| From 07ceea7eeb3262edc75c9b4113a47ed46bbab6d9 Mon Sep 17 00:00:00 2001 |
| From: Chris Wilson <chris@chris-wilson.co.uk> |
| Date: Wed, 4 Sep 2013 10:45:50 +0100 |
| Subject: drm/i915: Hold an object reference whilst we shrink it |
| |
| Whilst running the shrinker, we need to hold a reference as we unbind |
| the objects, or else we may end up waiting for and retiring requests, |
| which in turn may result in this object being freed. |
| |
| This is very similar to the eviction code which also has to be very |
| careful to keep a reference to its objects as it retires and unbinds |
| them. |
| |
| Another similarity, that Ben pointed out, is that as we may call |
| retire-requests, the unbound_list is outside of our control. We must |
| only process a single element of that list at a time, that is we can not |
| rely on the "safe" next pointer being valid after a call to |
| i915_vma_unbind(). |
| |
| BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 |
| IP: [<ffffffffa0082892>] i915_gem_gtt_finish_object+0x68/0xbd [i915] |
| PGD 758d3067 PUD ac0d6067 PMD 0 |
| Oops: 0000 [#1] SMP |
| Modules linked in: dm_mod snd_hda_codec_realtek iTCO_wdt iTCO_vendor_support pcspkr snd_hda_intel i2c_i801 snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_timer snd lpc_ich mfd_core soundcore battery ac option usb_wwan usbserial uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core videodev i915 video button drm_kms_helper drm acpi_cpufreq mperf freq_table |
| CPU: 1 PID: 16835 Comm: fbo-maxsize Not tainted 3.11.0-rc7_nightlytop_8fdad4_20130902_+ #7977 |
| task: ffff8800712106d0 ti: ffff880028e4a000 task.ti: ffff880028e4a000 |
| RIP: 0010:[<ffffffffa0082892>] [<ffffffffa0082892>] i915_gem_gtt_finish_object+0x68/0xbd [i915] |
| RSP: 0018:ffff880028e4b9e8 EFLAGS: 00010246 |
| RAX: 0000000000000000 RBX: ffff880145734000 RCX: ffff880145735328 |
| RDX: ffff8801457353fc RSI: 0000000000000000 RDI: ffff88007597cc00 |
| RBP: ffff88007597cc00 R08: 0000000000000001 R09: ffff88014f257f00 |
| R10: ffffea0001d65f00 R11: 0000000000bba60b R12: ffff880149e5b000 |
| R13: ffff880145734001 R14: ffff88007597ccc8 R15: ffff88007597cc00 |
| FS: 00007ff5bc919740(0000) GS:ffff88014f240000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 0000000000000008 CR3: 0000000028f4c000 CR4: 00000000001407e0 |
| DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 |
| DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 |
| Stack: |
| 0000000000000000 ffff88007597cc00 ffff8801440d6840 0000000000000000 |
| ffff880145734000 ffffffffa007c854 0000000000000010 ffff88007597c900 |
| 0000000000018000 00000000004a1201 ffff88007597cc60 ffffffffa007d183 |
| Call Trace: |
| [<ffffffffa007c854>] ? i915_vma_unbind+0xe2/0x1d1 [i915] |
| [<ffffffffa007d183>] ? __i915_gem_shrink+0xf1/0x162 [i915] |
| [<ffffffffa007d2ee>] ? i915_gem_object_get_pages_gtt+0xfa/0x303 [i915] |
| [<ffffffffa00795f4>] ? i915_gem_object_get_pages+0x54/0x89 [i915] |
| [<ffffffffa007cbda>] ? i915_gem_object_pin+0x238/0x5ce [i915] |
| [<ffffffff812cba5f>] ? __sg_page_iter_next+0x2b/0x58 |
| [<ffffffffa0082056>] ? gen6_ppgtt_insert_entries+0xf2/0x114 [i915] |
| [<ffffffffa007fe4b>] ? i915_gem_execbuffer_reserve_vma.isra.13+0x79/0x18d [i915] |
| [<ffffffffa008017c>] ? i915_gem_execbuffer_reserve+0x21d/0x347 [i915] |
| [<ffffffffa0080bfb>] ? i915_gem_do_execbuffer.isra.17+0x4f3/0xe61 [i915] |
| [<ffffffffa00795f4>] ? i915_gem_object_get_pages+0x54/0x89 [i915] |
| [<ffffffffa007e405>] ? i915_gem_pwrite_ioctl+0x743/0x7a5 [i915] |
| [<ffffffffa0081a46>] ? i915_gem_execbuffer2+0x15e/0x1e4 [i915] |
| [<ffffffffa000e20d>] ? drm_ioctl+0x2a5/0x3c4 [drm] |
| [<ffffffffa00818e8>] ? i915_gem_execbuffer+0x37f/0x37f [i915] |
| [<ffffffff816f64c0>] ? __do_page_fault+0x3ab/0x449 |
| [<ffffffff810be3da>] ? do_mmap_pgoff+0x2b2/0x341 |
| [<ffffffff810e49be>] ? vfs_ioctl+0x1e/0x31 |
