Re: [PATCH] drm/amd/display: use GFP_ATOMIC for bounding box

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 04.06.24 um 15:50 schrieb Alex Deucher:
> This can be called in atomic context.  Should fix:
>
> BUG: sleeping function called from invalid context at include/linux/sched/mm.h:306
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 449, name: kworker/u64:8
> preempt_count: 2, expected: 0
> RCU nest depth: 0, expected: 0
> Preemption disabled at:
> ffffffffc0ce1580>] dc_fpu_begin+0x30/0xd0 [amdgpu]
> CPU: 5 PID: 449 Comm: kworker/u64:8 Tainted: G        W          6.8.0+ #35
> Hardware name: System manufacturer System Product Name/ROG STRIX X570-E GAMING WIFI II, BIOS 4204 02/24/2022
> Workqueue: events_unbound async_run_entry_fn

That most likely only papers over the real problem and is not a valid fix.

The question is why is that an atomic context?  If the function is used 
under a spinlock then this might indeed be the right fix.

If it's because of floating point operation then that here won't work 
either.

In that case the only real fix is to avoid the allocation altogether.

Regards,
Christian.

>
> Fixes: 88c61827cedc ("drm/amd/display: dynamically allocate dml2_configuration_options structures")
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> Cc: George Zhang <george.zhang@amd.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: harry.wentland@amd.com
> Cc: sunpeng.li@amd.com
> Cc: Rodrigo.Siqueira@amd.com
> ---
>   drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c  | 2 +-
>   .../gpu/drm/amd/display/dc/resource/dcn321/dcn321_resource.c    | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
> index 0f11d7c8791c..3fe0d5334145 100644
> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
> @@ -2009,7 +2009,7 @@ static void dcn32_update_bw_bounding_box(struct dc *dc, struct clk_bw_params *bw
>   {
>   	struct dml2_configuration_options *dml2_opt;
>   
> -	dml2_opt = kmemdup(&dc->dml2_options, sizeof(dc->dml2_options), GFP_KERNEL);
> +	dml2_opt = kmemdup(&dc->dml2_options, sizeof(dc->dml2_options), GFP_ATOMIC);
>   	if (!dml2_opt)
>   		return;
>   
> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn321/dcn321_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn321/dcn321_resource.c
> index 07ca6f58447d..a61cf5741275 100644
> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn321/dcn321_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn321/dcn321_resource.c
> @@ -1583,7 +1583,7 @@ static void dcn321_update_bw_bounding_box(struct dc *dc, struct clk_bw_params *b
>   {
>   	struct dml2_configuration_options *dml2_opt;
>   
> -	dml2_opt = kmemdup(&dc->dml2_options, sizeof(dc->dml2_options), GFP_KERNEL);
> +	dml2_opt = kmemdup(&dc->dml2_options, sizeof(dc->dml2_options), GFP_ATOMIC);
>   	if (!dml2_opt)
>   		return;
>