From: "Michael S. Tsirkin" <mst@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
Sridhar Samudrala <sri@us.ibm.com>,
netdev <netdev@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Dmitri Vorobiev <dmitri.vorobiev@movial.com>,
Jiri Kosina <jkosina@suse.cz>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH UPDATED 1/3] vhost: replace vhost_workqueue with per-vhost kthread
Date: Mon, 26 Jul 2010 19:57:24 +0300 [thread overview]
Message-ID: <20100726165724.GB27353@redhat.com> (raw)
In-Reply-To: <4C4DB466.6000409@kernel.org>
Here's an untested patch forward-ported from vhost
(works fine for vhost).
kthread_worker: replace barriers+atomics with a lock
We can save some cycles and make code simpler by
reusing worker lock for flush, instead of atomics.
flush_kthread_work needs to get worker pointer for
this to work.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 685ea65..19ae9f2 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -58,7 +58,7 @@ struct kthread_work {
struct list_head node;
kthread_work_func_t func;
wait_queue_head_t done;
- atomic_t flushing;
+ int flushing;
int queue_seq;
int done_seq;
};
@@ -72,7 +72,7 @@ struct kthread_work {
.node = LIST_HEAD_INIT((work).node), \
.func = (fn), \
.done = __WAIT_QUEUE_HEAD_INITIALIZER((work).done), \
- .flushing = ATOMIC_INIT(0), \
+ .flushing = 0, \
}
#define DEFINE_KTHREAD_WORKER(worker) \
@@ -96,7 +96,8 @@ int kthread_worker_fn(void *worker_ptr);
bool queue_kthread_work(struct kthread_worker *worker,
struct kthread_work *work);
-void flush_kthread_work(struct kthread_work *work);
+void flush_kthread_work(struct kthread_worker *worker,
+ struct kthread_work *work);
void flush_kthread_worker(struct kthread_worker *worker);
#endif /* _LINUX_KTHREAD_H */
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 2dc3786..461f58d 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -283,10 +283,12 @@ int kthreadd(void *unused)
int kthread_worker_fn(void *worker_ptr)
{
struct kthread_worker *worker = worker_ptr;
- struct kthread_work *work;
+ struct kthread_work *work = NULL;
+ spin_lock_irq(&worker->lock);
WARN_ON(worker->task);
worker->task = current;
+ spin_unlock_irq(&worker->lock);
repeat:
set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
@@ -298,23 +300,23 @@ repeat:
return 0;
}
- work = NULL;
spin_lock_irq(&worker->lock);
+ if (work) {
+ work->done_seq = work->queue_seq;
+ if (work->flushing)
+ wake_up_all(&work->done);
+ }
if (!list_empty(&worker->work_list)) {
work = list_first_entry(&worker->work_list,
struct kthread_work, node);
list_del_init(&work->node);
- }
+ } else
+ work = NULL;
spin_unlock_irq(&worker->lock);
if (work) {
__set_current_state(TASK_RUNNING);
work->func(work);
- smp_wmb(); /* wmb worker-b0 paired with flush-b1 */
- work->done_seq = work->queue_seq;
- smp_mb(); /* mb worker-b1 paired with flush-b0 */
- if (atomic_read(&work->flushing))
- wake_up_all(&work->done);
} else if (!freezing(current))
schedule();
@@ -353,31 +355,33 @@ EXPORT_SYMBOL_GPL(queue_kthread_work);
/**
* flush_kthread_work - flush a kthread_work
+ * @worker: where work might be running
* @work: work to flush
*
* If @work is queued or executing, wait for it to finish execution.
*/
-void flush_kthread_work(struct kthread_work *work)
+void flush_kthread_work(struct kthread_worker *worker,
+ struct kthread_work *work)
{
- int seq = work->queue_seq;
+ int seq
- atomic_inc(&work->flushing);
-
- /*
- * mb flush-b0 paired with worker-b1, to make sure either
- * worker sees the above increment or we see done_seq update.
- */
- smp_mb__after_atomic_inc();
+ spin_lock_irq(&worker->lock);
+ seq = work->queue_seq;
+ ++work->flushing;
+ spin_unlock_irq(&worker->lock);
/* A - B <= 0 tests whether B is in front of A regardless of overflow */
- wait_event(work->done, seq - work->done_seq <= 0);
- atomic_dec(&work->flushing);
-
- /*
- * rmb flush-b1 paired with worker-b0, to make sure our caller
- * sees every change made by work->func().
