From: tip-bot for Peter Zijlstra <a.p.zijlstra@chello.nl>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com,
torvalds@linux-foundation.org, a.p.zijlstra@chello.nl,
efault@gmx.de, npiggin@kernel.dk, akpm@linux-foundation.org,
tglx@linutronix.de, frank.rowand@am.sony.com, mingo@elte.hu
Subject: [tip:sched/locking] sched: Drop the rq argument to sched_class::select_task_rq()
Date: Thu, 14 Apr 2011 08:34:40 GMT [thread overview]
Message-ID: <tip-7608dec2ce2004c234339bef8c8074e5e601d0e9@git.kernel.org> (raw)
In-Reply-To: <20110405152729.031077745@chello.nl>
Commit-ID: 7608dec2ce2004c234339bef8c8074e5e601d0e9
Gitweb: http://git.kernel.org/tip/7608dec2ce2004c234339bef8c8074e5e601d0e9
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 5 Apr 2011 17:23:46 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 14 Apr 2011 08:52:36 +0200
sched: Drop the rq argument to sched_class::select_task_rq()
In preparation of calling select_task_rq() without rq->lock held, drop
the dependency on the rq argument.
Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110405152729.031077745@chello.nl
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/linux/sched.h | 3 +--
kernel/sched.c | 20 +++++++++++---------
kernel/sched_fair.c | 2 +-
kernel/sched_idletask.c | 2 +-
kernel/sched_rt.c | 38 ++++++++++++++++++++++++++------------
kernel/sched_stoptask.c | 3 +--
6 files changed, 41 insertions(+), 27 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b33a700..ff4e2f9 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1067,8 +1067,7 @@ struct sched_class {
void (*put_prev_task) (struct rq *rq, struct task_struct *p);
#ifdef CONFIG_SMP
- int (*select_task_rq)(struct rq *rq, struct task_struct *p,
- int sd_flag, int flags);
+ int (*select_task_rq)(struct task_struct *p, int sd_flag, int flags);
void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);
void (*post_schedule) (struct rq *this_rq);
diff --git a/kernel/sched.c b/kernel/sched.c
index d398f2f..d4b815d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2195,13 +2195,15 @@ static int migration_cpu_stop(void *data);
* The task's runqueue lock must be held.
* Returns true if you have to wait for migration thread.
*/
-static bool migrate_task(struct task_struct *p, struct rq *rq)
+static bool need_migrate_task(struct task_struct *p)
{
/*
* If the task is not on a runqueue (and not running), then
* the next wake-up will properly place the task.
*/
- return p->on_rq || task_running(rq, p);
+ bool running = p->on_rq || p->on_cpu;
+ smp_rmb(); /* finish_lock_switch() */
+ return running;
}
/*
@@ -2376,9 +2378,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
* The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
*/
static inline
-int select_task_rq(struct rq *rq, struct task_struct *p, int sd_flags, int wake_flags)
+int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags)
{
- int cpu = p->sched_class->select_task_rq(rq, p, sd_flags, wake_flags);
+ int cpu = p->sched_class->select_task_rq(p, sd_flags, wake_flags);
/*
* In order not to call set_task_cpu() on a blocking task we need
@@ -2533,7 +2535,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
en_flags |= ENQUEUE_WAKING;
}
- cpu = select_task_rq(rq, p, SD_BALANCE_WAKE, wake_flags);
+ cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);
if (cpu != orig_cpu)
set_task_cpu(p, cpu);
__task_rq_unlock(rq);
@@ -2744,7 +2746,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
* We set TASK_WAKING so that select_task_rq() can drop rq->lock
* without people poking at ->cpus_allowed.
