Messages in this thread | | | Date | Mon, 25 Jun 2007 19:20:11 +0400 | From | Oleg Nesterov <> | Subject | synchronize_qrcu_timeout() |
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On 06/25, Paul E. McKenney wrote: > > On Mon, Jun 25, 2007 at 02:43:32PM +0400, Oleg Nesterov wrote: > > > > Sadly, you can't use srcu/qrcu because it doesn't handle timeouts. > > Interesting... So the thought is to have a synchronize_srcu_timeout() > or something similar that waited for a grace period to elapse or for > a timeout to expire, whichever comes first? It should not be too hard > to arrange something, if needed.
Yes. As for qrcu (see http://marc.info/?t=116484476500001), I think it is easy. First, we add "int interrupted" into struct qrcu_struct, then something like this
long synchronize_qrcu_timeout(struct qrcu_struct *qp, long tout) { int idx;
smp_mb(); mutex_lock(&qp->mutex);
again: idx = qp->completed & 0x1;
if (unlikely(qp->interrupted)) { idx ^= 0x1; goto restart; }
if (atomic_read(qp->ctr + idx) == 1) goto out;
atomic_inc(qp->ctr + (idx ^ 0x1)); qp->completed++;
atomic_dec(qp->ctr + idx); restart: __wait_event_timeout(qp->wq, !atomic_read(qp->ctr + idx), tout); if (unlikely(!tout)) { qp->interrupted = 1; goto out; }
if (unlikely(qp->interrupted)) { qp->interrupted = 0; goto again; }
out: mutex_unlock(&qp->mutex); smp_mb();
return tout; }
Of course, this needs some other changes to implement synchronize_qrcu() on top of synchronize_qrcu_timeout(). I also think that this doesn't break
[RFC PATCH] QRCU fastpath optimization http://marc.info/?l=linux-kernel&m=117125577710947
Looks like we can do something similar for srcu.
Oleg.
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