On 09/01/2023 19:12, Marijn Suijten wrote:
On 2023-01-09 11:06:45, Dmitry Baryshkov wrote:
On Mon, 9 Jan 2023 at 10:24, Marijn Suijten
<marijn.suijten@xxxxxxxxxxxxxx> wrote:
On 2023-01-09 01:30:29, Dmitry Baryshkov wrote:
On 09/01/2023 01:28, Dmitry Baryshkov wrote:
On 22/12/2022 01:19, Marijn Suijten wrote:
In the event that the topology requests resources that have not been
created by the system (because they are typically not represented in
dpu_mdss_cfg ^1), the resource(s) in global_state (in this case DSC
blocks) remain NULL but will still be returned out of
dpu_rm_get_assigned_resources, where the caller expects to get an array
containing num_blks valid pointers (but instead gets these NULLs).
To prevent this from happening, where null-pointer dereferences
typically result in a hard-to-debug platform lockup, num_blks shouldn't
increase past NULL blocks and will print an error and break instead.
After all, max_blks represents the static size of the maximum number of
blocks whereas the actual amount varies per platform.
^1: which can happen after a git rebase ended up moving additions to
_dpu_cfg to a different struct which has the same patch context.
Fixes: bb00a452d6f7 ("drm/msm/dpu: Refactor resource manager")
Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 5 +++++
1 file changed, 5 insertions(+)
I think the patch is not fully correct. Please check resource
availability during allocation. I wouldn't expect an error from
get_assigned_resources because of resource exhaustion.
Theoretically patch 5/8 should take care of this, and we should never
reach this failure condition. Emphasis on /should/, this may happen
again if/when another block type is added with sub-par resource
allocation and assignment implementation.
Yeah. Maybe swapping 4/8 and 5/8 makes sense.
Ack.
Another option, since allocation functions (except DSC) already have
these safety checks: check error message to mention internal
inconstency: allocated resource doesn't exist.
Is this a suggestion for the wording of the error message?
Yes. Because the current message makes one think that it is output
during allocation / assignment to encoder, while this is a safety net.
Good. So the patch is correct, just the wording is off, which I fully
agree on. This isn't allocating anything, just handing out what was
previously allocated (and is a safety net).
Yes. Please excuse me if my original message was not 100% clear.
- Marijn
--
With best wishes
Dmitry
