From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tvrtko Ursulin Subject: Re: [PATCH] drm/i915: Do not store the error pointer for a failed userptr registration Date: Fri, 26 Sep 2014 10:51:54 +0100 Message-ID: <5425373A.809@linux.intel.com> References: <1411723862-7782-1-git-send-email-chris@chris-wilson.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTP id ADA406E1AE for ; Fri, 26 Sep 2014 02:51:56 -0700 (PDT) In-Reply-To: <1411723862-7782-1-git-send-email-chris@chris-wilson.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Chris Wilson , intel-gfx@lists.freedesktop.org Cc: stable@vger.kernel.org List-Id: intel-gfx@lists.freedesktop.org On 09/26/2014 10:31 AM, Chris Wilson wrote: > 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: [] 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:[] [] 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] [] __i915_mm_struct_free__worker+0x42/0x80 > [ 73.429116] [] process_one_work+0x1ba/0x610 > [ 73.429632] [] ? process_one_work+0x14f/0x610 > [ 73.430153] [] worker_thread+0x6b/0x4a0 > [ 73.430671] [] ? trace_hardirqs_on+0xd/0x10 > [ 73.431501] [] ? process_one_work+0x610/0x610 > [ 73.432030] [] kthread+0xf6/0x110 > [ 73.432561] [] ? __kthread_parkme+0x80/0x80 > [ 73.433100] [] ret_from_fork+0x7c/0xb0 > [ 73.433644] [] ? __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 [] mmu_notifier_unregister+0x23/0x130 > [ 73.437017] RSP > [ 73.437704] CR2: 000000000000004c > > Fixes regression from commit ad46cb533d586fdb256855437af876617c6cf609 > Author: Chris Wilson > 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 > Cc: Jacek Danecki > Cc: "Gong, Zhipeng" > Cc: Jacek Danecki > Cc: "Ursulin, Tvrtko" > Cc: stable@vger.kernel.org > --- > drivers/gpu/drm/i915/i915_gem_userptr.c | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c > index 903a875..ecd5c84 100644 > --- 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(struct drm_i915_gem_object *obj) > 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 > Reviewed-by: Tvrtko Ursulin