Merge branch 'support-bpf-traversal-of-wakeup-sources'

Samuel Wu says:

====================
Support BPF traversal of wakeup sources

This patchset adds requisite kfuncs for BPF programs to safely traverse
wakeup_sources, and puts a config flag around the sysfs interface.

Currently, a traversal of wakeup sources require going through
/sys/class/wakeup/* or /d/wakeup_sources/*. The repeated syscalls to query
sysfs is inefficient, as there can be hundreds of wakeup_sources, with each
wakeup source also having multiple attributes. debugfs is unstable and
insecure.

Adding kfuncs to lock/unlock wakeup sources allows BPF program to safely
traverse the wakeup sources list, and a kfunc to get head of wakeup
sources list is needed to start traversing the list.

On a quiescent Pixel 6 traversing 150 wakeup_sources, I am seeing ~34x
speedup (sampled 75 times in table below). For a device under load, the
speedup is greater.
+-------+----+----------+----------+
|       | n  | AVG (ms) | STD (ms) |
+-------+----+----------+----------+
| sysfs | 75 | 44.9     | 12.6     |
+-------+----+----------+----------+
| BPF   | 75 | 1.3      | 0.7      |
+-------+----+----------+----------+

The initial attempts for BPF traversal of wakeup_sources was with BPF
iterators [1]. However, BPF already allows for traversing of a simple list
with bpf_for(), and this current patchset has the added benefit of being
~2-3x more performant than BPF iterators.

[1]: https://lore.kernel.org/all/20260225210820.177674-1-wusamuel@google.com/

Changes in v4:
- Removed `.owner = THIS_MODULE` for btf_kfunc_id_set per Greg
- Add a graceful exit in selftest if bpf_wakeup_sources_get_head() is not
  present due to kernel configs without CONFIG_PM_SLEEP (e.g. s390)
- Relaxed substr match in wakeup_source_unlock_null() selftest
link: https://lore.kernel.org/all/20260331153413.2469218-1-wusamuel@google.com/
Changes in v3:
- Changed return type of bpf_wakeup_sources_get_head() to `void *` per Alexei
- Added failure test for direct dereference of wakeup source head
- Use bpf_core_cast() instead of macros in BPF program per Kumar
link: https://lore.kernel.org/all/20260326112521.2827500-1-wusamuel@google.com/
Changes in v2:
- Dropped CONFIG_PM_WAKEUP_STATS_SYSFS patch for future patchset
- Added declarations for kfuncs to .h to fix sparse and checkpatch warnings
- Added kfunc to get address of wakeup_source's head
- Added example bpf prog selftest for traversal of wakeup sources per Kumar
- Added *_fail.c selftest per Kumar
- More concise commit message in patch 1/2
link: https://lore.kernel.org/all/20260320160055.4114055-1-wusamuel@google.com/
====================

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/20260511174559.659782-1-wusamuel@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>