Re: [Intel-gfx] [PATCH v10 11/15] drm/atomic-helper: Set fence deadline for vblank

[Nathan Chancellor <nathan@kernel.org>]

Hi Rob,

On Wed, Mar 08, 2023 at 07:53:02AM -0800, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> For an atomic commit updating a single CRTC (ie. a pageflip) calculate
> the next vblank time, and inform the fence(s) of that deadline.
> 
> v2: Comment typo fix (danvet)
> v3: If there are multiple CRTCs, consider the time of the soonest vblank
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Rob Clark <robdclark@chromium.org>

I apologize if this has already been reported or fixed, I searched lore
but did not find anything.

This change as commit d39e48ca80c0 ("drm/atomic-helper: Set fence
deadline for vblank") in -next causes a hang while running LTP's
read_all test on /proc on my Ampere Altra system (it seems it is hanging
on a pagemap file?). Additionally, I have this splat in dmesg, which
seems related based on the call stack.

[   20.542591] fbcon: Taking over console
[   20.550772] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000074
[   20.550776] Mem abort info:
[   20.550777]   ESR = 0x0000000096000004
[   20.550779]   EC = 0x25: DABT (current EL), IL = 32 bits
[   20.550781]   SET = 0, FnV = 0
[   20.550782]   EA = 0, S1PTW = 0
[   20.550784]   FSC = 0x04: level 0 translation fault
[   20.550785] Data abort info:
[   20.550786]   ISV = 0, ISS = 0x00000004
[   20.550788]   CM = 0, WnR = 0
[   20.550789] user pgtable: 4k pages, 48-bit VAs, pgdp=0000080009d16000
[   20.550791] [0000000000000074] pgd=0000000000000000, p4d=0000000000000000
[   20.550796] Internal error: Oops: 0000000096000004 [#1] SMP
[   20.550800] Modules linked in: ip6table_nat tun nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rfkill ip_set nf_tables nfnetlink qrtr sunrpc binfmt_misc vfat fat xfs snd_usb_audio snd_hwdep snd_usbmidi_lib snd_seq snd_pcm snd_rawmidi snd_timer snd_seq_device snd soundcore joydev mc ipmi_ssif ipmi_devintf ipmi_msghandler arm_spe_pmu arm_cmn arm_dsu_pmu arm_dmc620_pmu cppc_cpufreq loop zram crct10dif_ce polyval_ce nvme polyval_generic ghash_ce sbsa_gwdt igb nvme_core ast nvme_common i2c_algo_bit xgene_hwmon gpio_dwapb scsi_dh_rdac scsi_dh_emc scsi_dh_alua ip6_tables ip_tables dm_multipath fuse
[   20.550869] CPU: 12 PID: 469 Comm: kworker/12:1 Not tainted 6.3.0-rc2-00008-gd39e48ca80c0 #1
[   20.550872] Hardware name: ADLINK AVA Developer Platform/AVA Developer Platform, BIOS TianoCore 2.04.100.07 (SYS: 2.06.20220308) 09/08/2022
[   20.550875] Workqueue: events fbcon_register_existing_fbs
[   20.550884] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   20.550888] pc : drm_crtc_next_vblank_start+0x2c/0x98
[   20.550894] lr : drm_atomic_helper_wait_for_fences+0x90/0x240
[   20.550898] sp : ffff80000d583960
[   20.550900] x29: ffff80000d583960 x28: ffff07ff8fc187b0 x27: 0000000000000000
[   20.550904] x26: ffff07ff99c08c00 x25: 0000000000000038 x24: ffff07ff99c0c000
[   20.550908] x23: 0000000000000001 x22: 0000000000000038 x21: 0000000000000000
[   20.550912] x20: ffff07ff9640a280 x19: 0000000000000000 x18: ffffffffffffffff
[   20.550915] x17: 0000000000000000 x16: ffffb24d2eece1c0 x15: 0000003038303178
[   20.550919] x14: 3032393100000048 x13: 0000000000000000 x12: 0000000000000000
[   20.550923] x11: 0000000000000000 x10: 0000000000000000 x9 : ffffb24d2eeeaca0
[   20.550926] x8 : ffff80000d583628 x7 : 0000080077783000 x6 : 0000000000000000
[   20.550930] x5 : ffff80000d584000 x4 : ffff07ff99c0c000 x3 : 0000000000000130
[   20.550934] x2 : 0000000000000000 x1 : ffff80000d5839c0 x0 : ffff07ff99c0cc08
[   20.550937] Call trace:
[   20.550939]  drm_crtc_next_vblank_start+0x2c/0x98
[   20.550942]  drm_atomic_helper_wait_for_fences+0x90/0x240
[   20.550946]  drm_atomic_helper_commit+0xb0/0x188
[   20.550949]  drm_atomic_commit+0xb0/0xf0
[   20.550953]  drm_client_modeset_commit_atomic+0x218/0x280
[   20.550957]  drm_client_modeset_commit_locked+0x64/0x1a0
[   20.550961]  drm_client_modeset_commit+0x38/0x68
[   20.550965]  __drm_fb_helper_restore_fbdev_mode_unlocked+0xb0/0xf8
[   20.550970]  drm_fb_helper_set_par+0x44/0x88
[   20.550973]  fbcon_init+0x1e0/0x4a8
[   20.550976]  visual_init+0xbc/0x118
[   20.550981]  do_bind_con_driver.isra.0+0x194/0x3a0
[   20.550984]  do_take_over_console+0x50/0x70
[   20.550987]  do_fbcon_takeover+0x74/0xf8
[   20.550989]  do_fb_registered+0x13c/0x158
[   20.550992]  fbcon_register_existing_fbs+0x78/0xc0
[   20.550995]  process_one_work+0x1ec/0x478
[   20.551000]  worker_thread+0x74/0x418
[   20.551002]  kthread+0xec/0x100
[   20.551005]  ret_from_fork+0x10/0x20
[   20.551011] Code: f9400004 b9409013 f940a082 9ba30a73 (b9407662) 
[   20.551013] ---[ end trace 0000000000000000 ]---

