Messages in this thread | | | Date | Mon, 20 Apr 2015 16:42:35 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/2] sched: lockless wake-queues |
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On Sun, Apr 19, 2015 at 12:17:39PM -0700, Davidlohr Bueso wrote: > +void wake_q_add(struct wake_q_head *head, struct task_struct *task) > +{ > + struct wake_q_node *node = &task->wake_q; > + > + /* > + * Atomically grab the task, if ->wake_q is !nil already it means > + * its already queued (either by us or someone else) and will get the > + * wakeup due to that. > + * > + * This cmpxchg() implies a full barrier, which pairs with the write > + * barrier implied by the wakeup in wake_up_list(). > + */ > + if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL)) > + return; > + > + get_task_struct(task); > + > + /* > + * The head is context local, there can be no concurrency. > + */ > + if (head->first == WAKE_Q_TAIL) > + head->first = node; > + else > + head->last->next = node; > + > + head->last = node; > +}
Do we want a sched_feat() that makes the above to an immediate wake-up instead of the fancy thing? -- just for debuging/performance measurements like things?
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