Bug 92638

Summary: [bsw] i915_gem_context_free WARN_ON(!list_empty(&ppgtt->base.active_list))
Product: DRI Reporter: Chris Wilson <chris>
Component: DRM/IntelAssignee: Intel GFX Bugs mailing list <intel-gfx-bugs>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: intel-gfx-bugs
Version: DRI git   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: BSW/CHT i915 features: GEM/Other

Description Chris Wilson 2015-10-23 13:18:03 UTC 
Spotted whilst running igt/gem_concurrent_blit. Rare.

[   92.791996] WARNING: CPU: 0 PID: 1352 at drivers/gpu/drm/i915/i915_gem_context.c:144 i915_gem_context_free+0x1b5/0x1d0()
[   92.792010] WARN_ON(!list_empty(&ppgtt->base.active_list))
[   92.792018] CPU: 0 PID: 1352 Comm: gem_concurrent_ Not tainted 4.3.0-rc6+ #151
[   92.792034] Hardware name:                  /NUC5CPYB, BIOS PYBSWCEL.86A.0027.2015.0507.1758 05/07/2015
[   92.792047]  ffffffff818ee4f0 ffff880065e2fa88 ffffffff812602cf ffff880065e2fad0
[   92.792066]  ffff880065e2fac0 ffffffff8106b55d ffff88005386ec00 ffff880276275a00
[   92.792084]  ffff880037f34000 ffff880234822b50 ffff880275b441f8 ffff880065e2fb20
[   92.792103] Call Trace:
[   92.792115]  [<ffffffff812602cf>] dump_stack+0x44/0x55
[   92.792127]  [<ffffffff8106b55d>] warn_slowpath_common+0x7d/0xb0
[   92.792137]  [<ffffffff8106b60c>] warn_slowpath_fmt+0x4c/0x50
[   92.792147]  [<ffffffff813633b5>] i915_gem_context_free+0x1b5/0x1d0
[   92.792182]  [<ffffffff8137076b>] i915_gem_request_free+0xbb/0xc0
[   92.792193]  [<ffffffff81370d8e>] i915_gem_object_retire__read+0x1ee/0x280
[   92.792203]  [<ffffffff81372efb>] i915_gem_retire_requests_ring+0x7b/0x150
[   92.792213]  [<ffffffff813659b1>] i915_gem_execbuffer_reserve.isra.21+0x31/0x350
[   92.792225]  [<ffffffff8136680a>] i915_gem_do_execbuffer.isra.27+0x7aa/0x1330
[   92.792235]  [<ffffffff8137608d>] ? i915_gem_object_do_pin+0x47d/0xad0
[   92.792245]  [<ffffffff81377d6a>] ? i915_gem_pwrite_ioctl+0xda/0xb80
[   92.792254]  [<ffffffff81375ac9>] ? i915_gem_free_object+0x1f9/0x340
[   92.792263]  [<ffffffff81367f82>] i915_gem_execbuffer2+0xb2/0x240
[   92.792274]  [<ffffffff8131cac3>] drm_ioctl+0x143/0x510
[   92.792282]  [<ffffffff81367ed0>] ? i915_gem_execbuffer+0x2f0/0x2f0
[   92.792292]  [<ffffffff81099c63>] ? pick_next_task_fair+0x3d3/0x420
[   92.792303]  [<ffffffff811458b1>] ? __fput+0x161/0x1d0
[   92.792313]  [<ffffffff81155955>] do_vfs_ioctl+0x285/0x460
[   92.792323]  [<ffffffff81155b71>] SyS_ioctl+0x41/0x70
[   92.792334]  [<ffffffff810015a4>] ? prepare_exit_to_usermode+0x84/0xc0
[   92.792345]  [<ffffffff8150a997>] entry_SYSCALL_64_fastpath+0x12/0x6a
Comment 1 Chris Wilson 2015-10-23 13:19:35 UTC 
The WARN is indeed invalid in the current codebase.
Comment 2 Tvrtko Ursulin 2015-11-05 17:27:25 UTC 
For the record, proposed fix, although with a bit of disagreement on what is logical:

http://patchwork.freedesktop.org/patch/62884/
Comment 3 Chris Wilson 2016-08-10 07:59:07 UTC 
commit b0decaf75bd902a11c932005c88924947ac00b8c
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Aug 4 07:52:44 2016 +0100

    drm/i915: Track active vma requests
    
    Hook the vma itself into the i915_gem_request_retire() so that we can
    accurately track when a solitary vma is inactive (as opposed to having
    to wait for the entire object to be idle). This improves the interaction
    when using multiple contexts (with full-ppgtt) and eliminates some
    frequent list walking when retiring objects after a completed request.
    
    A side-effect is that we get an active vma reference for free. The
    consequence of this is shown in the next patch...

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