[PATCH] workqueue: show the pool ID of the default pwq's pool in the pool_ids file

[PATCH] workqueue: show the pool ID of the default pwq's pool in the pool_ids file

[Lai Jiangshan]

It seems incomplete if the pool_ids file doesn't include the default
pwq's pool.  Add it and the result:

# cat pool_ids 
0:9 1:10
default:8

rcu_read_lock_sched() is also changed to mutex_lock(&wq->mutex)
for accessing the default pwq.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/workqueue.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 5dbe22a..6af95210 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3004,7 +3004,7 @@ static ssize_t wq_pool_ids_show(struct device *dev,
 	const char *delim = "";
 	int node, written = 0;
 
-	rcu_read_lock_sched();
+	mutex_lock(&wq->mutex);
 	for_each_node(node) {
 		written += scnprintf(buf + written, PAGE_SIZE - written,
 				     "%s%d:%d", delim, node,
@@ -3012,7 +3012,9 @@ static ssize_t wq_pool_ids_show(struct device *dev,
 		delim = " ";
 	}
 	written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
-	rcu_read_unlock_sched();
+	written += scnprintf(buf + written, PAGE_SIZE - written,
+			     "default:%d\n", wq->dfl_pwq->pool->id);
+	mutex_unlock(&wq->mutex);
 
 	return written;
 }
-- 
1.7.4.4

Re: [PATCH] workqueue: show the pool ID of the default pwq's pool in the pool_ids file

[Tejun Heo]

On Mon, Sep 22, 2014 at 04:04:37PM +0800, Lai Jiangshan wrote:
> It seems incomplete if the pool_ids file doesn't include the default
> pwq's pool.  Add it and the result:
> 
> # cat pool_ids 
> 0:9 1:10
> default:8

Hmmm?  default pwq is used only as the fallback if pool switching
fails and the failed nodes will have it assigned to them.  Why would
userland care about something which isn't being used?

Thanks.

-- 
tejun

Re: [PATCH] workqueue: show the pool ID of the default pwq's pool in the pool_ids file

[Lai Jiangshan]

On 09/23/2014 10:38 PM, Tejun Heo wrote:
> On Mon, Sep 22, 2014 at 04:04:37PM +0800, Lai Jiangshan wrote:
>> It seems incomplete if the pool_ids file doesn't include the default
>> pwq's pool.  Add it and the result:
>>
>> # cat pool_ids 
>> 0:9 1:10
>> default:8
> 
> Hmmm?  default pwq is used only as the fallback if pool switching
> fails and the failed nodes will have it assigned to them.  Why would
> userland care about something which isn't being used?

Understood.

> 
> Thanks.
>