- */
- smp_mb__after_atomic_dec();
+ wait_event(work->done,
+ ({
+ int done;
+ spin_lock_irq(&worker->lock);
+ delta = seq - work->done_seq <= 0;
+ spin_unlock_irq(&worker->lock);
+ done;
+ });
+ spin_lock_irq(&worker->lock);
+ --work->flushing;
+ spin_unlock_irq(&worker->lock);
}
EXPORT_SYMBOL_GPL(flush_kthread_work);
next prev parent reply other threads:[~2010-07-26 17:03 UTC|newest]
Thread overview: 115+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-19 0:04 [PATCH 2/3] workqueue: Add an API to create a singlethread workqueue attached to the current task's cgroup Sridhar Samudrala
2010-05-27 9:14 ` Michael S. Tsirkin
2010-05-27 12:44 ` Oleg Nesterov
2010-05-27 13:12 ` Michael S. Tsirkin
2010-05-27 13:48 ` Oleg Nesterov
2010-05-27 16:15 ` Tejun Heo
2010-05-27 16:39 ` Michael S. Tsirkin
2010-05-27 16:56 ` Tejun Heo
2010-05-27 17:32 ` Michael S. Tsirkin
2010-05-27 21:20 ` Tejun Heo
2010-05-28 15:08 ` Michael S. Tsirkin
2010-05-28 15:54 ` Tejun Heo
2010-05-30 11:29 ` Michael S. Tsirkin
2010-05-30 20:24 ` [PATCH 1/3] vhost: replace vhost_workqueue with per-vhost kthread Tejun Heo
2010-05-31 14:39 ` Oleg Nesterov
2010-05-31 15:07 ` Tejun Heo
2010-05-31 15:31 ` Oleg Nesterov
2010-05-31 15:38 ` Tejun Heo
2010-05-31 15:22 ` Michael S. Tsirkin
2010-05-31 15:45 ` Tejun Heo
2010-05-31 16:00 ` Michael S. Tsirkin
2010-06-01 9:34 ` Tejun Heo
2010-06-02 18:40 ` [PATCH UPDATED " Tejun Heo
2010-06-02 21:34 ` Sridhar Samudrala
2010-07-22 15:58 ` Michael S. Tsirkin
2010-07-22 21:21 ` Tejun Heo
2010-07-24 19:14 ` Michael S. Tsirkin
2010-07-25 7:41 ` Tejun Heo
2010-07-25 10:04 ` Michael S. Tsirkin
2010-07-26 15:25 ` Michael S. Tsirkin
2010-07-26 15:34 ` Tejun Heo
2010-07-26 15:46 ` Tejun Heo
2010-07-26 15:51 ` Michael S. Tsirkin
2010-07-26 15:50 ` Michael S. Tsirkin
2010-07-26 16:05 ` Tejun Heo
2010-07-26 16:14 ` Tejun Heo
2010-07-26 16:31 ` Michael S. Tsirkin
2010-07-26 18:51 ` Tejun Heo
2010-07-26 19:57 ` Michael S. Tsirkin
2010-07-27 8:18 ` Tejun Heo
2010-07-26 16:51 ` Michael S. Tsirkin
2010-07-26 19:14 ` Tejun Heo
2010-07-26 19:31 ` Tejun Heo
2010-07-26 19:59 ` Michael S. Tsirkin
2010-07-27 19:19 ` Michael S. Tsirkin
2010-07-28 7:48 ` Tejun Heo
2010-07-28 10:48 ` Michael S. Tsirkin
2010-07-28 12:00 ` Tejun Heo
2010-07-26 16:57 ` Michael S. Tsirkin [this message]
2010-07-26 16:23 ` Michael S. Tsirkin
2010-07-26 19:04 ` Tejun Heo
2010-07-26 20:19 ` Michael S. Tsirkin
2010-07-27 8:21 ` Tejun Heo
2010-06-01 9:34 ` [PATCH 2/3] cgroups: Add an API to attach a task to current task's cgroup Tejun Heo
2010-06-01 9:35 ` [PATCH 3/3] vhost: apply cpumask and cgroup to vhost workers Tejun Heo
