workqueue: Add workqueue_cpu_intensive tracepoint

When a concurrency-managed per-CPU work item runs continuously without
sleeping for longer than wq_cpu_intensive_thresh_us, wq_worker_tick() marks
the worker as WORKER_CPU_INTENSIVE and kicks it out of concurrency
management so that pending work items on the pool are not starved.

While CONFIG_WQ_CPU_INTENSIVE_REPORT logs rate-limited warnings and
pwq->stats[PWQ_STAT_CPU_INTENSIVE] maintains a cumulative counter, there is
currently no tracepoint emitted at the moment of this transition.

Therefore, add the workqueue_cpu_intensive tracepoint, recording the
work_struct pointer and callback function pointer, workqueue name,
executing CPU, and the runtime duration consumed in microseconds.

This enables eBPF profilers, bpftrace, and Ftrace to immediately detect and
attribute CPU-hogging work items in real time.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions