Re: [PATCH 1/2] drm/i915/gem: Remove object_is_locked assertion from unpin_from_display_plane

[Andi Shyti <andi.shyti@intel.com>]

Hi Chris,

On Mon, Apr 20, 2020 at 01:53:55PM +0100, Chris Wilson wrote:
> Since moving the obj->vma.list to a spin_lock, and the vm->bound_list to
> its vm->mutex, along with tracking shrinkable status under its own
> spinlock, we no long require the object to be locked by the caller.
> 
> This is fortunate as it appears we can be called with the lock along an
> error path in flipping:
> 
> <4> [139.942851] WARN_ON(debug_locks && !lock_is_held(&(&((obj)->base.resv)->lock.base)->dep_map))
> <4> [139.943242] WARNING: CPU: 0 PID: 1203 at drivers/gpu/drm/i915/gem/i915_gem_domain.c:405 i915_gem_object_unpin_from_display_plane+0x70/0x130 [i915]
> <4> [139.943263] Modules linked in: snd_hda_intel i915 vgem snd_hda_codec_realtek snd_hda_codec_generic coretemp snd_intel_dspcfg snd_hda_codec snd_hwdep snd_hda_core r8169 lpc_ich snd_pcm realtek prime_numbers [last unloaded: i915]
> <4> [139.943347] CPU: 0 PID: 1203 Comm: kms_flip Tainted: G     U            5.6.0-gd0fda5c2cf3f1-drmtip_474+ #1
> <4> [139.943363] Hardware name:  /D510MO, BIOS MOPNV10J.86A.0311.2010.0802.2346 08/02/2010
> <4> [139.943589] RIP: 0010:i915_gem_object_unpin_from_display_plane+0x70/0x130 [i915]
> <4> [139.943589] Code: 85 28 01 00 00 be ff ff ff ff 48 8d 78 60 e8 d7 9b f0 e2 85 c0 75 b9 48 c7 c6 50 b9 38 c0 48 c7 c7 e9 48 3c c0 e8 20 d4 e9 e2 <0f> 0b eb a2 48 c7 c1 08 bb 38 c0 ba 0a 01 00 00 48 c7 c6 88 a3 35
> <4> [139.943589] RSP: 0018:ffffb774c0603b48 EFLAGS: 00010282
> <4> [139.943589] RAX: 0000000000000000 RBX: ffff9a142fa36e80 RCX: 0000000000000006
> <4> [139.943589] RDX: 000000000000160d RSI: ffff9a142c1a88f8 RDI: ffffffffa434a64d
> <4> [139.943589] RBP: ffff9a1410a513c0 R08: ffff9a142c1a88f8 R09: 0000000000000000
> <4> [139.943589] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9a1436ee94b8
> <4> [139.943589] R13: 0000000000000001 R14: 00000000ffffffff R15: ffff9a1410960000
> <4> [139.943589] FS:  00007fc73a744e40(0000) GS:ffff9a143da00000(0000) knlGS:0000000000000000
> <4> [139.943589] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> <4> [139.943589] CR2: 00007fc73997e098 CR3: 000000002f5fe000 CR4: 00000000000006f0
> <4> [139.943589] Call Trace:
> <4> [139.943589]  intel_pin_and_fence_fb_obj+0x1c9/0x1f0 [i915]
> <4> [139.943589]  intel_plane_pin_fb+0x3f/0xd0 [i915]
> <4> [139.943589]  intel_prepare_plane_fb+0x13b/0x5c0 [i915]
> <4> [139.943589]  drm_atomic_helper_prepare_planes+0x85/0x110
> <4> [139.943589]  intel_atomic_commit+0xda/0x390 [i915]
> <4> [139.943589]  drm_atomic_helper_page_flip+0x9c/0xd0
> <4> [139.943589]  ? drm_event_reserve_init+0x46/0x60
> <4> [139.943589]  drm_mode_page_flip_ioctl+0x587/0x5d0
> 
> This completes the symmetry lost in commit 8b1c78e06e61 ("drm/i915: Avoid
> calling i915_gem_object_unbind holding object lock").
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1743
> Fixes: 8b1c78e06e61 ("drm/i915: Avoid calling i915_gem_object_unbind holding object lock")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Andi Shyti <andi.shyti@intel.com>
> Cc: <stable@vger.kernel.org> # v5.6+

Acked-by: Andi Shyti <andi.shyti@intel.com>

Andi