[Intel-gfx] drm_mm crash with multi threads

[Rob Clark]

On Thu, Dec 22, 2016 at 11:07 PM, Mark yao <mark.yao at rock-chips.com> wrote:
> Hi Chris Wilson
>
> We port drm_mm to my internal kernel, with high load test, found following
> crash:
>
> [49451.856244]
> ==================================================================
> [49451.856350] BUG: KASAN: wild-memory-access on address dead000000000108
> [49451.856379] Write of size 8 by task Binder:218_4/683 [49451.856417] CPU:
> 2 PID: 683 Comm: Binder:218_4 Not tainted 4.4.36 #62 [49451.856443] Hardware
> name: Rockchip RK3399 Excavator Board edp (Android) (DT) [49451.856469] Call
> trace: [49451.856519] [<ffffff900808a9d0>] dump_backtrace+0x0/0x230
> [49451.856556] [<ffffff900808ac14>] show_stack+0x14/0x1c [49451.856592]
> [<ffffff90084a4de0>] dump_stack+0xa0/0xc8 [49451.856633]
> [<ffffff900821b700>] kasan_report+0x110/0x4dc [49451.856670]
> [<ffffff900821aa84>] __asan_store8+0x24/0x7c [49451.856715]
> [<ffffff90086158c4>] drm_mm_insert_node_generic+0x2dc/0x464 [49451.856760]
> [<ffffff90086406a8>] rockchip_gem_iommu_map+0x60/0x158 [49451.856794]
> [<ffffff9008640bb4>] rockchip_gem_create_object+0x278/0x488 [49451.856827]
> [<ffffff9008641020>] rockchip_gem_create_with_handle+0x24/0x10c
> [49451.856862] [<ffffff9008641364>] rockchip_gem_create_ioctl+0x3c/0x50
> [49451.856896] [<ffffff900860aee4>] drm_ioctl+0x354/0x52c [49451.856939]
> [<ffffff900823d948>] do_vfs_ioctl+0x670/0x78c [49451.856976]
> [<ffffff900823dac4>] SyS_ioctl+0x60/0x88 [49451.857009] [<ffffff9008082ef0>]
> el0_svc_naked+0x24/0x28
> We only use drm_mm_insert_node_generic to alloc memory, and use
> drm_mm_remove_node to release memory
>
> alloc/release maybe on difference threads.
>
> Seem the problem is threads problem, drm_mm seems is not threads safe, we
> found drm_mm_insert_node_generic and drm_mm_remove_node
> may access same resource with list ops, such as some mm->hole_stack.
>
> After use mutex lock protect drm_mm_remove_node and
> drm_mm_insert_node_generic, the crash disappear.
>
> I'm not familiar with drm mm, Do you know how to fix it?

I don't think drm_mm is intended to be thread safe, but instead the
driver should provide whatever locking is needed before calling in to
drm_mm.  (And presumably you already need some lock to protect driver
level data structures when creating/destroying gem objects.)

BR,
-R

> Thanks.
>
> On 2016年12月17日 03:25, Chris Wilson wrote:
>
> With a lot of polish applied, Joonas has reviewed the series - all but
> for [04/38] "lib: Add a simple prime number generator"
> [lib/prime_numbers.c]. Anyone feel like poking around at a bit of number
> theory?
>
> Other than it would appear to be ready for Daniel to sort out the merge
> between drm-misc/i915... Please do take a look and see if you can spot
> anything else that needs fixing/improving.
> -Chris
>
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>
> --
> Ｍark Yao
>
>
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