*/
- cpu = select_task_rq(rq, p, SD_BALANCE_FORK, 0);
+ cpu = select_task_rq(p, SD_BALANCE_FORK, 0);
set_task_cpu(p, cpu);
p->state = TASK_RUNNING;
@@ -3474,7 +3476,7 @@ void sched_exec(void)
int dest_cpu;
rq = task_rq_lock(p, &flags);
- dest_cpu = p->sched_class->select_task_rq(rq, p, SD_BALANCE_EXEC, 0);
+ dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);
if (dest_cpu == smp_processor_id())
goto unlock;
@@ -3482,7 +3484,7 @@ void sched_exec(void)
* select_task_rq() can race against ->cpus_allowed
*/
if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed) &&
- likely(cpu_active(dest_cpu)) && migrate_task(p, rq)) {
+ likely(cpu_active(dest_cpu)) && need_migrate_task(p)) {
struct migration_arg arg = { p, dest_cpu };
task_rq_unlock(rq, &flags);
@@ -5911,7 +5913,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
goto out;
dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
- if (migrate_task(p, rq)) {
+ if (need_migrate_task(p)) {
struct migration_arg arg = { p, dest_cpu };
/* Need help from migration thread: drop lock and wait. */
__task_rq_unlock(rq);
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 4ee50f0..96b2c95 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1657,7 +1657,7 @@ static int select_idle_sibling(struct task_struct *p, int target)
* preempt must be disabled.
*/
static int
-select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)
+select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
{
struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
int cpu = smp_processor_id();
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index a776a63..0a51882 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -7,7 +7,7 @@
#ifdef CONFIG_SMP
static int
-select_task_rq_idle(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
+select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)
{
return task_cpu(p); /* IDLE tasks as never migrated */
}
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 9ca4f5f..19ecb31 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -977,13 +977,23 @@ static void yield_task_rt(struct rq *rq)
static int find_lowest_rq(struct task_struct *task);
static int
-select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
+select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
{
+ struct task_struct *curr;
+ struct rq *rq;
+ int cpu;
+
if (sd_flag != SD_BALANCE_WAKE)
return smp_processor_id();
+ cpu = task_cpu(p);
+ rq = cpu_rq(cpu);
+
+ rcu_read_lock();
+ curr = ACCESS_ONCE(rq->curr); /* unlocked access */
+
/*
- * If the current task is an RT task, then
+ * If the current task on @p's runqueue is an RT task, then
* try to see if we can wake this RT task up on another
* runqueue. Otherwise simply start this RT task
* on its current runqueue.
@@ -997,21 +1007,25 @@ select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
* lock?
*
* For equal prio tasks, we just let the scheduler sort it out.
+ *
+ * Otherwise, just let it ride on the affined RQ and the
+ * post-schedule router will push the preempted task away
+ *
+ * This test is optimistic, if we get it wrong the load-balancer
+ * will have to sort it out.
*/
- if (unlikely(rt_task(rq->curr)) &&
- (rq->curr->rt.nr_cpus_allowed < 2 ||
- rq->curr->prio < p->prio) &&
+ if (curr && unlikely(rt_task(curr)) &&
+ (curr->rt.nr_cpus_allowed < 2 ||
+ curr->prio < p->prio) &&
(p->rt.nr_cpus_allowed > 1)) {
- int cpu = find_lowest_rq(p);
+ int target = find_lowest_rq(p);
- return (cpu == -1) ? task_cpu(p) : cpu;
+ if (target != -1)
+ cpu = target;
}
+ rcu_read_unlock();
- /*
- * Otherwise, just let it ride on the affined RQ and the
- * post-schedule router will push the preempted task away
- */
- return task_cpu(p);
+ return cpu;
}
static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c
