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* [PATCH] drm/rockchip: fix VOP vblank race
@ 2018-03-28 16:03 ` John Keeping
  0 siblings, 0 replies; 10+ messages in thread
From: John Keeping @ 2018-03-28 16:03 UTC (permalink / raw)
  To: dri-devel
  Cc: linux-rockchip, John Keeping, Sandy Huang, linux-arm-kernel,
	Heiko Stübner

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>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index 6755a9eea4b2..d4e1400aedf3 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);
 	}
 }
 
-- 
2.16.3

^ permalink raw reply related	[flat|nested] 10+ messages in thread
* [PATCH] drm/rockchip: fix VOP vblank race
@ 2018-03-28 16:03 ` John Keeping
  0 siblings, 0 replies; 10+ messages in thread
From: John Keeping @ 2018-03-28 16:03 UTC (permalink / raw)
  To: linux-arm-kernel

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>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index 6755a9eea4b2..d4e1400aedf3 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);
 	}
 }
 
-- 
2.16.3

^ permalink raw reply related	[flat|nested] 10+ messages in thread
* Re: [PATCH] drm/rockchip: fix VOP vblank race
  2018-03-28 16:03 ` John Keeping
@ 2018-04-10 12:40   ` Sandy Huang
  -1 siblings, 0 replies; 10+ messages in thread
From: Sandy Huang @ 2018-04-10 12:40 UTC (permalink / raw)
  To: John Keeping
  Cc: linux-rockchip, dri-devel, Heiko Stübner, linux-arm-kernel

Reviewed-by: Sandy huang <hjc@rock-chips.com>

在 2018/3/29 0:03, John Keeping 写道:
> 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>
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 6755a9eea4b2..d4e1400aedf3 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);
>   	}
>   }
>   



_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 10+ messages in thread
* [PATCH] drm/rockchip: fix VOP vblank race
@ 2018-04-10 12:40   ` Sandy Huang
  0 siblings, 0 replies; 10+ messages in thread
From: Sandy Huang @ 2018-04-10 12:40 UTC (permalink / raw)
  To: linux-arm-kernel

Reviewed-by: Sandy huang <hjc@rock-chips.com>

? 2018/3/29 0:03, John Keeping ??:
> 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>
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 6755a9eea4b2..d4e1400aedf3 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);
>   	}
>   }
>   

^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] drm/rockchip: fix VOP vblank race
  2018-04-10 12:40   ` Sandy Huang
@ 2018-04-16 16:46     ` John Keeping
  -1 siblings, 0 replies; 10+ messages in thread
From: John Keeping @ 2018-04-16 16:46 UTC (permalink / raw)
  To: Sandy Huang; +Cc: linux-rockchip, dri-devel, linux-arm-kernel

Hi Sandy,

On Tue, 10 Apr 2018 20:40:06 +0800, Sandy Huang wrote:

> Reviewed-by: Sandy huang <hjc@rock-chips.com>

Thanks for the review, but I don't see this in drm-misc yet.  Are you
planning to pick this up?

> 在 2018/3/29 0:03, John Keeping 写道:
> > 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>
> > ---
> >   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > index 6755a9eea4b2..d4e1400aedf3 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);
> >   	}
> >   }
> >     
> 
> 
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

^ permalink raw reply	[flat|nested] 10+ messages in thread
* [PATCH] drm/rockchip: fix VOP vblank race
@ 2018-04-16 16:46     ` John Keeping
  0 siblings, 0 replies; 10+ messages in thread
From: John Keeping @ 2018-04-16 16:46 UTC (permalink / raw)
  To: linux-arm-kernel

Hi Sandy,

On Tue, 10 Apr 2018 20:40:06 +0800, Sandy Huang wrote:

> Reviewed-by: Sandy huang <hjc@rock-chips.com>

Thanks for the review, but I don't see this in drm-misc yet.  Are you
planning to pick this up?

> ? 2018/3/29 0:03, John Keeping ??:
> > 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>
> > ---
> >   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > index 6755a9eea4b2..d4e1400aedf3 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);
> >   	}
> >   }
> >     
> 
> 

^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] drm/rockchip: fix VOP vblank race
  2018-04-16 16:46     ` John Keeping
@ 2018-04-16 21:43       ` Heiko Stuebner
  -1 siblings, 0 replies; 10+ messages in thread
From: Heiko Stuebner @ 2018-04-16 21:43 UTC (permalink / raw)
  To: John Keeping; +Cc: linux-rockchip, dri-devel, linux-arm-kernel

Hi John,

Am Montag, 16. April 2018, 18:46:56 CEST schrieb John Keeping:
> Hi Sandy,
> 
> On Tue, 10 Apr 2018 20:40:06 +0800, Sandy Huang wrote:
> 
> > Reviewed-by: Sandy huang <hjc@rock-chips.com>
> 
> Thanks for the review, but I don't see this in drm-misc yet.  Are you
> planning to pick this up?

I was occupied with merge-window stuff recently, but I guess either
Sandy or myself is going to pick it up shortly.


