An out-of-tree GPU or storage kernel module stops building after a kernel upgrade

DKMS rebuilds out-of-tree modules against each new kernel, but it can only recompile the source it was given. When the kernel removes or renames an internal function the module calls, the rebuild fails with an implicit declaration error and the node comes back from its upgrade without GPUDirect, without its parallel filesystem client, or in some cases without a working driver at all.

Symptom

/var/lib/dkms/beegfs/8.1.0/build/build/../source/common/storage/RdmaInfo.c:58:13: error: implicit declaration of function 'ib_peer_memory_client_register'

Root cause

The kernel offers no stable internal API. Functions are renamed, moved between headers, or deleted between releases, and out-of-tree code that calls them has to be updated in step. DKMS automates recompilation, not adaptation, so it faithfully rebuilds source that no longer matches the target and reports the mismatch as a compiler error.

Recommended fix

Read the first error in the module's build log, not the last. The compiler names the exact symbol and usually suggests the replacement, which identifies whether this is a rename, a moved header, or a removal.

How Denpex helps

Denpex matches An out-of-tree GPU or storage kernel module stops building after a kernel upgrade across every rank in a distributed run and reports which rank failed first, so you act on the initiating node instead of the loudest one.

A post-upgrade build failure in which DKMS recompiles an out-of-tree kernel module against a kernel whose internal API has changed, so the module fails to compile or fails to load and the capability it provided disappears without an explicit alert.

Linux deliberately keeps no stable in-kernel API, so anything living outside the tree must track it. DKMS exists to rebuild those modules automatically and does exactly that, which means it will rebuild source the kernel has outgrown and surface the disagreement as a compile error. The upgrade succeeds from the package manager's point of view because the package is still installed; only the module is missing.

• A node reboots after routine patching and loses a capability nothing in the change record touched
• The failure is a compiler error in a log nobody reads, not an alert
• The module built correctly on this machine last month against the previous kernel
• Rolling the kernel back restores service, which makes the vendor look blameless and the kernel look at fault

• GPUDirect Storage and RDMA stacks, where peer-memory modules bridge the GPU driver and the fabric
• Parallel filesystem clients built as out-of-tree modules, including BeeGFS with GPU Direct support
• NVIDIA driver DKMS packages on distributions that ship kernels faster than the driver supports them
• Any cluster where unattended upgrades can move the kernel without moving the drivers with it

Use this checklist to test the hypothesis against a small reproduction. No single line proves the root cause, so preserve the preceding events and compare one variable at a time.

• ✓Open /var/lib/dkms/<module>/<version>/build/make.log and take the first error line; it names the symbol and the source file, which is the whole diagnosis.
• ✓Compare the running kernel against the versions the module's release notes claim support for. A kernel newer than anything the vendor lists is the answer.
• ✓Check whether the module is loaded at all. A module that failed to rebuild leaves the package installed, so package state is not evidence that the capability exists.

• The kernel offers no stable internal API. Functions are renamed, moved between headers, or deleted between releases, and out-of-tree code that calls them has to be updated in step. DKMS automates recompilation, not adaptation, so it faithfully rebuilds source that no longer matches the target and reports the mismatch as a compiler error.
• A missing declaration is fatal rather than a warning because the build treats implicit function declarations as errors. That is deliberate: a silently assumed signature would produce a module that loads and then corrupts memory, which is far worse on a node holding GPU mappings.
• The blast radius is wider than the module because these components sit under a capability rather than an application. A peer-memory module that fails to build does not announce that GPUDirect is gone; the fabric simply falls back to a slower path, or the mount that needed it is absent, and the first symptom is a performance or availability change nobody connects to a patch.

/var/lib/dkms/beegfs/8.1.0/build/build/../source/common/storage/RdmaInfo.c:58:13: error: implicit declaration of function 'ib_peer_memory_client_register'
modprobe: ERROR: could not insert 'nvidia_peermem': Invalid argument
dmesg: nvidia_peermem: Unknown symbol ib_register_peer_memory_client

Use this text as a lookup key in logs and upstream issue trackers. It is not presented as a captured customer log. Confirm the cause from your own preceding events, versions, configuration and the cited references.

Moving to a module release built for the running kernel supplies source that calls functions which exist, so the rebuild completes and the capability returns. Correcting the install order for peer-memory components works on the same principle from the linking side: the driver can only bind to fabric symbols that were present when it built.

Select the traceback or open the failed terminal, then run Denpex locally to see the initiating rank, collateral failures, exact fix, and verification command without uploading the log.