index f607de4..6f43763 100644
--- a/kernel/sched_stoptask.c
+++ b/kernel/sched_stoptask.c
@@ -9,8 +9,7 @@
#ifdef CONFIG_SMP
static int
-select_task_rq_stop(struct rq *rq, struct task_struct *p,
- int sd_flag, int flags)
+select_task_rq_stop(struct task_struct *p, int sd_flag, int flags)
{
return task_cpu(p); /* stop tasks as never migrate */
}
next prev parent reply other threads:[~2011-04-14 8:35 UTC|newest]
Thread overview: 152+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-05 15:23 [PATCH 00/21] sched: Reduce runqueue lock contention -v6 Peter Zijlstra
2011-04-05 15:23 ` [PATCH 01/21] sched: Provide scheduler_ipi() callback in response to smp_send_reschedule() Peter Zijlstra
2011-04-13 21:15 ` Tony Luck
2011-04-13 21:38 ` Peter Zijlstra
2011-04-14 8:31 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 02/21] sched: Always provide p->on_cpu Peter Zijlstra
2011-04-14 8:31 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 03/21] mutex: Use p->on_cpu for the adaptive spin Peter Zijlstra
2011-04-14 8:32 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 04/21] sched: Change the ttwu success details Peter Zijlstra
2011-04-13 9:23 ` Peter Zijlstra
2011-04-13 10:48 ` Peter Zijlstra
2011-04-13 11:06 ` Peter Zijlstra
2011-04-13 18:39 ` Tejun Heo
2011-04-13 19:11 ` Peter Zijlstra
2011-04-14 8:32 ` [tip:sched/locking] sched: Change the ttwu() " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 05/21] sched: Clean up ttwu stats Peter Zijlstra
2011-04-14 8:33 ` [tip:sched/locking] sched: Clean up ttwu() stats tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 06/21] sched: Provide p->on_rq Peter Zijlstra
2011-04-14 8:33 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 07/21] sched: Serialize p->cpus_allowed and ttwu() using p->pi_lock Peter Zijlstra
2011-04-14 8:34 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 08/21] sched: Drop the rq argument to sched_class::select_task_rq() Peter Zijlstra
2011-04-14 8:34 ` tip-bot for Peter Zijlstra [this message]
2011-04-05 15:23 ` [PATCH 09/21] sched: Remove rq argument to sched_class::task_waking() Peter Zijlstra
2011-04-14 8:35 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 10/21] sched: Deal with non-atomic min_vruntime reads on 32bits Peter Zijlstra
2011-04-14 8:35 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 11/21] sched: Delay task_contributes_to_load() Peter Zijlstra
2011-04-14 8:35 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 12/21] sched: Also serialize ttwu_local() with p->pi_lock Peter Zijlstra
2011-04-14 8:36 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 13/21] sched: Add p->pi_lock to task_rq_lock() Peter Zijlstra
2011-04-14 8:36 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-06-01 13:58 ` Arne Jansen
2011-06-01 16:35 ` Peter Zijlstra
2011-06-01 17:20 ` Arne Jansen
2011-06-01 18:09 ` Peter Zijlstra
2011-06-01 18:44 ` Peter Zijlstra
2011-06-01 19:30 ` Arne Jansen
2011-06-01 21:09 ` Linus Torvalds
2011-06-03 9:15 ` Peter Zijlstra
2011-06-03 10:02 ` Arne Jansen
2011-06-03 10:30 ` Peter Zijlstra
2011-06-03 11:52 ` Arne Jansen
2011-06-05 8:17 ` Ingo Molnar
2011-06-05 8:53 ` Arne Jansen
2011-06-05 9:41 ` Ingo Molnar
2011-06-05 9:45 ` Ingo Molnar
2011-06-05 9:43 ` Arne Jansen
2011-06-05 9:55 ` Ingo Molnar
2011-06-05 10:22 ` Arne Jansen
2011-06-05 11:01 ` Ingo Molnar
2011-06-05 11:19 ` [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages Ingo Molnar
2011-06-05 11:36 ` Ingo Molnar
2011-06-05 11:57 ` Arne Jansen
2011-06-05 13:39 ` Ingo Molnar
2011-06-05 13:54 ` Arne Jansen
2011-06-05 14:06 ` Ingo Molnar
2011-06-05 14:45 ` Arne Jansen
2011-06-05 14:10 ` Ingo Molnar
2011-06-05 14:31 ` Arne Jansen
2011-06-05 15:13 ` Ingo Molnar
2011-06-05 15:26 ` Ingo Molnar
