[PATCH] drm/buddy: fix issue that force_merge cannot free all roots
Matthew Auld
matthew.auld at intel.com
Fri Aug 9 10:09:58 UTC 2024
Hi,
On 08/08/2024 07:38, Lin.Cao wrote:
> If buddy manager have more than one roots and each root have sub-block
> need to be free. When drm_buddy_fini called, the first loop of
> force_merge will merge and free all of the sub block of first root,
> which offset is 0x0 and size is biggest(more than have of the mm size).
> In subsequent force_merge rounds, if we use 0 as start and use remaining
> mm size as end, the block of other roots will be skipped in
> __force_merge function. It will cause the other roots can not be freed.
>
> Solution: use roots' offset as the start could fix this issue.
>
> Signed-off-by: Lin.Cao <lincao12 at amd.com>
Nice catch.
> ---
> drivers/gpu/drm/drm_buddy.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index 94f8c34fc293..5379687552bc 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -327,12 +327,14 @@ void drm_buddy_fini(struct drm_buddy *mm)
> u64 root_size, size;
> unsigned int order;
> int i;
> + u64 start = 0;
Nit: We could maybe move this into root_size, size or even into the loop
body below? Also no need to init.
>
> size = mm->size;
>
> for (i = 0; i < mm->n_roots; ++i) {
> order = ilog2(size) - ilog2(mm->chunk_size);
> - __force_merge(mm, 0, size, order);
> + start = drm_buddy_block_offset(mm->roots[i]);
> + __force_merge(mm, start, start + size, order);
>
> WARN_ON(!drm_buddy_block_is_free(mm->roots[i]));
We do seem to have a testcase for this at the bottom of
drm_test_buddy_alloc_clear(), so either it is not triggering the
WARN_ON() here in which case we should maybe improve that. Or it is, but
kunit doesn't treat that as a test failure? Maybe we can call something
like kunit_fail_current_test() here if that WARN_ON is triggered?
For reference our CI is just running all drm selftests with:
/kernel/tools/testing/kunit/kunit.py run --kunitconfig
/kernel/drivers/gpu/drm/tests/.kunitconfig
> drm_block_free(mm, mm->roots[i]);
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