Messages in this thread | | | Date | Wed, 23 Feb 2022 09:57:27 +0900 | Subject | Re: [PATCH] workqueue: Use private WQ for schedule_on_each_cpu() API | From | Tetsuo Handa <> |
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On 2022/02/23 2:29, Tejun Heo wrote: > On Mon, Feb 21, 2022 at 07:38:09PM +0900, Tetsuo Handa wrote: >> Since schedule_on_each_cpu() calls schedule_work_on() and flush_work(), >> we should avoid using system_wq in order to avoid unexpected locking >> dependency. > > I don't get it. schedule_on_each_cpu() is flushing each work item and thus > shouldn't need its own flushing domain. What's this change for?
A kernel test robot tested "[PATCH v2] workqueue: Warn flush attempt using system-wide workqueues" on 5.16.0-06523-g29bd199e4e73 and hit a lockdep warning ( https://lkml.kernel.org/r/20220221083358.GC835@xsang-OptiPlex-9020 ).
Although the circular locking dependency itself needs to be handled by lockless console printing support, we won't be able to apply "[PATCH v2] workqueue: Warn flush attempt using system-wide workqueues" if schedule_on_each_cpu() continues using system-wide workqueues.
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