[PATCH 3.17 106/319] drm/i915: Do not store the error pointer for a failed userptr registration

From: Greg Kroah-Hartman
Date: Tue Nov 11 2014 - 20:25:54 EST

3.17-stable review patch. If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit e9681366ea9e76ab8f75e84351f2f3ca63ee542c upstream.

If we fail to create our mmu notification, we report the error back and
currently store the error inside the i915_mm_struct. This not only causes
subsequent registerations of the same mm to fail (an issue if the first
was interrupted by a signal and needed to be restarted) but also causes
us to eventually try and free the error pointer.

[ 73.419599] BUG: unable to handle kernel NULL pointer dereference at 000000000000004c
[ 73.419831] IP: [<ffffffff8114af33>] mmu_notifier_unregister+0x23/0x130
[ 73.420065] PGD 8650c067 PUD 870bb067 PMD 0
[ 73.420319] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
[ 73.420580] CPU: 0 PID: 42 Comm: kworker/0:1 Tainted: G W 3.17.0-rc6+ #1561
[ 73.420837] Hardware name: Intel Corporation SandyBridge Platform/LosLunas CRB, BIOS ASNBCPT1.86C.0075.P00.1106281639 06/28/2011
[ 73.421405] Workqueue: events __i915_mm_struct_free__worker
[ 73.421724] task: ffff880088a81220 ti: ffff880088168000 task.ti: ffff880088168000
[ 73.422051] RIP: 0010:[<ffffffff8114af33>] [<ffffffff8114af33>] mmu_notifier_unregister+0x23/0x130
[ 73.422410] RSP: 0018:ffff88008816bd50 EFLAGS: 00010286
[ 73.422765] RAX: 0000000000000003 RBX: ffff880086485400 RCX: 0000000000000000
[ 73.423137] RDX: ffff88016d80ee90 RSI: ffff880086485400 RDI: 0000000000000044
[ 73.423513] RBP: ffff88008816bd70 R08: 0000000000000001 R09: 0000000000000000
[ 73.423895] R10: 0000000000000320 R11: 0000000000000001 R12: 0000000000000044
[ 73.424282] R13: ffff880166e5f008 R14: ffff88016d815200 R15: ffff880166e5f040
[ 73.424682] FS: 0000000000000000(0000) GS:ffff88016d800000(0000) knlGS:0000000000000000
[ 73.425099] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 73.425537] CR2: 000000000000004c CR3: 0000000087f5f000 CR4: 00000000000407f0
[ 73.426157] Stack:
[ 73.426597] ffff880088a81248 ffff880166e5f038 fffffffffffffffc ffff880166e5f008
[ 73.427096] ffff88008816bd98 ffffffff814a75f2 ffff880166e5f038 ffff8800880f8a28
[ 73.427603] ffff88016d812ac0 ffff88008816be00 ffffffff8106321a ffffffff810631af
[ 73.428119] Call Trace:
[ 73.428606] [<ffffffff814a75f2>] __i915_mm_struct_free__worker+0x42/0x80
[ 73.429116] [<ffffffff8106321a>] process_one_work+0x1ba/0x610
[ 73.429632] [<ffffffff810631af>] ? process_one_work+0x14f/0x610
[ 73.430153] [<ffffffff810636db>] worker_thread+0x6b/0x4a0
[ 73.430671] [<ffffffff8108d67d>] ? trace_hardirqs_on+0xd/0x10
[ 73.431501] [<ffffffff81063670>] ? process_one_work+0x610/0x610
[ 73.432030] [<ffffffff8106a206>] kthread+0xf6/0x110
[ 73.432561] [<ffffffff8106a110>] ? __kthread_parkme+0x80/0x80
[ 73.433100] [<ffffffff8169c22c>] ret_from_fork+0x7c/0xb0
[ 73.433644] [<ffffffff8106a110>] ? __kthread_parkme+0x80/0x80
[ 73.434194] Code: 0f 1f 84 00 00 00 00 00 66 66 66 66 90 8b 46 4c 85 c0 0f 8e 10 01 00 00 55 48 89 e5 41 55 41 54 53 48 89 f3 49 89 fc 48 83 ec 08 <48> 83 7f 08 00 0f 84 b1 00 00 00 48 c7 c7 40 e6 ac 82 e8 26 65
[ 73.435942] RIP [<ffffffff8114af33>] mmu_notifier_unregister+0x23/0x130
[ 73.437017] RSP <ffff88008816bd50>
[ 73.437704] CR2: 000000000000004c

Fixes regression from commit ad46cb533d586fdb256855437af876617c6cf609
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Thu Aug 7 14:20:40 2014 +0100

drm/i915: Prevent recursive deadlock on releasing a busy userptr

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=84207
Testcase: igt/gem_render_copy_redux
Testcase: igt/gem_userptr_blits/create-destroy-sync
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Jacek Danecki <jacek.danecki@xxxxxxxxx>
Cc: "Gong, Zhipeng" <zhipeng.gong@xxxxxxxxx>
Cc: Jacek Danecki <jacek.danecki@xxxxxxxxx>
Cc: "Ursulin, Tvrtko" <tvrtko.ursulin@xxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/gpu/drm/i915/i915_gem_userptr.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -293,15 +293,23 @@ i915_gem_userptr_release__mmu_notifier(s
static struct i915_mmu_notifier *
i915_mmu_notifier_find(struct i915_mm_struct *mm)
{
- if (mm->mn == NULL) {
- down_write(&mm->mm->mmap_sem);
- mutex_lock(&to_i915(mm->dev)->mm_lock);
- if (mm->mn == NULL)
- mm->mn = i915_mmu_notifier_create(mm->mm);
- mutex_unlock(&to_i915(mm->dev)->mm_lock);
- up_write(&mm->mm->mmap_sem);
+ struct i915_mmu_notifier *mn = mm->mn;
+
+ mn = mm->mn;
+ if (mn)
+ return mn;
+
+ down_write(&mm->mm->mmap_sem);
+ mutex_lock(&to_i915(mm->dev)->mm_lock);
+ if ((mn = mm->mn) == NULL) {
+ mn = i915_mmu_notifier_create(mm->mm);
+ if (!IS_ERR(mn))
+ mm->mn = mn;
}
- return mm->mn;
+ mutex_unlock(&to_i915(mm->dev)->mm_lock);
+ up_write(&mm->mm->mmap_sem);
+
+ return mn;
}

static int


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