Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932118Ab1BCM57 (ORCPT ); Thu, 3 Feb 2011 07:57:59 -0500 Received: from casper.infradead.org ([85.118.1.10]:49917 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756368Ab1BCM5s convert rfc822-to-8bit (ORCPT ); Thu, 3 Feb 2011 07:57:48 -0500 Subject: Re: [PATCH -v8a 4/7] sched: Add yield_to(task, preempt) functionality From: Peter Zijlstra To: Rik van Riel Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Avi Kiviti , Srivatsa Vaddagiri , Mike Galbraith , Chris Wright , "Nakajima, Jun" In-Reply-To: <20110201095051.4ddb7738@annuminas.surriel.com> References: <20110201094433.72829892@annuminas.surriel.com> <20110201095051.4ddb7738@annuminas.surriel.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 03 Feb 2011 13:58:38 +0100 Message-ID: <1296737918.26581.366.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2644 Lines: 100 On Tue, 2011-02-01 at 09:50 -0500, Rik van Riel wrote: > +bool __sched yield_to(struct task_struct *p, bool preempt) > +{ > + struct task_struct *curr = current; > + struct rq *rq, *p_rq; > + unsigned long flags; > + bool yielded = 0; > + > + local_irq_save(flags); > + rq = this_rq(); > + > +again: > + p_rq = task_rq(p); > + double_rq_lock(rq, p_rq); > + while (task_rq(p) != p_rq) { > + double_rq_unlock(rq, p_rq); > + goto again; > + } > + > + if (!curr->sched_class->yield_to_task) > + goto out; > + > + if (curr->sched_class != p->sched_class) > + goto out; > + > + if (task_running(p_rq, p) || p->state) > + goto out; > + > + yielded = curr->sched_class->yield_to_task(rq, p, preempt); > + > + if (yielded) { > + schedstat_inc(rq, yld_count); > + current->sched_class->yield_task(rq); > + } > + > +out: > + double_rq_unlock(rq, p_rq); > + local_irq_restore(flags); > + > + if (yielded) > + schedule(); > + > + return yielded; > +} > +EXPORT_SYMBOL_GPL(yield_to); This also wants the below bit to successfully build on SMP=n, --- Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -1686,6 +1686,39 @@ static void double_rq_unlock(struct rq * __release(rq2->lock); } +#else /* CONFIG_SMP */ + +/* + * double_rq_lock - safely lock two runqueues + * + * Note this does not disable interrupts like task_rq_lock, + * you need to do so manually before calling. + */ +static void double_rq_lock(struct rq *rq1, struct rq *rq2) + __acquires(rq1->lock) + __acquires(rq2->lock) +{ + BUG_ON(!irqs_disabled()); + BUG_ON(rq1 != rq2); + raw_spin_lock(&rq1->lock); + __acquire(rq2->lock); /* Fake it out ;) */ +} + +/* + * double_rq_unlock - safely unlock two runqueues + * + * Note this does not restore interrupts like task_rq_unlock, + * you need to do so manually after calling. + */ +static void double_rq_unlock(struct rq *rq1, struct rq *rq2) + __releases(rq1->lock) + __releases(rq2->lock) +{ + BUG_ON(rq1 != rq2); + raw_spin_unlock(&rq1->lock); + __release(rq2->lock); +} + #endif static void calc_load_account_idle(struct rq *this_rq); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/