2010-06-01 10:17 ` Michael S. Tsirkin
2010-06-01 10:56 ` Tejun Heo
2010-06-01 17:19 ` Sridhar Samudrala
2010-06-01 23:59 ` Tejun Heo
2010-06-01 14:13 ` [PATCH 1/3] vhost: replace vhost_workqueue with per-vhost kthread Paul E. McKenney
2010-05-30 20:24 ` [PATCH 2/3] cgroups: Add an API to attach a task to current task's cgroup Tejun Heo
2010-05-31 1:07 ` Li Zefan
2010-05-31 7:00 ` Tejun Heo
2010-05-30 20:25 ` [PATCH 3/3] vhost: apply cpumask and cgroup to vhost pollers Tejun Heo
2010-05-31 1:11 ` Li Zefan
2010-05-31 6:58 ` [PATCH UPDATED " Tejun Heo
2010-05-31 7:48 ` Li Zefan
2010-05-31 10:20 ` [PATCH UPDATED2 " Tejun Heo
2010-06-24 8:11 ` [PATCH " Michael S. Tsirkin
2010-06-24 22:45 ` Sridhar Samudrala
2010-06-25 10:10 ` [PATCH] sched: export sched_set/getaffinity (was Re: [PATCH 3/3] vhost: apply cpumask and cgroup to vhost pollers) Michael S. Tsirkin
2010-07-01 11:07 ` [PATCH repost] sched: export sched_set/getaffinity to modules Michael S. Tsirkin
2010-07-01 11:19 ` Peter Zijlstra
2010-07-01 11:43 ` Peter Zijlstra
2010-07-01 11:55 ` Michael S. Tsirkin
2010-07-01 12:23 ` Michael S. Tsirkin
2010-07-01 12:34 ` Peter Zijlstra
2010-07-01 12:46 ` Peter Zijlstra
2010-07-01 13:08 ` Michael S. Tsirkin
2010-07-01 13:30 ` Peter Zijlstra
2010-07-01 13:39 ` Michael S. Tsirkin
2010-07-01 13:57 ` Peter Zijlstra
2010-07-01 14:27 ` Tejun Heo
2010-07-01 14:46 ` Oleg Nesterov
2010-07-01 14:53 ` Tejun Heo
2010-07-01 14:55 ` Peter Zijlstra
2010-07-02 18:01 ` Sridhar Samudrala
2010-07-02 18:11 ` Peter Zijlstra
2010-07-02 21:06 ` Oleg Nesterov
2010-07-04 9:00 ` Michael S. Tsirkin
2010-07-13 6:59 ` Sridhar Samudrala
2010-07-13 11:09 ` Michael S. Tsirkin
2010-07-14 23:26 ` Sridhar Samudrala
2010-07-15 0:05 ` Oleg Nesterov
2010-07-15 5:29 ` Sridhar Samudrala
2010-07-26 17:12 ` Michael S. Tsirkin
2010-07-26 17:51 ` Sridhar Samudrala
2010-07-26 18:08 ` Oleg Nesterov
2010-07-26 19:55 ` Michael S. Tsirkin
2010-07-26 20:27 ` Michael S. Tsirkin
2010-07-27 4:55 ` Michael S. Tsirkin
2010-08-04 10:45 ` Peter Zijlstra
2010-07-27 15:41 ` Michael S. Tsirkin
2010-07-30 14:19 ` Oleg Nesterov
2010-07-30 14:31 ` Tejun Heo
2010-08-01 8:50 ` Michael S. Tsirkin
2010-08-02 15:02 ` Oleg Nesterov
2010-07-01 14:33 ` Oleg Nesterov
2010-07-01 12:32 ` Peter Zijlstra
2010-07-01 12:50 ` Michael S. Tsirkin
2010-07-01 13:07 ` Peter Zijlstra
2010-07-01 13:22 ` Michael S. Tsirkin
2010-05-27 16:24 ` [PATCH 2/3] workqueue: Add an API to create a singlethread workqueue attached to the current task's cgroup Sridhar Samudrala
2010-05-27 16:41 ` Michael S. Tsirkin
2010-05-27 17:30 ` Oleg Nesterov
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