Messages in this thread Patch in this message | | | From | Zqiang <> | Subject | [PATCH] workqueue: Fix warning triggered when nr_running is checked in worker_enter_idle() | Date | Tue, 23 May 2023 11:19:33 +0800 |
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Currently, the nr_running can be modified from timer tick, that means the timer tick can run in not-irq-protected critical section to modify nr_runnig, consider the following scenario:
CPU0 kworker/0:2 (events) worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND); ->pool->nr_running++; (1)
process_one_work() ->worker->current_func(work); ->schedule() ->wq_worker_sleeping() ->pool->nr_running--; (0) .... ->wq_worker_running() .... CPU0 by interrupt: wq_worker_tick() ->worker_set_flags(worker, WORKER_CPU_INTENSIVE); ->pool->nr_running--; (-1) ->worker->flags |= WORKER_CPU_INTENSIVE; .... ->if (!(worker->flags & WORKER_NOT_RUNNING)) ->pool->nr_running++; (will not execute) .... ->worker_clr_flags(worker, WORKER_CPU_INTENSIVE); ->pool->nr_running++; (0) .... worker_set_flags(worker, WORKER_PREP); ->pool->nr_running--; (-1) .... worker_enter_idle() ->WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
if the nr_workers is equal to nr_idle, due to the nr_running is not zero, will trigger WARN_ON_ONCE().
[ 2.460602] WARNING: CPU: 0 PID: 63 at kernel/workqueue.c:1999 worker_enter_idle+0xb2/0xc0 [ 2.462163] Modules linked in: [ 2.463401] CPU: 0 PID: 63 Comm: kworker/0:2 Not tainted 6.4.0-rc2-next-20230519 #1 [ 2.463771] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 [ 2.465127] Workqueue: 0x0 (events) [ 2.465678] RIP: 0010:worker_enter_idle+0xb2/0xc0 ... [ 2.472614] Call Trace: [ 2.473152] <TASK> [ 2.474182] worker_thread+0x71/0x430 [ 2.474992] ? _raw_spin_unlock_irqrestore+0x28/0x50 [ 2.475263] kthread+0x103/0x120 [ 2.475493] ? __pfx_worker_thread+0x10/0x10 [ 2.476355] ? __pfx_kthread+0x10/0x10 [ 2.476635] ret_from_fork+0x2c/0x50 [ 2.477051] </TASK>
This commit therefore add irq protection in wq_worker_running() to block timer tick modify nr_running.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Closes: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20230519/testrun/17078554/suite/boot/test/clang-nightly-lkftconfig/log Signed-off-by: Zqiang <qiang.zhang1211@gmail.com> --- kernel/workqueue.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 9c5c1cfa478f..f8d739fef311 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1060,10 +1060,9 @@ void wq_worker_running(struct task_struct *task) * and leave with an unexpected pool->nr_running == 1 on the newly unbound * pool. Protect against such race. */ - preempt_disable(); + local_irq_disable(); if (!(worker->flags & WORKER_NOT_RUNNING)) worker->pool->nr_running++; - preempt_enable(); /* * CPU intensive auto-detection cares about how long a work item hogged @@ -1072,6 +1071,7 @@ void wq_worker_running(struct task_struct *task) worker->current_at = worker->task->se.sum_exec_runtime; worker->sleeping = 0; + local_irq_enable(); } /** -- 2.17.1
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