From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Chris Mason <chris.mason@oracle.com>
Cc: Frank Rowand <frank.rowand@am.sony.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Mike Galbraith <efault@gmx.de>, Oleg Nesterov <oleg@redhat.com>,
Paul Turner <pjt@google.com>, Jens Axboe <axboe@kernel.dk>,
Yong Zhang <yong.zhang0@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 14/18] sched: Remove rq->lock from the first half of ttwu()
Date: Thu, 06 Jan 2011 17:29:13 +0100 [thread overview]
Message-ID: <1294331353.2016.378.camel@laptop> (raw)
In-Reply-To: <20110104150103.012710349@chello.nl>
On Tue, 2011-01-04 at 15:59 +0100, Peter Zijlstra wrote:
> Index: linux-2.6/kernel/sched_fair.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched_fair.c
> +++ linux-2.6/kernel/sched_fair.c
> @@ -1343,8 +1343,7 @@ static void task_waking_fair(struct task
> struct sched_entity *se = &p->se;
> struct cfs_rq *cfs_rq = cfs_rq_of(se);
>
> - lockdep_assert_held(&task_rq(p)->lock);
> -
> + // XXX racy on 32bit
> se->vruntime -= cfs_rq->min_vruntime;
> }
Best I can come up with is something like this:
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -315,6 +315,9 @@ struct cfs_rq {
u64 exec_clock;
u64 min_vruntime;
+#ifndef CONFIG_64BIT
+ u64 min_vruntime_copy;
+#endif
struct rb_root tasks_timeline;
struct rb_node *rb_leftmost;
Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -365,6 +365,10 @@ static void update_min_vruntime(struct c
}
cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
+#ifndef CONFIG_64BIT
+ smp_wmb();
+ cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
+#endif
}
/*
@@ -1342,9 +1346,21 @@ static void task_waking_fair(struct task
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ u64 min_vruntime;
- // XXX racy on 32bit
- se->vruntime -= cfs_rq->min_vruntime;
+#ifndef CONFIG_64BIT
+ u64 min_vruntime_copy;
+
+ do {
+ min_vruntime_copy = cfs_rq->min_vruntime_copy;
+ smp_rmb();
+ min_vruntime = cfs_rq->min_vruntime;
+ } while (min_vruntime != min_vruntime_copy);
+#else
+ min_vruntime = cfs_rq->min_vruntime;
+#endif
+
+ se->vruntime -= min_vruntime;
}
#ifdef CONFIG_FAIR_GROUP_SCHED
next prev parent reply other threads:[~2011-01-06 16:29 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-04 14:59 [RFC][PATCH 00/18] sched: Reduce runqueue lock contention -v4 Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 01/18] sched: Always provide p->on_cpu Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 02/18] mutex: Use p->on_cpu for the adaptive spin Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 03/18] sched: Change the ttwu success details Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 04/18] sched: Clean up ttwu stats Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 05/18] sched: Provide p->on_rq Peter Zijlstra
2011-01-05 8:13 ` Yong Zhang
2011-01-05 9:53 ` Peter Zijlstra
2011-01-29 0:10 ` Frank Rowand
2011-01-04 14:59 ` [RFC][PATCH 06/18] sched: Serialize p->cpus_allowed and ttwu() using p->pi_lock Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 07/18] sched: Drop the rq argument to sched_class::select_task_rq() Peter Zijlstra
2011-01-06 13:57 ` Peter Zijlstra
2011-01-06 14:23 ` Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 08/18] sched: Remove rq argument to sched_class::task_waking() Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 09/18] sched: Delay task_contributes_to_load() Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 10/18] sched: Also serialize ttwu_local() with p->pi_lock Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 11/18] sched: Add p->pi_lock to task_rq_lock() Peter Zijlstra
2011-01-05 18:46 ` Oleg Nesterov
2011-01-05 19:33 ` Peter Zijlstra
2011-01-29 0:21 ` Frank Rowand
2011-02-03 17:16 ` Peter Zijlstra
2011-02-03 17:49 ` Frank Rowand
2011-01-04 14:59 ` [RFC][PATCH 12/18] sched: Drop rq->lock from first part of wake_up_new_task() Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 13/18] sched: Drop rq->lock from sched_exec() Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 14/18] sched: Remove rq->lock from the first half of ttwu() Peter Zijlstra
2011-01-06 16:29 ` Peter Zijlstra [this message]
2011-01-29 1:05 ` Frank Rowand
2011-02-03 17:16 ` Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 15/18] sched: Remove rq argument from ttwu_stat() Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 16/18] sched: Rename ttwu_post_activation Peter Zijlstra
2011-01-29 1:08 ` Frank Rowand
2011-01-04 14:59 ` [RFC][PATCH 17/18] sched: Move the second half of ttwu() to the remote cpu Peter Zijlstra
2011-01-05 21:07 ` Oleg Nesterov
2011-01-06 15:09 ` Peter Zijlstra
2011-01-07 15:22 ` Oleg Nesterov
2011-01-18 16:38 ` Peter Zijlstra
2011-01-19 19:37 ` Oleg Nesterov
2011-01-29 0:04 ` Frank Rowand
2011-02-03 17:16 ` Peter Zijlstra
2011-01-04 14:59 ` [RFC][PATCH 18/18] sched: Sort hotplug vs ttwu queueing Peter Zijlstra
2011-01-05 20:47 ` Oleg Nesterov
2011-01-06 10:56 ` Peter Zijlstra
2011-01-04 15:16 ` [RFC][PATCH 00/18] sched: Reduce runqueue lock contention -v4 Ingo Molnar
2011-01-29 1:20 ` Frank Rowand
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