Re: [PATCH v5 04/20] kthread: Add drain_kthread_worker()
flat view
From: Peter Zijlstra <peterz@infradead.org>
Date: 2016-02-25 12:36:04
Also in:
linux-mm, lkml
On Mon, Feb 22, 2016 at 03:56:54PM +0100, Petr Mladek wrote:
quoted hunk ↗ jump to hunk
+/** + * drain_kthread_worker - drain a kthread worker + * @worker: worker to be drained + * + * Wait until there is no work queued for the given kthread worker. + * @worker is flushed repeatedly until it becomes empty. The number + * of flushing is determined by the depth of chaining and should + * be relatively short. Whine if it takes too long. + * + * The caller is responsible for blocking all users of this kthread + * worker from queuing new works. Also it is responsible for blocking + * the already queued works from an infinite re-queuing! + */ +void drain_kthread_worker(struct kthread_worker *worker) +{ + int flush_cnt = 0; + + spin_lock_irq(&worker->lock);
Would it not make sense to set a flag here that inhibits (or warns) queueing new work? Otherwise this can, as you point out, last forever. And I think its a logic fail if you both want to drain it and keeping adding new work.
+ while (!list_empty(&worker->work_list)) {
+ spin_unlock_irq(&worker->lock);
+
+ flush_kthread_worker(worker);
+ WARN_ONCE(flush_cnt++ > 10,
+ "kthread worker %s: drain_kthread_worker() isn't complete after %u tries\n",
+ worker->task->comm, flush_cnt);
+
+ spin_lock_irq(&worker->lock);
+ }
+
+ spin_unlock_irq(&worker->lock);
+}
+EXPORT_SYMBOL(drain_kthread_worker);
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