aspeed-video WARN_ON in dma_free_attrs with 5.2

[Jae Hyun Yoo]

On 7/7/2019 9:15 PM, Joel Stanley wrote:
> I am running with Jae's fixes from dev-5.1 applied to 5.2.. I see this
> on boot, early on as userspace is coming up. The host is not running.
> 
>   WARNING: CPU: 0 PID: 140 at kernel/dma/mapping.c:281 dma_free_attrs+0xd0/0xe0
> 
> The driver is calling dma_free_attrs from aspeed_video_release. The
> comment in dma_free_attrs says:
> 
>          /*
>           * On non-coherent platforms which implement DMA-coherent buffers via
>           * non-cacheable remaps, ops->free() may call vunmap(). Thus getting
>           * this far in IRQ context is a) at risk of a BUG_ON() or trying to
>           * sleep on some machines, and b) an indication that the driver is
>           * probably misusing the coherent API anyway.
>           */
>          WARN_ON(irqs_disabled());
> 
> Which suggests aspeed-video might be at fault.
> 
> I can reproduce it in qemu. It does not reproduce with vanilla 5.2,
> which does not contain Jae's various fixes.

Hi Joel,

Thanks for reporting the issue.
I'll check it on dev-5.2 and will share the result.

Regards,
Jae

> Cheers,
> 
> Joel
> 
> ---
> 
> [   18.348693] ------------[ cut here ]------------
> [   18.353384] WARNING: CPU: 0 PID: 140 at kernel/dma/mapping.c:281
> dma_free_attrs+0xd0/0xe0
> [   18.361575] CPU: 0 PID: 140 Comm: v4l_id Not tainted
> 5.2.0-00110-ga3c857653fe9 #2
> [   18.369054] Hardware name: Generic DT based system
> [   18.373839] Backtrace:
> [   18.376328] [<80107e10>] (dump_backtrace) from [<80108044>]
> (show_stack+0x20/0x24)
> [   18.383902]  r7:0012c000 r6:00000009 r5:00000000 r4:00000000
> [   18.389583] [<80108024>] (show_stack) from [<8069dbe4>]
> (dump_stack+0x20/0x28)
> [   18.396833] [<8069dbc4>] (dump_stack) from [<80118930>]
> (__warn.part.3+0xb4/0xdc)
> [   18.404330] [<8011887c>] (__warn.part.3) from [<80118ad0>]
> (warn_slowpath_null+0x50/0x5c)
> [   18.412498]  r6:80158c28 r5:00000119 r4:807e2d78
> [   18.417136] [<80118a80>] (warn_slowpath_null) from [<80158c28>]
> (dma_free_attrs+0xd0/0xe0)
> [   18.425395]  r6:96100000 r5:9e125210 r4:80701904
> [   18.430031] [<80158b58>] (dma_free_attrs) from [<804f6500>]
> (aspeed_video_release+0xf8/0x138)
> [   18.438555]  r8:00000000 r7:20000013 r6:946a6cc0 r5:9456d4a0 r4:9456d000
> [   18.445267] [<804f6408>] (aspeed_video_release) from [<804d4050>]
> (v4l2_release+0xd4/0xe8)
> [   18.453530]  r8:95da1770 r7:946f2310 r6:945852a8 r5:946a6cc0 r4:9456d318
> [   18.460245] [<804d3f7c>] (v4l2_release) from [<80245448>] (__fput+0x98/0x1d0)
> [   18.467374]  r5:000a001d r4:946a6cc0
> [   18.470962] [<802453b0>] (__fput) from [<802455e8>] (____fput+0x18/0x1c)
> [   18.477668]  r10:80a03008 r9:95003fb0 r8:80101204 r7:00000000
> r6:80a65ab4 r5:947f5040
> [   18.485484]  r4:947f537c
> [   18.488028] [<802455d0>] (____fput) from [<80134af4>]
> (task_work_run+0x7c/0xa0)
> [   18.495350] [<80134a78>] (task_work_run) from [<801069d8>]
> (do_work_pending+0x484/0x598)
> [   18.503439]  r7:00000000 r6:05200001 r5:80101204 r4:ffffe000
> [   18.509106] [<80106554>] (do_work_pending) from [<8010106c>]
> (slow_work_pending+0xc/0x20)
> [   18.517277] Exception stack(0x95003fb0 to 0x95003ff8)
> [   18.522333] 3fa0:                                     00000000
> 00000000 00000001 00000000
> [   18.530507] 3fc0: 00000000 76f75330 05200001 00000006 00000000
> 00000000 43690fa4 00000000
> [   18.538676] 3fe0: 00023fd8 7ee50c18 00010edc 43801f70 60000010 00000003
> [   18.545293]  r10:00000006 r9:95002000 r8:80101204 r7:00000006
> r6:05200001 r5:76f75330
> [   18.553109]  r4:00000000
> [   18.555643] ---[ end trace fd1729fd68c24eef ]---
> [   18.560573] ------------[ cut here ]------------
>