson
2011-04-13 15:57   ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 16/30] drm/i915: Mark the cursor and the overlay as being part of the display planes Chris Wilson
2011-04-13 16:00   ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 17/30] drm/i915: Do not clflush snooped objects Chris Wilson
2011-04-13 16:04   ` Daniel Vetter
2011-04-13 17:34     ` Chris Wilson
2011-04-13 20:47       ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 18/30] drm/i915: Add an interface to dynamically change the cache level Chris Wilson
2011-04-13 18:59   ` Daniel Vetter
2011-04-13 19:21     ` Chris Wilson
2011-04-13 22:27     ` [PATCH 1/3] drm/i915: Introduce i915_gem_object_finish_gpu() Chris Wilson
2011-04-13 22:27       ` [PATCH 2/3] drm/i915: Introduce i915_gem_object_finish_gtt() Chris Wilson
2011-04-13 22:27       ` [PATCH 3/3] drm/i915: Add an interface to dynamically change the cache level Chris Wilson
2011-04-12 20:31 ` [PATCH 19/30] drm/i915: Use the uncached domain for the display planes v2 Chris Wilson
2011-04-12 20:31 ` [PATCH 20/30] drm/i915: Use the CPU domain for snooped pwrites Chris Wilson
2011-04-12 20:31 ` [PATCH 21/30] drm/i915: Redirect GTT mappings to the CPU page if cache-coherent Chris Wilson
2011-04-13 15:57   ` Eric Anholt
2011-04-13 16:19     ` Chris Wilson
2011-04-13 18:35     ` [PATCH] " Chris Wilson
2011-04-13 19:13       ` Daniel Vetter
2011-04-13 19:47         ` Chris Wilson
2011-04-13 20:26         ` [PATCH] drm/i915: Prevent mmap access through the GTT of snooped pages Chris Wilson
2011-04-13 20:51           ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 22/30] drm/i915: Use the LLC mode on gen6 for everything but display Chris Wilson
2011-04-13 19:15   ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 23/30] drm/i915: Cache GT fifo count for SandyBridge Chris Wilson
2011-04-14  2:21   ` Ben Widawsky
2011-04-14  4:48     ` Ben Widawsky
2011-04-12 20:31 ` [PATCH 24/30] drm/i915: Refactor pwrite/pread to use single copy of get_user_pages Chris Wilson
2011-04-13 15:59   ` Eric Anholt
2011-04-13 17:24     ` Chris Wilson
2011-04-13 19:35       ` Eric Anholt
2011-04-13 19:26   ` Daniel Vetter
2011-04-13 19:56     ` Chris Wilson
2011-04-13 20:56       ` Daniel Vetter
2011-04-14 23:23       ` Ben Widawsky [this message]
2011-04-15  9:48         ` Paul Menzel
2011-04-16  8:03           ` Chris Wilson
2011-04-12 20:31 ` [PATCH 25/30] drm/i915: s/addr & ~PAGE_MASK/offset_in_page(addr)/ Chris Wilson
2011-04-12 20:31 ` [PATCH 26/30] drm/i915: Maintain fenced gpu access until we flush the fence Chris Wilson
2011-04-13 19:37   ` Daniel Vetter
2011-04-13 20:15     ` Chris Wilson
2011-04-13 20:58       ` Daniel Vetter
2011-04-13 21:37         ` Chris Wilson
2011-04-12 20:31 ` [PATCH 27/30] drm/i915: Invalidate fenced read domains upon flush Chris Wilson
2011-04-13 19:43   ` Daniel Vetter
2011-04-13 20:38     ` Chris Wilson
2011-04-13 21:02       ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 28/30] drm/i915: Pass the fence register number to be written Chris Wilson
2011-04-13 19:48   ` Daniel Vetter
2011-04-12 20:31 ` [PATCH 29/30] drm/i915: Track fence setup separately from fenced object lifetime Chris Wilson
2011-04-13 20:42   ` Daniel Vetter
2011-04-13 21:56     ` Chris Wilson
2011-04-12 20:31 ` [PATCH 30/30] drm/i915: Only print out the actual number of fences for i915_error_state Chris Wilson
2011-04-13  7:26 ` i915 next Chris Wilson

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