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| author | John Keeping <john@metanate.com> | 2018-03-28 17:03:51 +0100 |
|---|---|---|
| committer | Sandy Huang <hjc@rock-chips.com> | 2018-04-17 09:18:16 +0800 |
| commit | 2d078c2d04a535c2f342beb84c59cdade5cfe3d3 (patch) | |
| tree | a84f1ead77de75b20add935ecf441bbb60a34395 | |
| parent | d50479ad314dc6eca438b95d38a44dd5f72dd7f7 (diff) | |
| download | linux-2d078c2d04a535c2f342beb84c59cdade5cfe3d3.tar.gz linux-2d078c2d04a535c2f342beb84c59cdade5cfe3d3.tar.bz2 linux-2d078c2d04a535c2f342beb84c59cdade5cfe3d3.zip | |
drm/rockchip: fix VOP vblank race
We have seen a case of a bad reference count for vblanks with the
Rockchip VOP:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 383 at drivers/gpu/drm/drm_irq.c:1198 drm_vblank_put+0x40/0xcc
Modules linked in: brcmfmac brcmutil
CPU: 1 PID: 383 Comm: kworker/u8:2 Not tainted 4.9.75-rt60 #1
Hardware name: Rockchip (Device Tree)
Workqueue: events_unbound flip_worker
Backtrace:
[<c010b7b0>] (dump_backtrace) from [<c010ba4c>] (show_stack+0x18/0x1c)
r7:c0b1b13c r6:600b0013 r5:00000000 r4:c0b1b13c
[<c010ba34>] (show_stack) from [<c032d248>] (dump_stack+0x78/0x94)
[<c032d1d0>] (dump_stack) from [<c011e6e8>] (__warn+0xe4/0x104)
r7:00000009 r6:c03cf26c r5:00000000 r4:00000000
[<c011e604>] (__warn) from [<c011e7c0>] (warn_slowpath_null+0x28/0x30)
r9:eeb443a0 r8:eeb443c8 r7:ee8a5ec0 r6:ee8a5ec0 r5:edb47f00 r4:ee096200
[<c011e798>] (warn_slowpath_null) from [<c03cf26c>] (drm_vblank_put+0x40/0xcc)
[<c03cf22c>] (drm_vblank_put) from [<c03cf310>] (drm_crtc_vblank_put+0x18/0x1c)
r5:edb47f00 r4:ee3c8a80
[<c03cf2f8>] (drm_crtc_vblank_put) from [<c03ef9b4>] (vop_fb_unref_worker+0x18/0x24)
[<c03ef99c>] (vop_fb_unref_worker) from [<c03df194>] (flip_worker+0x98/0xb4)
r5:edb47f00 r4:eeb443a8
[<c03df0fc>] (flip_worker) from [<c0134808>] (process_one_work+0x1a8/0x2fc)
r9:00000000 r8:ee807d00 r7:00000000 r6:ee809c00 r5:eeb443a8 r4:edfe5f80
[<c0134660>] (process_one_work) from [<c01358ec>] (worker_thread+0x2ac/0x458)
r10:00000088 r9:edfe5f98 r8:ee809c2c r7:c0b04100 r6:ee809c00 r5:ee809c00
r4:edfe5f80
[<c0135640>] (worker_thread) from [<c013a0bc>] (kthread+0xfc/0x10c)
r10:00000000 r9:00000000 r8:c0135640 r7:edfe5f80 r6:00000000 r5:edf0e240
r4:ee8a4000 r3:ed194e00
[<c0139fc0>] (kthread) from [<c0107cb8>] (ret_from_fork+0x14/0x3c)
r8:00000000 r7:00000000 r6:00000000 r5:c0139fc0 r4:edf0e240
---[ end trace 0000000000000002 ]---
It seems that this is caused by unfortunate timing between
vop_crtc_atomic_flush() and vop_handle_vblank() given the following
ordering:
atomic_flush handle_vblank
------------ -------------
drm_flip_work_queue
set_bit
if (test_and_clear_bit(...))
drm_flip_work_commit
drm_vblank_get
This results in vop_fb_unref_worker (called as flip work) decrementing
the vblank refcount before it has been incremented.
Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Sandy huang <hjc@rock-chips.com>
Signed-off-by: Sandy Huang <hjc@rock-chips.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180328160351.23763-1-john@metanate.com
| -rw-r--r-- | drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c index 53d4afe15278..510cdf076bb1 100644 --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c @@ -1017,9 +1017,9 @@ static void vop_crtc_atomic_flush(struct drm_crtc *crtc, continue; drm_framebuffer_get(old_plane_state->fb); + WARN_ON(drm_crtc_vblank_get(crtc) != 0); drm_flip_work_queue(&vop->fb_unref_work, old_plane_state->fb); set_bit(VOP_PENDING_FB_UNREF, &vop->pending); - WARN_ON(drm_crtc_vblank_get(crtc) != 0); } } |