Describe the bug

Exporting patches from repo_b/rpi-6.18.y and applying them onto linux-6.18.y does not reproduce the final tree state of repo_b/rpi-6.18.y. rpi-6.18.y refers to the official raspberry pi repo on github. linux-6.18.y is the official repo on kernel.org repo_b is a local copy of raspberrypi repo (git remote add repo_b https://github.com/raspberrypi/linux.git)

The specific observed mismatch is in:

drivers/gpu/drm/v3d/v3d_submit.c

The source branch repo_b/rpi-6.18.y contains:

ret = v3d_job_init(v3d, file_priv, &cpu_job->base,
                   v3d_cpu_job_free, 0, &se, V3D_CPU);

After exporting/applying the patch series onto linux-6.18.y, the resulting tree contains:

ret = v3d_job_init(v3d, file_priv, &cpu_job->base,
                   v3d_job_free, 0, &se, V3D_CPU);

This is incorrect relative to the source branch.

You can reproduce it with this steps:

Starting from the repository containing both branches:

git log --reverse --oneline linux-6.18.y..repo_b/rpi-6.18.y -- drivers/gpu/drm/v3d/v3d_submit.c

Observed output:

e741376342f0 drm/v3d: Clock V3D down when not in use.
37c0c660d4d8 [DOWNSTREAM] drm/v3d: Delete downstream CLK management
8a87e9a48987 [BACKPORTED] drm/v3d: Introduce Runtime Power Management
b9ec35c5945b Merge remote-tracking branch 'stable/linux-6.18.y' into rpi-6.18.y
3d40d37b968c Merge remote-tracking branch 'stable/linux-6.18.y' into rpi-6.18.y

After applying the exported patches onto linux-6.18.y, the corresponding applied branch shows no commit touching this file:

git log --reverse --oneline linux-6.18.y..HEAD -- drivers/gpu/drm/v3d/v3d_submit.c

Observed output:

<no output>

The final source branch differs from linux-6.18.y for this file:

git diff --stat linux-6.18.y..repo_b/rpi-6.18.y -- drivers/gpu/drm/v3d/v3d_submit.c

Observed output:

drivers/gpu/drm/v3d/v3d_submit.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)

Commit-level analysis

The relevant source history is:

e741376342f0  drm/v3d: Clock V3D down when not in use.
37c0c660d4d8  [DOWNSTREAM] drm/v3d: Delete downstream CLK management
3d40d37b968c  Merge remote-tracking branch 'stable/linux-6.18.y' into rpi-6.18.y

Commit e741376342f0 changes the CPU job free callback from:

v3d_job_free

to:

v3d_cpu_job_free

Commit 37c0c660d4d8 later changes it back from:

v3d_cpu_job_free

to:

v3d_job_free

The source branch is corrected again by merge commit:

3d40d37b968c590b949cb732e0d435c0dccd8ed0

This can be reproduced with:

git log --reverse -m -p -G 'v3d_(cpu_)?job_free.*V3D_CPU' linux-6.18.y..repo_b/rpi-6.18.y -- drivers/gpu/drm/v3d/v3d_submit.c

Relevant observed output from merge commit 3d40d37b968c:

+static void
+v3d_cpu_job_free(struct kref *ref)
+{
+       struct v3d_cpu_job *job = container_of(ref, struct v3d_cpu_job,
+                                              base.refcount);
+
+       v3d_timestamp_query_info_free(&job->timestamp_query,
+                                     job->timestamp_query.count);
+
+       v3d_performance_query_info_free(&job->performance_query,
+                                       job->performance_query.count);
+
+       if (job->indirect_csd.indirect)
+               drm_gem_object_put(job->indirect_csd.indirect);
+
+       v3d_job_free(ref);
+}

and:

 ret = v3d_job_init(v3d, file_priv, &cpu_job->base,
-                   v3d_job_free, 0, &se, V3D_CPU);
+                   v3d_cpu_job_free, 0, &se, V3D_CPU);

Therefore, the correction exists in the source branch as part of a merge-resolution diff, not as a normal non-merge commit.

Cause

The exported patch series did not preserve the merge-resolution change from:

3d40d37b968c590b949cb732e0d435c0dccd8ed0

As a result, replaying the exported patches reproduces the earlier bad state introduced by:

37c0c660d4d8 [DOWNSTREAM] drm/v3d: Delete downstream CLK management

but does not reproduce the later correction made by the merge.

Expected result

After exporting patches from:

linux-6.18.y..repo_b/rpi-6.18.y

and applying them onto linux-6.18.y, the resulting tree should match repo_b/rpi-6.18.y, at least for:

drivers/gpu/drm/v3d/v3d_submit.c

The expected call is:

ret = v3d_job_init(v3d, file_priv, &cpu_job->base,
                   v3d_cpu_job_free, 0, &se, V3D_CPU);

Actual result

The applied patch series leaves the file with:

ret = v3d_job_init(v3d, file_priv, &cpu_job->base,
                   v3d_job_free, 0, &se, V3D_CPU);

This misses the final source-branch correction from merge commit 3d40d37b968c.

Verification commands

The missing merge-resolution change can be verified with:

git show -m --cc 3d40d37b968c -- drivers/gpu/drm/v3d/v3d_submit.c

or:

git log --reverse -m -p -G 'v3d_(cpu_)?job_free.*V3D_CPU' linux-6.18.y..repo_b/rpi-6.18.y -- drivers/gpu/drm/v3d/v3d_submit.c

The applied branch can be checked with:

grep -n -A4 -B4 'v3d_job_init(v3d, file_priv, &cpu_job->base' drivers/gpu/drm/v3d/v3d_submit.c

Expected source branch result:

v3d_cpu_job_free

Incorrect replayed result:

v3d_job_free

The missing merge-resolution hunk from 3d40d37b968c should be preserved when exporting/replaying the downstream patch series, or the correction should be represented as an explicit non-merge commit before patch export.

Steps to reproduce the behaviour

see above

Device (s)

Other

System

n.a.

Logs

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Additional context

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