If there is any additional information that I can provide or patches I
can test, I am more than happy to do so.

Cheers,
Nathan

# bad: [4b0f4525dc4fe8af17b3daefe585f0c2eb0fe0a5] Add linux-next specific files for 20230331
# good: [b2bc47e9b2011a183f9d3d3454a294a938082fb9] Merge tag 'net-6.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
git bisect start '4b0f4525dc4fe8af17b3daefe585f0c2eb0fe0a5' 'b2bc47e9b2011a183f9d3d3454a294a938082fb9'
# good: [ed5f95f3349003d74a4a11b27b0f05d6794c382a] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git
git bisect good ed5f95f3349003d74a4a11b27b0f05d6794c382a
# bad: [85f7d1bfa30a05df2c9d8a0e9f6b1f23b4a6f13b] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux-dt.git
git bisect bad 85f7d1bfa30a05df2c9d8a0e9f6b1f23b4a6f13b
# bad: [fbd0f79f200f8e5cb73fb3d7b788de09a8f33a6f] Merge branch 'msm-next' of https://gitlab.freedesktop.org/drm/msm.git
git bisect bad fbd0f79f200f8e5cb73fb3d7b788de09a8f33a6f
# good: [90031bc33f7525f0cc7a9ef0b1df62a1a4463382] Merge tag 'amd-drm-next-6.4-2023-03-17' of https://gitlab.freedesktop.org/agd5f/linux into drm-next
git bisect good 90031bc33f7525f0cc7a9ef0b1df62a1a4463382
# good: [d4e04817db670083aed73de1fadd3b21758e69ba] drm/amdgpu: Return from switch early for EEPROM I2C address
git bisect good d4e04817db670083aed73de1fadd3b21758e69ba
# good: [70e360f9b548d99f959668d4f047d1363d42fe8e] drm: exynos: dsi: Consolidate component and bridge
git bisect good 70e360f9b548d99f959668d4f047d1363d42fe8e
# bad: [0b43595d0cbb06736d1e572e79e29a410a273573] Merge branch 'drm-next' of https://gitlab.freedesktop.org/agd5f/linux
git bisect bad 0b43595d0cbb06736d1e572e79e29a410a273573
# good: [fbb3b3500f76ec8b741bd2d0e761ca3e856ad924] dt-bindings: display: boe,tv101wum-nl6: document rotation
git bisect good fbb3b3500f76ec8b741bd2d0e761ca3e856ad924
# bad: [82bbec189ab34873688484cd14189a5392946fbb] Merge v6.3-rc4 into drm-next
git bisect bad 82bbec189ab34873688484cd14189a5392946fbb
# bad: [d39e48ca80c0960b039cb38633957f0040f63e1a] drm/atomic-helper: Set fence deadline for vblank
git bisect bad d39e48ca80c0960b039cb38633957f0040f63e1a
# good: [d7d5a21dd6b4706c04fbba5d25db8da5f25aab68] dma-buf/dma-resv: Add a way to set fence deadline
git bisect good d7d5a21dd6b4706c04fbba5d25db8da5f25aab68
# good: [f3823da7e4ba7d4781375c2bb786a8a78efc6591] drm/scheduler: Add fence deadline support
git bisect good f3823da7e4ba7d4781375c2bb786a8a78efc6591
# good: [b2c077d001b612b1f34f7e528b2dc6072bd6794e] drm/vblank: Add helper to get next vblank time
git bisect good b2c077d001b612b1f34f7e528b2dc6072bd6794e
# first bad commit: [d39e48ca80c0960b039cb38633957f0040f63e1a] drm/atomic-helper: Set fence deadline for vblank