linux-kernel - [PATCH 0/2] module: add -EEXIST module

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Message-Id: <20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa782a@samsung.com>
Date: Thu, 18 Dec 2025 21:59:43 +0100
From: Daniel Gomez <da.gomez@...nel.org>
To: Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>, 
 Daniel Gomez <da.gomez@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
 Aaron Tomlin <atomlin@...mlin.com>, Jonathan Corbet <corbet@....net>, 
 Lucas De Marchi <demarchi@...nel.org>
Cc: linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-doc@...r.kernel.org, Daniel Gomez <da.gomez@...sung.com>
Subject: [PATCH 0/2] module: add -EEXIST module_init() reservation docs

This series documents the -EEXIST error code reservation in the module
loader, building on Lucas's patches [1] that add the runtime safety net.

When module_init() returns -EEXIST, kmod interprets this as "module
already loaded" and reports success, hiding real init failures. Lucas's
patches warn and override this to -EBUSY. These patches document this
convention to prevent future cases.

This was originally reported in this thread [2].

Link: https://lore.kernel.org/all/20251013-module-warn-ret-v1-0-ab65b41af01f@intel.com/ [1]
Link: https://lore.kernel.org/all/aKEVQhJpRdiZSliu@orbyte.nwl.cc/#t [2]

Signed-off-by: Daniel Gomez <da.gomez@...sung.com>
---
Daniel Gomez (2):
      module: add -EEXIST documentation
      docs: hacking: clarify reserved -EEXIST in module_init()

 Documentation/kernel-hacking/hacking.rst | 7 +++++++
 kernel/module/main.c                     | 8 ++++++++
 2 files changed, 15 insertions(+)
---
base-commit: e5f0a698b34ed76002dc5cff3804a61c80233a7a
change-id: 20251218-dev-module-init-eexists-modules-docs-1dc7cb7a96bb
prerequisite-change-id: 20251013-module-warn-ret-59f085298055:v1
prerequisite-patch-id: c3e4f5b5d01c2b48b4c94e51a60469cb74691853
prerequisite-patch-id: 2d5a726a75f3b9d9c256b8478fb6115a92f04354

Best regards,
--  
Daniel Gomez <da.gomez@...sung.com>