| [<ffffffff810e5194>] ? do_vfs_ioctl+0x3ad/0x3ef |
| [<ffffffff810e5224>] ? SyS_ioctl+0x4e/0x7e |
| [<ffffffff816f88d2>] ? system_call_fastpath+0x16/0x1b |
| Code: 52 0c a0 48 c7 c6 22 30 0d a0 31 c0 e8 ef 00 f9 ff bf c6 a7 00 00 e8 90 5d 24 e1 f6 85 13 01 00 00 10 75 44 48 8b 85 18 01 00 00 <8b> 50 08 48 8b 30 49 8b 84 24 88 02 00 00 48 89 c7 48 81 c7 98 |
| RIP [<ffffffffa0082892>] i915_gem_gtt_finish_object+0x68/0xbd [i915] |
| RSP <ffff880028e4b9e8> |
| CR2: 0000000000000008 |
| |
| Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68171 |
| Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> |
| Cc: stable@vger.kernel.org |
| [danvet: Bikeshed the comments a bit as discussed with Chris.] |
| Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| |
| (cherry picked from commit 57094f82465002fbde1447e2fd850e1179bf6d86) |
| Signed-off-by: Darren Hart <dvhart@linux.intel.com> |
| --- |
| drivers/gpu/drm/i915/i915_gem.c | 45 +++++++++++++++++++++++++++++++++++------ |
| 1 file changed, 39 insertions(+), 6 deletions(-) |
| |
| diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c |
| index 399e159016e2..f0884a949a1f 100644 |
| --- a/drivers/gpu/drm/i915/i915_gem.c |
| +++ b/drivers/gpu/drm/i915/i915_gem.c |
| @@ -1695,6 +1695,7 @@ static long |
| __i915_gem_shrink(struct drm_i915_private *dev_priv, long target, |
| bool purgeable_only) |
| { |
| + struct list_head still_bound_list; |
| struct drm_i915_gem_object *obj, *next; |
| long count = 0; |
| |
| @@ -1709,23 +1710,55 @@ __i915_gem_shrink(struct drm_i915_private *dev_priv, long target, |
| } |
| } |
| |
| - list_for_each_entry_safe(obj, next, &dev_priv->mm.bound_list, |
| - global_list) { |
| + /* |
| + * As we may completely rewrite the bound list whilst unbinding |
| + * (due to retiring requests) we have to strictly process only |
| + * one element of the list at the time, and recheck the list |
| + * on every iteration. |
| + */ |
| + INIT_LIST_HEAD(&still_bound_list); |
| + while (count < target && !list_empty(&dev_priv->mm.bound_list)) { |
| struct i915_vma *vma, *v; |
| |
| + obj = list_first_entry(&dev_priv->mm.bound_list, |
| + typeof(*obj), global_list); |
| + list_move_tail(&obj->global_list, &still_bound_list); |
| + |
| if (!i915_gem_object_is_purgeable(obj) && purgeable_only) |
| continue; |
| |
| + /* |
| + * Hold a reference whilst we unbind this object, as we may |
| + * end up waiting for and retiring requests. This might |
| + * release the final reference (held by the active list) |
| + * and result in the object being freed from under us. |
| + * in this object being freed. |
| + * |
| + * Note 1: Shrinking the bound list is special since only active |
| + * (and hence bound objects) can contain such limbo objects, so |
| + * we don't need special tricks for shrinking the unbound list. |
| + * The only other place where we have to be careful with active |
| + * objects suddenly disappearing due to retiring requests is the |
| + * eviction code. |
| + * |
| + * Note 2: Even though the bound list doesn't hold a reference |
| + * to the object we can safely grab one here: The final object |
| + * unreferencing and the bound_list are both protected by the |
| + * dev->struct_mutex and so we won't ever be able to observe an |
| + * object on the bound_list with a reference count equals 0. |
| + */ |
| + drm_gem_object_reference(&obj->base); |
| + |
| list_for_each_entry_safe(vma, v, &obj->vma_list, vma_link) |
| if (i915_vma_unbind(vma)) |
| break; |
| |
| - if (!i915_gem_object_put_pages(obj)) { |
| + if (i915_gem_object_put_pages(obj) == 0) |
| count += obj->base.size >> PAGE_SHIFT; |
| - if (count >= target) |
| - return count; |
| - } |
| + |
| + drm_gem_object_unreference(&obj->base); |
| } |
| + list_splice(&still_bound_list, &dev_priv->mm.bound_list); |
| |
| return count; |
| } |
| -- |
| 1.8.5.rc3 |
| |