Heiko

> > 在 2018/3/29 0:03, John Keeping 写道:
> > > 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>
> > > ---
> > >   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > > index 6755a9eea4b2..d4e1400aedf3 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);
> > >   	}
> > >   }
> > >     
> > 
> > 
> 


_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

^ permalink raw reply	[flat|nested] 10+ messages in thread
* [PATCH] drm/rockchip: fix VOP vblank race
@ 2018-04-16 21:43       ` Heiko Stuebner
  0 siblings, 0 replies; 10+ messages in thread
From: Heiko Stuebner @ 2018-04-16 21:43 UTC (permalink / raw)
  To: linux-arm-kernel

Hi John,

Am Montag, 16. April 2018, 18:46:56 CEST schrieb John Keeping:
> Hi Sandy,
> 
> On Tue, 10 Apr 2018 20:40:06 +0800, Sandy Huang wrote:
> 
> > Reviewed-by: Sandy huang <hjc@rock-chips.com>
> 
> Thanks for the review, but I don't see this in drm-misc yet.  Are you
> planning to pick this up?

I was occupied with merge-window stuff recently, but I guess either
Sandy or myself is going to pick it up shortly.


Heiko

> > ? 2018/3/29 0:03, John Keeping ??:
> > > 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>
> > > ---
> > >   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > > index 6755a9eea4b2..d4e1400aedf3 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);
> > >   	}
> > >   }
> > >     
> > 
> > 
> 

^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] drm/rockchip: fix VOP vblank race
  2018-04-16 21:43       ` Heiko Stuebner
@ 2018-04-17  1:28         ` Sandy Huang
  -1 siblings, 0 replies; 10+ messages in thread
From: Sandy Huang @ 2018-04-17  1:28 UTC (permalink / raw)
  To: Heiko Stuebner, John Keeping; +Cc: linux-rockchip, linux-arm-kernel, dri-devel

Applied to drm-misc-next. Thanks！


在 2018/4/17 5:43, Heiko Stuebner 写道:
> Hi John,
>
> Am Montag, 16. April 2018, 18:46:56 CEST schrieb John Keeping:
>> Hi Sandy,
>>
>> On Tue, 10 Apr 2018 20:40:06 +0800, Sandy Huang wrote:
>>
>>> Reviewed-by: Sandy huang <hjc@rock-chips.com>
>> Thanks for the review, but I don't see this in drm-misc yet.  Are you
>> planning to pick this up?
> I was occupied with merge-window stuff recently, but I guess either
> Sandy or myself is going to pick it up shortly.
>
>
> Heiko
>
>>> 在 2018/3/29 0:03, John Keeping 写道:
>>>> 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>
>>>> ---
>>>>    drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>> index 6755a9eea4b2..d4e1400aedf3 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);
>>>>    	}
>>>>    }
>>>>      
>>>
>
>
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> Linux-rockchip@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip


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^ permalink raw reply	[flat|nested] 10+ messages in thread
* [PATCH] drm/rockchip: fix VOP vblank race
@ 2018-04-17  1:28         ` Sandy Huang
  0 siblings, 0 replies; 10+ messages in thread
From: Sandy Huang @ 2018-04-17  1:28 UTC (permalink / raw)
  To: linux-arm-kernel

Applied to drm-misc-next. Thanks?


? 2018/4/17 5:43, Heiko Stuebner ??:
> Hi John,
>
> Am Montag, 16. April 2018, 18:46:56 CEST schrieb John Keeping:
>> Hi Sandy,
>>
>> On Tue, 10 Apr 2018 20:40:06 +0800, Sandy Huang wrote:
>>
>>> Reviewed-by: Sandy huang <hjc@rock-chips.com>
>> Thanks for the review, but I don't see this in drm-misc yet.  Are you
>> planning to pick this up?
> I was occupied with merge-window stuff recently, but I guess either
> Sandy or myself is going to pick it up shortly.
>
>
> Heiko
>
>>> ? 2018/3/29 0:03, John Keeping ??:
>>>> 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>
>>>> ---
>>>>    drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>> index 6755a9eea4b2..d4e1400aedf3 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);
>>>>    	}
>>>>    }
>>>>      
>>>
>
>
> _______________________________________________
> Linux-rockchip mailing list
> Linux-rockchip at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip

^ permalink raw reply	[flat|nested] 10+ messages in thread
end of thread, other threads:[~2018-04-17  1:28 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-03-28 16:03 [PATCH] drm/rockchip: fix VOP vblank race John Keeping
2018-03-28 16:03 ` John Keeping
2018-04-10 12:40 ` Sandy Huang
2018-04-10 12:40   ` Sandy Huang
2018-04-16 16:46   ` John Keeping
2018-04-16 16:46     ` John Keeping
2018-04-16 21:43     ` Heiko Stuebner
2018-04-16 21:43       ` Heiko Stuebner
2018-04-17  1:28       ` Sandy Huang
2018-04-17  1:28         ` Sandy Huang

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