[Bug 103454] [IGT] drv_selftest/live_contexts WARN_ON(i915_gem_object_has_pinned_pages(obj))

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103454

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit f991c492aa55fb1c6834882c5d786d5bb3b25f07
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Nov 6 11:15:08 2017 +0000

    drm/i915: Lock llist_del_first() vs llist_del_all()

    An oversight in commit 87701b4b5593 ("drm/i915: Only free the oldest
    stale object before a fresh allocation") was that not only do we have to
    serialise concurrent users of llist_del_first(), but we also have to
    lock llist_del_first() vs llist_del_all().

    From llist.h,

     * This can be summarized as follows:
     *
     *           |   add    | del_first |  del_all
     * add       |    -     |     -     |     -
     * del_first |          |     L     |     L
     * del_all   |          |           |     -
     *
     * Where, a particular row's operation can happen concurrently with a
column's
     * operation, with "-" being no lock needed, while "L" being lock is
needed.

    This should hopefully explain:

    <4>[   89.287106] general protection fault: 0000 [#1] PREEMPT SMP
    <4>[   89.287126] Modules linked in: snd_hda_codec_hdmi
snd_hda_codec_realtek snd_hda_codec_generic x86_pkg_temp_thermal
intel_powerclamp coretemp i915 crct10dif_pclmul crc32_pclmul
ghash_clmulni_intel snd_hda_intel snd_hda_codec snd_hwdep snd_hda_core r8169
mii mei_me mei snd_pcm prime_numbers i2c_hid pinctrl_geminilake pinctrl_intel
    <4>[   89.287226] CPU: 2 PID: 23 Comm: ksoftirqd/2 Tainted: G     U        
 4.14.0-rc8-CI-CI_DRM_3315+ #1
    <4>[   89.287247] Hardware name: Intel Corp. Geminilake/GLK RVP2 LP4SD
(07), BIOS GELKRVPA.X64.0062.B30.1708222146 08/22/2017
    <4>[   89.287270] task: ffff88017ab34ec0 task.stack: ffffc90000128000
    <4>[   89.287290] RIP: 0010:llist_add_batch+0x4/0x20
    <4>[   89.287301] RSP: 0018:ffffc9000012bdb8 EFLAGS: 00010296
    <4>[   89.287314] RAX: ffffffff811017ad RBX: 6e468801a1560000 RCX:
ef3e53fceecdeb81
    <4>[   89.287330] RDX: 6e468801a1566130 RSI: ffff880103d73d98 RDI:
ffff880103d73d98
    <4>[   89.287346] RBP: ffffc9000012bdb8 R08: ffff88017ab35780 R09:
0000000000000000
    <4>[   89.287361] R10: ffffc9000012bd68 R11: 00000000abb18c3d R12:
ffffffffa01369e0
    <4>[   89.287377] R13: ffff88017fd1b8f8 R14: ffff88017ab34ec0 R15:
000000000000000a
    <4>[   89.287393] FS:  0000000000000000(0000) GS:ffff88017fd00000(0000)
knlGS:0000000000000000
    <4>[   89.287411] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    <4>[   89.287424] CR2: 00007ff0c0755018 CR3: 000000016df9b000 CR4:
00000000003406e0
    <4>[   89.287440] Call Trace:
    <4>[   89.287511]  __i915_gem_free_object_rcu+0x20/0x40 [i915]
    <4>[   89.287527]  rcu_process_callbacks+0x27a/0x730
    <4>[   89.287544]  __do_softirq+0xc0/0x4ae
    <4>[   89.287559]  ? smpboot_thread_fn+0x2d/0x280
    <4>[   89.287571]  run_ksoftirqd+0x1f/0x70
    <4>[   89.287582]  smpboot_thread_fn+0x18a/0x280
    <4>[   89.287595]  kthread+0x114/0x150
    <4>[   89.287605]  ? sort_range+0x30/0x30
    <4>[   89.287615]  ? kthread_create_on_node+0x40/0x40
    <4>[   89.287628]  ret_from_fork+0x27/0x40
    <4>[   89.287641] Code: 0d 48 83 ea 01 4c 89 c1 48 83 fa ff 74 12 48 23 0c
d7 74 ed 48 c1 e2 06 48 0f bd c9 48 8d 04 0a 5d c3 90 90 90 90 90 55 48 89 e5
<48> 8b 0a 48 89 0e 48 89 c8 f0 48 0f b1 3a 48 39 c1 75 ed 48 85
    <1>[   89.287774] RIP: llist_add_batch+0x4/0x20 RSP: ffffc9000012bdb8
    <4>[   89.287826] ---[ end trace e775d15174d8ae02 ]---

    (Lockless lists are only easy (and lockless) when only using
    llist_add/llist_del_all!)

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