[PATCH v2 0/6] devfreq: Add refcounts for governor modules

[Jie Zhan]

A governor module can be dynamically inserted or removed if compiled as a
kernel module.  'devfreq->governor' would become NULL if the governor
module is removed when it's in use.

For user-friendliness, get and put the module refcount of a governor module
when it's in use.  As a result, unloading a governor module in use returns
an error, e.g.:

$ cat governor
performance
$ rmmod governor_performance
rmmod: ERROR: Module governor_performance is in use

Note that this can't stop force unload, so it's more of a
user-friendliness improvement rather than strict protection.  The
existing code that keeps devfreq working when 'devfreq->governor' is
NULL should still be there.

Patch 1-3 clean up mutex with guards and factor out a common governor
setting function, so as to prepare for implementing governor reference
counting.  They can be applied separately.

Patch 4-6 add the reference counting mechanism for devfreq governor modules.

Changelog:
v2:
- Rebase on devfreq-next of 7.1-rc1.
- Drop the patches related to the NULL pointer deference issue of
  'devfreq->governor', which has been solved and merged recently.
- Remove the dedicated mutex for 'devfreq_governor_list' because the
  refcount changes don't depend on that.
- Some minor cleanups and fixes.

v1:
https://lore.kernel.org/all/20260326123428.800407-1-zhanjie9@hisilicon.com/

Jie Zhan (6):
  devfreq: Use mutex guard in governor_store()
  devfreq: Use mutex guard in devfreq_add/remove_governor()
  devfreq: Factor out devfreq_set_governor()
  devfreq: Add module owner to devfreq governor
  devfreq: Get and put module refcount when switching governor
  devfreq: Get module refcount in try_then_request_governor()

 drivers/devfreq/devfreq.c        | 210 +++++++++++++++----------------
 include/linux/devfreq-governor.h |  26 +++-
 2 files changed, 127 insertions(+), 109 deletions(-)

-- 
2.43.0