Messages in this thread | | | Date | Mon, 2 Aug 2021 15:10:06 +0200 | From | Peter Zijlstra <> | Subject | Re: [patch 58/63] futex: Prevent requeue_pi() lock nesting issue on RT |
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On Mon, Aug 02, 2021 at 02:56:09PM +0200, Peter Zijlstra wrote: > static inline int futex_requeue_pi_wakeup_sync(struct futex_q *q) > { > + int old, new; > > + old = atomic_read_acquire(&q->requeue_state); > + do { > /* Is requeue done already? */ > + if (old >= Q_REQUEUE_PI_DONE) > break;
I think that can be: return old; for slightly simpler code.
> > /* > * If not done, then tell the requeue code to either ignore > * the waiter or to wake it up once the requeue is done. > */ > + new = Q_REQUEUE_PI_WAIT; > + if (old == Q_REQUEUE_PI_NONE) > + new = Q_REQUEUE_PI_IGNORE; > + } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new)); > > /* If the requeue was in progress, wait for it to complete */ > + if (old == Q_REQUEUE_PI_IN_PROGRESS) { > #ifdef CONFIG_PREEMPT_RT > rcuwait_wait_event(&q->requeue_wait, > atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT, > TASK_UNINTERRUPTIBLE); > #else > + (void)atomic_cond_read_relaxed(&q->requeue_state, VAL != Q_REQUEUE_PI_WAIT); > #endif > } >
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