2011-06-05 15:32 ` Ingo Molnar
2011-06-05 16:07 ` Arne Jansen
2011-06-05 16:35 ` Arne Jansen
2011-06-05 16:50 ` Arne Jansen
2011-06-05 17:20 ` Ingo Molnar
2011-06-05 17:42 ` Arne Jansen
2011-06-05 18:59 ` Ingo Molnar
2011-06-05 19:30 ` Arne Jansen
2011-06-05 19:44 ` Ingo Molnar
2011-06-05 20:15 ` Arne Jansen
2011-06-06 6:56 ` Arne Jansen
2011-06-06 9:01 ` Peter Zijlstra
2011-06-06 9:18 ` Arne Jansen
2011-06-06 9:24 ` Peter Zijlstra
2011-06-06 9:52 ` Peter Zijlstra
2011-06-06 10:00 ` Arne Jansen
2011-06-06 10:26 ` Peter Zijlstra
2011-06-06 13:25 ` Peter Zijlstra
2011-06-06 15:04 ` Ingo Molnar
2011-06-06 15:08 ` Ingo Molnar
2011-06-06 17:44 ` Mike Galbraith
2011-06-07 5:20 ` Mike Galbraith
2011-06-06 13:10 ` Ingo Molnar
2011-06-06 13:12 ` Peter Zijlstra
2011-06-06 13:21 ` Ingo Molnar
2011-06-06 13:31 ` Peter Zijlstra
2011-06-06 7:34 ` Arne Jansen
2011-06-05 15:34 ` Arne Jansen
2011-06-06 8:38 ` Peter Zijlstra
2011-06-06 14:58 ` Ingo Molnar
2011-06-06 15:09 ` Peter Zijlstra
2011-06-06 15:47 ` Peter Zijlstra
2011-06-06 15:52 ` Ingo Molnar
2011-06-06 16:00 ` Peter Zijlstra
2011-06-06 16:08 ` Ingo Molnar
2011-06-06 16:12 ` Peter Zijlstra
2011-06-06 16:17 ` Ingo Molnar
2011-06-06 16:38 ` Arne Jansen
2011-06-06 16:45 ` Arne Jansen
2011-06-06 16:53 ` Peter Zijlstra
2011-06-06 17:07 ` Ingo Molnar
2011-06-06 17:11 ` Peter Zijlstra
2011-06-08 15:50 ` Peter Zijlstra
2011-06-08 19:17 ` Ingo Molnar
2011-06-08 19:27 ` Linus Torvalds
2011-06-08 20:32 ` Peter Zijlstra
2011-06-08 20:53 ` Linus Torvalds
2011-06-08 20:54 ` Thomas Gleixner
2011-06-08 19:45 ` Peter Zijlstra
2011-06-08 20:52 ` Ingo Molnar
2011-06-08 21:49 ` Peter Zijlstra
2011-06-08 21:57 ` Thomas Gleixner
2011-06-06 16:44 ` Peter Zijlstra
2011-06-06 16:50 ` Peter Zijlstra
2011-06-06 17:13 ` Ingo Molnar
2011-06-06 17:04 ` Peter Zijlstra
2011-06-06 17:11 ` Ingo Molnar
2011-06-06 17:57 ` Arne Jansen
2011-06-06 18:07 ` Ingo Molnar
2011-06-06 18:14 ` Arne Jansen
2011-06-06 18:19 ` Peter Zijlstra
2011-06-06 22:08 ` Ingo Molnar
2011-06-03 12:44 ` [tip:sched/locking] sched: Add p->pi_lock to task_rq_lock() Linus Torvalds
2011-06-03 13:05 ` Arne Jansen
2011-06-04 21:29 ` Linus Torvalds
2011-06-04 22:08 ` Peter Zijlstra
2011-06-04 22:50 ` Linus Torvalds
2011-06-05 6:01 ` Arne Jansen
2011-06-05 7:57 ` Mike Galbraith
2011-04-05 15:23 ` [PATCH 14/21] sched: Drop rq->lock from first part of wake_up_new_task() Peter Zijlstra
2011-04-14 8:37 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 15/21] sched: Drop rq->lock from sched_exec() Peter Zijlstra
2011-04-14 8:37 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 16/21] sched: Remove rq->lock from the first half of ttwu() Peter Zijlstra
2011-04-14 8:38 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 17/21] sched: Remove rq argument from ttwu_stat() Peter Zijlstra
2011-04-14 8:38 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 18/21] sched: Rename ttwu_post_activation Peter Zijlstra
2011-04-14 8:39 ` [tip:sched/locking] sched: Rename ttwu_post_activation() to ttwu_do_wakeup() tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 19/21] sched: Restructure ttwu some more Peter Zijlstra
2011-04-14 8:39 ` [tip:sched/locking] sched: Restructure ttwu() " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 20/21] sched: Move the second half of ttwu() to the remote cpu Peter Zijlstra
2011-04-14 8:39 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 21/21] sched: Remove need_migrate_task() Peter Zijlstra
2011-04-14 8:40 ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:59 ` [PATCH 00/21] sched: Reduce runqueue lock contention -v6 Peter Zijlstra
2011-04-06 11:00 ` Peter Zijlstra
2011-04-27 16:54 ` Dave Kleikamp
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