[bisected] Re: nouveau: lockdep cli->mutex vs reservation_ww_class_mutex deadlock report

[Mike Galbraith <efault@gmx.de>]

This little bugger bisected to...

	b73cd1e2ebfc "drm/ttm: stop destroying pinned ghost object"

...and (the second time around) was confirmed on the spot.  However,
while the fingered commit still reverts cleanly, doing so at HEAD does
not make lockdep return to happy camper state (leading to bisection
#2), ie the fingered commit is only the beginning of nouveau's 5.12
cycle lockdep woes.

homer:..kernel/linux-master # quilt applied|grep revert
patches/revert-drm-ttm-Remove-pinned-bos-from-LRU-in-ttm_bo_move_to_lru_tail-v2.patch
patches/revert-drm-ttm-cleanup-LRU-handling-further.patch
patches/revert-drm-ttm-use-pin_count-more-extensively.patch
patches/revert-drm-ttm-stop-destroying-pinned-ghost-object.patch

That still ain't enough to appease lockdep at HEAD.  I'm not going to
muck about with it beyond that, since this looks a whole lot like yet
another example of "fixing stuff exposes other busted stuff".

On Wed, 2021-03-10 at 10:58 +0100, Mike Galbraith wrote:
> [   29.966927] ======================================================
> [   29.966929] WARNING: possible circular locking dependency detected
> [   29.966932] 5.12.0.g05a59d7-master #2 Tainted: G        W   E
> [   29.966934] ------------------------------------------------------
> [   29.966937] X/2145 is trying to acquire lock:
> [   29.966939] ffff888120714518 (&cli->mutex){+.+.}-{3:3}, at: nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.967002]
>                but task is already holding lock:
> [   29.967004] ffff888123c201a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: nouveau_bo_pin+0x2b/0x310 [nouveau]
> [   29.967053]
>                which lock already depends on the new lock.
>
> [   29.967056]
>                the existing dependency chain (in reverse order) is:
> [   29.967058]
>                -> #1 (reservation_ww_class_mutex){+.+.}-{3:3}:
> [   29.967063]        __ww_mutex_lock.constprop.16+0xbe/0x10d0
> [   29.967069]        nouveau_bo_pin+0x2b/0x310 [nouveau]
> [   29.967112]        nouveau_channel_prep+0x106/0x2e0 [nouveau]
> [   29.967151]        nouveau_channel_new+0x4f/0x760 [nouveau]
> [   29.967188]        nouveau_abi16_ioctl_channel_alloc+0xdf/0x350 [nouveau]
> [   29.967223]        drm_ioctl_kernel+0x91/0xe0 [drm]
> [   29.967245]        drm_ioctl+0x2db/0x380 [drm]
> [   29.967259]        nouveau_drm_ioctl+0x56/0xb0 [nouveau]
> [   29.967303]        __x64_sys_ioctl+0x76/0xb0
> [   29.967307]        do_syscall_64+0x33/0x40
> [   29.967310]        entry_SYSCALL_64_after_hwframe+0x44/0xae
> [   29.967314]
>                -> #0 (&cli->mutex){+.+.}-{3:3}:
> [   29.967318]        __lock_acquire+0x1494/0x1ac0
> [   29.967322]        lock_acquire+0x23e/0x3b0
> [   29.967325]        __mutex_lock+0x95/0x9d0
> [   29.967330]        nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.967377]        ttm_bo_handle_move_mem+0x79/0x130 [ttm]
> [   29.967384]        ttm_bo_validate+0x156/0x1b0 [ttm]
> [   29.967390]        nouveau_bo_validate+0x48/0x70 [nouveau]
> [   29.967438]        nouveau_bo_pin+0x1de/0x310 [nouveau]
> [   29.967487]        nv50_wndw_prepare_fb+0x53/0x4d0 [nouveau]
> [   29.967531]        drm_atomic_helper_prepare_planes+0x8a/0x110 [drm_kms_helper]
> [   29.967547]        nv50_disp_atomic_commit+0xa9/0x1b0 [nouveau]
> [   29.967593]        drm_atomic_helper_update_plane+0x10a/0x150 [drm_kms_helper]
> [   29.967606]        drm_mode_cursor_universal+0x10b/0x220 [drm]
> [   29.967627]        drm_mode_cursor_common+0x190/0x200 [drm]
> [   29.967648]        drm_mode_cursor_ioctl+0x3d/0x50 [drm]
> [   29.967669]        drm_ioctl_kernel+0x91/0xe0 [drm]
> [   29.967684]        drm_ioctl+0x2db/0x380 [drm]
> [   29.967699]        nouveau_drm_ioctl+0x56/0xb0 [nouveau]
> [   29.967748]        __x64_sys_ioctl+0x76/0xb0
> [   29.967752]        do_syscall_64+0x33/0x40
> [   29.967756]        entry_SYSCALL_64_after_hwframe+0x44/0xae
> [   29.967760]
>                other info that might help us debug this:
