Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-09-20 15:03:04 +00:00
Code Issues Packages Projects Releases Wiki Activity

workqueue: Fix WARN_ON_ONCE() triggers in worker_enter_idle()

Browse Source 
Currently, pool->nr_running can be modified from timer tick, that means the
timer tick can run nested inside a not-irq-protected section that's in the
process of modifying nr_running. 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()
         ->worker->sleeping = 1;
         ->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->sleeping = 0;
         ....
    ->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 the check of worker->sleeping in wq_worker_tick(),
if the worker->sleeping is not zero, directly return.

tj: Updated comment and description.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Anders Roxell <anders.roxell@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>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Zqiang 2023-05-24 11:53:39 +08:00 committed by Tejun Heo
parent 525ff9c296
commit c8f6219be2
1 changed files with 12 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
kernel/workqueue.c
View File

@ -1051,7 +1051,7 @@ void wq_worker_running(struct task_struct *task)
{
struct worker *worker = kthread_data(task);
if (!worker->sleeping)
if (!READ_ONCE(worker->sleeping))
return;
/*
@ -1071,7 +1071,7 @@ void wq_worker_running(struct task_struct *task)
*/
worker->current_at = worker->task->se.sum_exec_runtime;
worker->sleeping = 0;
WRITE_ONCE(worker->sleeping, 0);
}
/**
@ -1097,10 +1097,10 @@ void wq_worker_sleeping(struct task_struct *task)
pool = worker->pool;
/* Return if preempted before wq_worker_running() was reached */
if (worker->sleeping)
if (READ_ONCE(worker->sleeping))
return;
worker->sleeping = 1;
WRITE_ONCE(worker->sleeping, 1);
raw_spin_lock_irq(&pool->lock);
/*
@ -1143,8 +1143,15 @@ void wq_worker_tick(struct task_struct *task)
* If the current worker is concurrency managed and hogged the CPU for
* longer than wq_cpu_intensive_thresh_us, it's automatically marked
* CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
*
* Set @worker->sleeping means that @worker is in the process of
* switching out voluntarily and won't be contributing to
* @pool->nr_running until it wakes up. As wq_worker_sleeping() also
* decrements ->nr_running, setting CPU_INTENSIVE here can lead to
* double decrements. The task is releasing the CPU anyway. Let's skip.
* We probably want to make this prettier in the future.
*/
if ((worker->flags & WORKER_NOT_RUNNING) ||
if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
worker->task->se.sum_exec_runtime - worker->current_at <
wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
return;