workqueue: annotate racy sum_exec_runtime reads for CPU-intensive detection

The automatic CPU-intensive work item detection reads the worker task's
se.sum_exec_runtime without a lock in wq_worker_running(),
wq_worker_tick() and process_one_work(). The scheduler updates that
field under the rq lock (from the tick via update_curr(), or cross-CPU
via task_sched_runtime()), raising:

  BUG: KCSAN: data-race in wq_worker_running+0xa8/0xe8

  race at unknown origin, with read to 0xffff0009a11d1df8 of 8 bytes by task 238535 on cpu 68:
   wq_worker_running
   schedule
   schedule_preempt_disabled
   __mutex_lock
   mutex_lock_nested
   cgroup_bpf_release
   process_one_work
   worker_thread
   kthread
   ret_from_fork

  value changed: 0x0000000088482ba0 -> 0x00000000884893c0

The value only feeds a heuristic, so the race is benign-ish. Unlike
commit ecf5aad9a441 ("workqueue: annotate racy PWQ_STAT_CPU_TIME update
in wq_worker_tick()") that only needs data_race(), these are plain reads
whose result drives a subtraction and comparison, so use READ_ONCE() for
a single, non-torn load, which also silences KCSAN.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions