Messages in this thread | | | Date | Mon, 27 Jun 2016 16:33:50 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH v9 06/12] kthread: Add kthread_drain_worker() |
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Hi,
On Fri 2016-06-24 11:54:47, Tejun Heo wrote: > On Fri, Jun 24, 2016 at 09:05:15AM +0200, Peter Zijlstra wrote: > > > Given how rare that is > > > > Could you then not remove/rework these few cases for workqueue as well > > and make that 'better' too? > > Usage of draining is rare for workqueue but that still means several > legitimate users. With draining there, it's logical to use it during > shutdown. I don't think it makes sense to change it on workqueue > side. > > > > and the extra > > > complexity of identifying self-requeueing cases, let's forget about > > > draining and on destruction clear the worker pointer to block further > > > queueing and then flush whatever is in flight. > > > > You're talking about regular workqueues here? > > No, kthread worker. It's unlikely that kthread worker is gonna need > chained draining especially given that most of its usages are gonna be > conversions from raw kthread usages. We won't lose much if anything > by just ignoring draining and making the code simpler.
OK, so you suggest to do the following:
1. Add a flag into struct kthread_worker that will prevent from further queuing.
2. kthread_create_worker()/kthread_destroy_worker() will not longer dynamically allocate struct kthread_worker. They will just start/stop the kthread.
The result will be:
a. User will not need the strict synchronization between the queue and create/destroy operations.
b. We could get rid of drain_kthread_worker() because flush_kthread_worker() will be enough.
IMHO, the 1st change does not make sense without the 2nd one. Otherwise, users could do an out-of-memory access when testing the freed kthread_worker flag.
Do I get this correctly please?
Best Regards, Petr
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