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From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: ankitprasad.r.sharma@intel.com, intel-gfx@lists.freedesktop.org,
	akash.goel@intel.com, shashidhar.hiremath@intel.com
Subject: Re: [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects
Date: Wed, 22 Jul 2015 17:17:24 +0100	[thread overview]
Message-ID: <55AFC214.4060104@linux.intel.com> (raw)
In-Reply-To: <20150722160530.GE16722@phenom.ffwll.local>


On 07/22/2015 05:05 PM, Daniel Vetter wrote:
> On Wed, Jul 22, 2015 at 04:46:00PM +0100, Tvrtko Ursulin wrote:
>> But also, why it is even necessary to drop the mutex here?
>
> Locking inversion with our own pagefault handler. Happens since at least
> mesa can return gtt mmaps to gl clients, which can then in turn try to
> upload that with pwrite somewhere else. Also userspace could be just plain
> nasty and try to deadlock the kernel ;-)

Yeah blame userspace. ;D

> Dropping the struct_mutex is SOP for the copy_from/to_user slowpath.

I suspected something like that but did not feel like thinking too much. 
:) When encountering unusual things like dropping and re-acquiring locks 
I expect to see comments explaining it.

Regards,

Tvrtko
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  reply	other threads:[~2015-07-22 16:17 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-22 13:51 [PATCH v5 0/4] Support for creating/using Stolen memory backed objects ankitprasad.r.sharma
2015-07-22 13:51 ` [PATCH 1/4] drm/i915: Clearing buffer objects via CPU/GTT ankitprasad.r.sharma
2015-07-22 15:01   ` Tvrtko Ursulin
2015-07-22 15:05     ` Chris Wilson
2015-07-22 15:06     ` Chris Wilson
2015-07-22 15:16       ` Tvrtko Ursulin
2015-07-22 15:23         ` Chris Wilson
2015-07-22 13:51 ` [PATCH 2/4] drm/i915: Support for creating Stolen memory backed objects ankitprasad.r.sharma
2015-07-22 15:14   ` Tvrtko Ursulin
2015-07-22 15:27     ` Chris Wilson
2015-07-22 13:51 ` [PATCH 3/4] drm/i915: Add support for stealing purgable stolen pages ankitprasad.r.sharma
2015-07-22 15:10   ` Chris Wilson
2015-07-27  9:38   ` Daniel Vetter
2015-07-29 12:04     ` Chris Wilson
2015-07-31 14:42       ` Goel, Akash
2015-07-31 15:06         ` Chris Wilson
2015-07-31 16:34           ` Goel, Akash
2015-07-31 14:24     ` Goel, Akash
2015-07-22 13:51 ` [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem backed objects ankitprasad.r.sharma
2015-07-22 14:39   ` Chris Wilson
2015-07-31 13:16     ` Goel, Akash
2015-09-10 17:50       ` Ankitprasad Sharma
2015-09-15  9:58       ` Chris Wilson
2015-07-22 15:46   ` Tvrtko Ursulin
2015-07-22 16:05     ` Daniel Vetter
2015-07-22 16:17       ` Tvrtko Ursulin [this message]
  -- strict thread matches above, loose matches on Subject: below --
2015-09-15  8:33 [PATCH v6 0/4] Support for creating/using Stolen memory " ankitprasad.r.sharma
2015-09-15  8:33 ` [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem " ankitprasad.r.sharma
2015-09-15  9:54   ` Chris Wilson
2015-09-15 10:35     ` Ankitprasad Sharma
2015-07-01  9:25 [PATCH v4 0/4] Support for creating/using Stolen memory " ankitprasad.r.sharma
2015-07-01  9:25 ` [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem " ankitprasad.r.sharma
2015-07-01  9:54   ` Chris Wilson
2015-07-02 10:42   ` Tvrtko Ursulin
2015-07-02 11:00     ` Chris Wilson
2015-07-02 11:27       ` Tvrtko Ursulin
2015-07-02 11:58         ` Chris Wilson
2015-07-03  5:07   ` shuang.he
2015-05-06 10:15 [PATCH v3 0/4] Support for creating/using Stolen memory " ankitprasad.r.sharma
2015-05-06 10:16 ` [PATCH 4/4] drm/i915: Support for pread/pwrite from/to non shmem " ankitprasad.r.sharma

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