lkml.org 
[lkml]   [2007]   [May]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH] relay: use plain timer instead of delayed work
From
Date
Hi,

This patch makes relay use timers instead of workqueues for reader
waking.

Tom

---

relay doesn't need to use schedule_delayed_work() for waking readers
when a simple timer will do.

Signed-off-by: Tom Zanussi <zanussi@comcast.net>
---

include/linux/relay.h | 2 +-
kernel/relay.c | 37 ++++++++++++++++++++-----------------
2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/include/linux/relay.h b/include/linux/relay.h
index 759a0f9..cac0732 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -38,7 +38,7 @@ struct rchan_buf
size_t subbufs_consumed; /* count of sub-buffers consumed */
struct rchan *chan; /* associated channel */
wait_queue_head_t read_wait; /* reader wait queue */
- struct delayed_work wake_readers; /* reader wake-up work struct */
+ struct timer_list timer; /* reader wake-up timer */
struct dentry *dentry; /* channel file dentry */
struct kref kref; /* channel buffer refcount */
struct page **page_array; /* array of current buffer pages */
diff --git a/kernel/relay.c b/kernel/relay.c
index 577f251..6b252be 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -310,16 +310,13 @@ static struct rchan_callbacks default_channel_callbacks = {

/**
* wakeup_readers - wake up readers waiting on a channel
- * @work: work struct that contains the the channel buffer
+ * @data: contains the the channel buffer
*
- * This is the work function used to defer reader waking. The
- * reason waking is deferred is that calling directly from write
- * causes problems if you're writing from say the scheduler.
+ * This is the timer function used to defer reader waking.
*/
-static void wakeup_readers(struct work_struct *work)
+static void wakeup_readers(unsigned long data)
{
- struct rchan_buf *buf =
- container_of(work, struct rchan_buf, wake_readers.work);
+ struct rchan_buf *buf = (struct rchan_buf *)data;
wake_up_interruptible(&buf->read_wait);
}

@@ -337,11 +334,11 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
if (init) {
init_waitqueue_head(&buf->read_wait);
kref_init(&buf->kref);
- INIT_DELAYED_WORK(&buf->wake_readers, NULL);
- } else {
- cancel_delayed_work(&buf->wake_readers);
- flush_scheduled_work();
- }
+ init_timer(&buf->timer);
+ buf->timer.data = (unsigned long)buf;
+ buf->timer.function = wakeup_readers;
+ } else
+ del_timer_sync(&buf->timer);

buf->subbufs_produced = 0;
buf->subbufs_consumed = 0;
@@ -447,8 +444,7 @@ end:
static void relay_close_buf(struct rchan_buf *buf)
{
buf->finalized = 1;
- cancel_delayed_work(&buf->wake_readers);
- flush_scheduled_work();
+ del_timer_sync(&buf->timer);
kref_put(&buf->kref, relay_remove_buf);
}

@@ -609,9 +605,16 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
buf->padding[old_subbuf];
smp_mb();
if (waitqueue_active(&buf->read_wait)) {
- PREPARE_DELAYED_WORK(&buf->wake_readers,
- wakeup_readers);
- schedule_delayed_work(&buf->wake_readers, 1);
+ /*
+ * Calling wake_up_interruptible() from here
+ * will deadlock if we happen to be logging
+ * from the scheduler (trying to re-grab
+ * rq->lock), so defer it.
+ */
+ if (!timer_pending(&buf->timer)) {
+ buf->timer.expires = jiffies + 1;
+ add_timer(&buf->timer);
+ }
}
}



-
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/

\
 
 \ /
  Last update: 2007-05-06 07:41    [W:0.100 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site