PM: wakeup: Add kfuncs to traverse over wakeup_sources

Iterating through wakeup sources via sysfs or debugfs can be inefficient
or restricted. Introduce BPF kfuncs to allow high-performance and safe
in-kernel traversal of the wakeup_sources list. There is at least a 30x
speedup for walking 150 wakeup sources and all their attributes.

The new kfuncs include:
- bpf_wakeup_sources_get_head() to obtain the list head.
- bpf_wakeup_sources_read_lock/unlock() to manage the SRCU lock.

For verifier safety, the underlying SRCU index is wrapped in an opaque
'struct bpf_ws_lock' pointer. This enables the use of KF_ACQUIRE and
KF_RELEASE flags, allowing the BPF verifier to strictly enforce paired
lock/unlock cycles and prevent resource leaks.

Signed-off-by: Samuel Wu <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://lore.kernel.org/r/20260511174559.659782-2-wusamuel@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

0 files changed, 0 insertions, 0 deletions