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Date: Fri, 1 Jun 2012 05:24:03 -0700
From: Anton Vorontsov <anton.vorontsov@...aro.org>
To: Pekka Enberg <penberg@...nel.org>
Cc: Leonid Moiseichuk <leonid.moiseichuk@...ia.com>,
KOSAKI Motohiro <kosaki.motohiro@...il.com>,
Minchan Kim <minchan@...nel.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
John Stultz <john.stultz@...aro.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
patches@...aro.org, kernel-team@...roid.com
Subject: [PATCH 2/5] vmevent: Convert from deferred timer to deferred work
We'll need to use smp_function_call() in the sampling routines, and the
call is not supposed to be called from the bottom halves. So, let's
convert vmevent to dffered workqueues.
As a side effect, we also fix the swap reporting (we cannot call
si_swapinfo from the interrupt context), i.e. the following oops should
be fixed now:
=================================
[ INFO: inconsistent lock state ]
3.4.0-rc1+ #37 Not tainted
---------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
(swap_lock){+.?...}, at: [<ffffffff8110449d>] si_swapinfo+0x1d/0x90
{SOFTIRQ-ON-W} state was registered at:
[<ffffffff8107ca7f>] mark_irqflags+0x15f/0x1b0
[<ffffffff8107e5e3>] __lock_acquire+0x493/0x9d0
[<ffffffff8107f20e>] lock_acquire+0x9e/0x200
[<ffffffff813e9071>] _raw_spin_lock+0x41/0x50
[<ffffffff8110449d>] si_swapinfo+0x1d/0x90
[<ffffffff8117e7c8>] meminfo_proc_show+0x38/0x3f0
[<ffffffff81141209>] seq_read+0x139/0x3f0
[<ffffffff81174cc6>] proc_reg_read+0x86/0xc0
[<ffffffff8111c19c>] vfs_read+0xac/0x160
[<ffffffff8111c29a>] sys_read+0x4a/0x90
[<ffffffff813ea652>] system_call_fastpath+0x16/0x1b
Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
---
mm/vmevent.c | 49 ++++++++++++++++++++++++++++---------------------
1 file changed, 28 insertions(+), 21 deletions(-)
diff --git a/mm/vmevent.c b/mm/vmevent.c
index 381e9d1..4ca2a04 100644
--- a/mm/vmevent.c
+++ b/mm/vmevent.c
@@ -3,7 +3,7 @@
#include <linux/compiler.h>
#include <linux/vmevent.h>
#include <linux/syscalls.h>
-#include <linux/timer.h>
+#include <linux/workqueue.h>
#include <linux/file.h>
#include <linux/list.h>
#include <linux/poll.h>
@@ -34,7 +34,7 @@ struct vmevent_watch {
struct vmevent_attr *config_attrs[VMEVENT_CONFIG_MAX_ATTRS];
/* sampling */
- struct timer_list timer;
+ struct delayed_work work;
/* poll */
wait_queue_head_t waitq;
@@ -146,15 +146,13 @@ static bool vmevent_match(struct vmevent_watch *watch)
}
/*
- * This function is called from the timer context, which has the same
- * guaranties as an interrupt handler: it can have only one execution
- * thread (unlike bare softirq handler), so we don't need to worry
- * about racing w/ ourselves.
+ * This function is called from a workqueue, which can have only one
+ * execution thread, so we don't need to worry about racing w/ ourselves.
*
- * We also don't need to worry about several instances of timers
- * accessing the same vmevent_watch, as we allocate vmevent_watch
- * together w/ the timer instance in vmevent_fd(), so there is always
- * one timer per vmevent_watch.
+ * We also don't need to worry about several instances of us accessing
+ * the same vmevent_watch, as we allocate vmevent_watch together w/ the
+ * work instance in vmevent_fd(), so there is always one work per
+ * vmevent_watch.
*
* All the above makes it possible to implement the lock-free logic,
* using just the atomic watch->pending variable.
@@ -178,26 +176,35 @@ static void vmevent_sample(struct vmevent_watch *watch)
atomic_set(&watch->pending, 1);
}
-static void vmevent_timer_fn(unsigned long data)
+static void vmevent_schedule_watch(struct vmevent_watch *watch)
{
- struct vmevent_watch *watch = (struct vmevent_watch *)data;
+ schedule_delayed_work(&watch->work,
+ nsecs_to_jiffies64(watch->config.sample_period_ns));
+}
+
+static struct vmevent_watch *work_to_vmevent_watch(struct work_struct *work)
+{
+ struct delayed_work *wk = to_delayed_work(work);
+
+ return container_of(wk, struct vmevent_watch, work);
+}
+
+static void vmevent_timer_fn(struct work_struct *work)
+{
+ struct vmevent_watch *watch = work_to_vmevent_watch(work);
vmevent_sample(watch);
if (atomic_read(&watch->pending))
wake_up(&watch->waitq);
- mod_timer(&watch->timer, jiffies +
- nsecs_to_jiffies64(watch->config.sample_period_ns));
+
+ vmevent_schedule_watch(watch);
}
static void vmevent_start_timer(struct vmevent_watch *watch)
{
- init_timer_deferrable(&watch->timer);
- watch->timer.data = (unsigned long)watch;
- watch->timer.function = vmevent_timer_fn;
- watch->timer.expires = jiffies +
- nsecs_to_jiffies64(watch->config.sample_period_ns);
- add_timer(&watch->timer);
+ INIT_DELAYED_WORK_DEFERRABLE(&watch->work, vmevent_timer_fn);
+ vmevent_schedule_watch(watch);
}
static unsigned int vmevent_poll(struct file *file, poll_table *wait)
@@ -259,7 +266,7 @@ static int vmevent_release(struct inode *inode, struct file *file)
{
struct vmevent_watch *watch = file->private_data;
- del_timer_sync(&watch->timer);
+ cancel_delayed_work_sync(&watch->work);
kfree(watch);
--
1.7.9.2
--
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