>From 8fcd63664f1185361d00be4fe2decc2b9da8330e Mon Sep 17 00:00:00 2001
From: Tejun Heo <t...@kernel.org>
Date: Wed, 8 Aug 2012 09:38:42 -0700
delayed_work encodes the workqueue to use and the last CPU in
delayed_work->work.data while it's on timer. The target CPU is
implicitly recorded as the CPU the timer is queued on and
delayed_work_timer_fn() queues delayed_work->work to the CPU it is
running on.
Unfortunately, this leaves flush_delayed_work[_sync]() no way to find
out which CPU the delayed_work was queued for when they try to
re-queue after killing the timer. Currently, it chooses the local CPU
flush is running on. This can unexpectedly move a delayed_work queued
on a specific CPU to another CPU and lead to subtle errors.
There isn't much point in trying to save several bytes in struct
delayed_work, which is already close to a hundred bytes on 64bit with
all debug options turned off. This patch adds delayed_work->cpu to
remember the CPU it's queued for.
Note that if the timer is migrated during CPU down, the work item
could be queued to the downed global_cwq after this change. As a
detached global_cwq behaves like an unbound one, this doesn't change
much for the delayed_work.
Signed-off-by: Tejun Heo <t...@kernel.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Andrew Morton <a...@linux-foundation.org>
---
While this is a fix, I don't think any current user is affected. I'll
route this through wq/for-3.7.
Thanks.
include/linux/workqueue.h | 1 +
kernel/workqueue.c | 7 ++++---
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 2000030..b14d5d5 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -102,6 +102,7 @@ struct work_struct {
struct delayed_work {
struct work_struct work;
struct timer_list timer;
+ int cpu;
};
static inline struct delayed_work *to_delayed_work(struct work_struct *work)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 41ae2c0..11723c5 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1319,7 +1319,7 @@ void delayed_work_timer_fn(unsigned long __data)
struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
local_irq_disable();
- __queue_work(WORK_CPU_UNBOUND, cwq->wq, &dwork->work);
+ __queue_work(dwork->cpu, cwq->wq, &dwork->work);
local_irq_enable();
}
EXPORT_SYMBOL_GPL(delayed_work_timer_fn);
@@ -1356,6 +1356,7 @@ static void __queue_delayed_work(int cpu, struct
workqueue_struct *wq,
set_work_cwq(work, get_cwq(lcpu, wq), 0);
+ dwork->cpu = cpu;
timer->expires = jiffies + delay;
if (unlikely(cpu != WORK_CPU_UNBOUND))
@@ -2997,7 +2998,7 @@ bool flush_delayed_work(struct delayed_work *dwork)
{
local_irq_disable();
if (del_timer_sync(&dwork->timer))
- __queue_work(WORK_CPU_UNBOUND,
+ __queue_work(dwork->cpu,
get_work_cwq(&dwork->work)->wq, &dwork->work);
local_irq_enable();
return flush_work(&dwork->work);
@@ -3020,7 +3021,7 @@ bool flush_delayed_work_sync(struct delayed_work *dwork)
{
local_irq_disable();
if (del_timer_sync(&dwork->timer))
- __queue_work(WORK_CPU_UNBOUND,
+ __queue_work(dwork->cpu,
get_work_cwq(&dwork->work)->wq, &dwork->work);
local_irq_enable();
return flush_work_sync(&dwork->work);
--
1.7.7.3
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