Messages in this thread | | | Date | Sun, 22 Jul 2012 09:49:53 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH 2/2] kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being executed |
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Hello,
On Sat, Jul 21, 2012 at 02:20:06PM -0400, Andy Walls wrote: > > + worker->current_work = work; > > spin_unlock_irq(&worker->lock); > > > > if (work) { > > __set_current_state(TASK_RUNNING); > > work->func(work); > > If the call to 'work->func(work);' frees the memory pointed to by > 'work', 'worker->current_work' points to deallocated memory. > So 'worker->current_work' will only ever used as a unique 'work' > identifier to handle, correct?
Yeah. flush_kthread_work(@work) which can only be called if @work is known to be alive looks at the pointer to determine whether it's the current work item on the worker.
> > void flush_kthread_work(struct kthread_work *work) > > { > > - int seq = work->queue_seq; > > + struct kthread_flush_work fwork = { > > + KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), > > + COMPLETION_INITIALIZER_ONSTACK(fwork.done), > > + }; > > + struct kthread_worker *worker; > > + bool noop = false; > > + > > You might want a check for 'work == NULL' here, to gracefully handle > code like the following: > > void driver_work_handler(struct kthread_work *work) > { > ... > kfree(work); > } > > struct kthread_work *driver_queue_batch(void) > { > struct kthread_work *work = NULL; > ... > while (driver_more_stuff_todo()) { > work = kzalloc(sizeof(struct kthread work), GFP_WHATEVER); > ... > queue_kthread_work(&driver_worker, work); > } > return work; > } > > void driver_foobar(void) > { > ... > flush_kthread_work(driver_queue_batch()); > ... > }
workqueue's flush_work() doesn't allow %NULL pointer. I don't want to make the behaviors deviate and don't see much point in changing workqueue's behavior at this point.
Thanks.
-- tejun
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