>
> [   29.967764]  Possible unsafe locking scenario:
>
> [   29.967767]        CPU0                    CPU1
> [   29.967770]        ----                    ----
> [   29.967772]   lock(reservation_ww_class_mutex);
> [   29.967776]                                lock(&cli->mutex);
> [   29.967779]                                lock(reservation_ww_class_mutex);
> [   29.967783]   lock(&cli->mutex);
> [   29.967786]
>                 *** DEADLOCK ***
>
> [   29.967790] 3 locks held by X/2145:
> [   29.967792]  #0: ffff88810365bcf8 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_mode_cursor_common+0x87/0x200 [drm]
> [   29.967817]  #1: ffff888108d9e098 (crtc_ww_class_mutex){+.+.}-{3:3}, at: drm_modeset_lock+0xc3/0xe0 [drm]
> [   29.967841]  #2: ffff888123c201a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: nouveau_bo_pin+0x2b/0x310 [nouveau]
> [   29.967896]
>                stack backtrace:
> [   29.967899] CPU: 6 PID: 2145 Comm: X Kdump: loaded Tainted: G        W   E     5.12.0.g05a59d7-master #2
> [   29.967904] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
> [   29.967908] Call Trace:
> [   29.967911]  dump_stack+0x6d/0x89
> [   29.967915]  check_noncircular+0xe7/0x100
> [   29.967919]  ? nvkm_vram_map+0x48/0x50 [nouveau]
> [   29.967959]  ? __lock_acquire+0x1494/0x1ac0
> [   29.967963]  __lock_acquire+0x1494/0x1ac0
> [   29.967967]  lock_acquire+0x23e/0x3b0
> [   29.967971]  ? nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.968020]  __mutex_lock+0x95/0x9d0
> [   29.968024]  ? nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.968070]  ? nvif_vmm_map+0xf4/0x110 [nouveau]
> [   29.968093]  ? nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.968137]  ? lock_release+0x160/0x280
> [   29.968141]  ? nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.968184]  nouveau_bo_move+0x11f/0x980 [nouveau]
> [   29.968226]  ? up_write+0x17/0x130
> [   29.968229]  ? unmap_mapping_pages+0x53/0x110
> [   29.968234]  ttm_bo_handle_move_mem+0x79/0x130 [ttm]
> [   29.968240]  ttm_bo_validate+0x156/0x1b0 [ttm]
> [   29.968247]  nouveau_bo_validate+0x48/0x70 [nouveau]
> [   29.968289]  nouveau_bo_pin+0x1de/0x310 [nouveau]
> [   29.968330]  nv50_wndw_prepare_fb+0x53/0x4d0 [nouveau]
> [   29.968372]  drm_atomic_helper_prepare_planes+0x8a/0x110 [drm_kms_helper]
> [   29.968384]  ? lockdep_init_map_type+0x58/0x240
> [   29.968388]  nv50_disp_atomic_commit+0xa9/0x1b0 [nouveau]
> [   29.968430]  drm_atomic_helper_update_plane+0x10a/0x150 [drm_kms_helper]
> [   29.968442]  drm_mode_cursor_universal+0x10b/0x220 [drm]
> [   29.968463]  ? lock_is_held_type+0xdd/0x130
> [   29.968468]  drm_mode_cursor_common+0x190/0x200 [drm]
> [   29.968486]  ? drm_mode_setplane+0x190/0x190 [drm]
> [   29.968502]  drm_mode_cursor_ioctl+0x3d/0x50 [drm]
> [   29.968518]  drm_ioctl_kernel+0x91/0xe0 [drm]
> [   29.968533]  drm_ioctl+0x2db/0x380 [drm]
> [   29.968548]  ? drm_mode_setplane+0x190/0x190 [drm]
> [   29.968570]  ? _raw_spin_unlock_irqrestore+0x30/0x60
> [   29.968574]  ? lockdep_hardirqs_on+0x79/0x100
> [   29.968578]  ? _raw_spin_unlock_irqrestore+0x3b/0x60
> [   29.968582]  nouveau_drm_ioctl+0x56/0xb0 [nouveau]
> [   29.968632]  __x64_sys_ioctl+0x76/0xb0
> [   29.968636]  ? lockdep_hardirqs_on+0x79/0x100
> [   29.968640]  do_syscall_64+0x33/0x40
> [   29.968644]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [   29.968648] RIP: 0033:0x7f1ccfb4e9e7
> [   29.968652] Code: b3 66 90 48 8b 05 b1 14 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 81 14 2c 00 f7 d8 64 89 01 48
> [   29.968659] RSP: 002b:00007ffca9596058 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [   29.968663] RAX: ffffffffffffffda RBX: 000055da9d0c6470 RCX: 00007f1ccfb4e9e7
> [   29.968667] RDX: 00007ffca9596090 RSI: 00000000c01c64a3 RDI: 000000000000000e
> [   29.968670] RBP: 00007ffca9596090 R08: 0000000000000040 R09: 000055da9d0f6310
> [   29.968674] R10: 0000000000000093 R11: 0000000000000246 R12: 00000000c01c64a3
> [   29.968677] R13: 000000000000000e R14: 0000000000000000 R15: 0000000000000000
>