diff options
| author | Breno Leitao <leitao@debian.org> | 2026-07-03 08:52:50 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-07-06 11:22:32 -1000 |
| commit | 5eaadebf10e77b190f01ecb211c110c69275b7bd (patch) | |
| tree | 40afa389218f5c9e7644a8f8ae2b764ed1823d21 /kernel | |
| parent | ecf5aad9a4417fece80890f27a9899db90c9c457 (diff) | |
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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index f8b5598f7272..4ec3db31493d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1468,7 +1468,7 @@ void wq_worker_running(struct task_struct *task) * CPU intensive auto-detection cares about how long a work item hogged * CPU without sleeping. Reset the starting timestamp on wakeup. */ - worker->current_at = worker->task->se.sum_exec_runtime; + worker->current_at = READ_ONCE(worker->task->se.sum_exec_runtime); WRITE_ONCE(worker->sleeping, 0); } @@ -1557,7 +1557,7 @@ void wq_worker_tick(struct task_struct *task) * We probably want to make this prettier in the future. */ if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) || - worker->task->se.sum_exec_runtime - worker->current_at < + READ_ONCE(worker->task->se.sum_exec_runtime) - worker->current_at < wq_cpu_intensive_thresh_us * NSEC_PER_USEC) return; @@ -3294,7 +3294,7 @@ __acquires(&pool->lock) worker->current_func = work->func; worker->current_pwq = pwq; if (worker->task) - worker->current_at = worker->task->se.sum_exec_runtime; + worker->current_at = READ_ONCE(worker->task->se.sum_exec_runtime); worker->current_start = jiffies; work_data = *work_data_bits(work); worker->current_color = get_work_color(work_data); |