[PATCH] kthread: Export kthread_data()

[PATCH] kthread: Export kthread_data()

[Waiman Long]

When multiple kernel threads are created to cooperatively work on
a common task, we may need a convenient way to access data that are
specific to each kthread.

The kthread_data() function fits this need.  However, it was not
visible to kthreads started in a kernel module. To solve this problem,
the kthread_data() function is now exported allowing kthreads from
kernel modules to use it.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/kthread.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index cd50e99..a71d461 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -156,6 +156,7 @@ void *kthread_data(struct task_struct *task)
 {
 	return to_kthread(task)->data;
 }
+EXPORT_SYMBOL(kthread_data);
 
 /**
  * kthread_probe_data - speculative version of kthread_data()
-- 
1.8.3.1

Re: [PATCH] kthread: Export kthread_data()

[Peter Zijlstra]

On Fri, Feb 09, 2018 at 09:52:21AM -0500, Waiman Long wrote:
> When multiple kernel threads are created to cooperatively work on
> a common task, we may need a convenient way to access data that are
> specific to each kthread.
> 
> The kthread_data() function fits this need.  However, it was not
> visible to kthreads started in a kernel module. To solve this problem,
> the kthread_data() function is now exported allowing kthreads from
> kernel modules to use it.

No. Without an in-tree user, no export.

Re: [PATCH] kthread: Export kthread_data()

[Christoph Hellwig]

On Fri, Feb 09, 2018 at 09:52:21AM -0500, Waiman Long wrote:
> When multiple kernel threads are created to cooperatively work on
> a common task, we may need a convenient way to access data that are
> specific to each kthread.
> 
> The kthread_data() function fits this need.  However, it was not
> visible to kthreads started in a kernel module. To solve this problem,
> the kthread_data() function is now exported allowing kthreads from
> kernel modules to use it.

Please send this along wit hthe actual user of it.

Re: [PATCH] kthread: Export kthread_data()

[Waiman Long]

On 02/13/2018 10:50 AM, Christoph Hellwig wrote:
> On Fri, Feb 09, 2018 at 09:52:21AM -0500, Waiman Long wrote:
>> When multiple kernel threads are created to cooperatively work on
>> a common task, we may need a convenient way to access data that are
>> specific to each kthread.
>>
>> The kthread_data() function fits this need.  However, it was not
>> visible to kthreads started in a kernel module. To solve this problem,
>> the kthread_data() function is now exported allowing kthreads from
>> kernel modules to use it.
> Please send this along wit hthe actual user of it.

It is the developers of the dm-vdo/kvdo modules that would like to use
the kthread_data() function. See

https://github.com/dm-vdo/kvdo

Those modules have a bunch of kernel threads working on block storage
deduplication/compression.

-Longman

Re: [PATCH] kthread: Export kthread_data()

[Waiman Long]

On 02/13/2018 04:40 PM, Waiman Long wrote:
> On 02/13/2018 10:50 AM, Christoph Hellwig wrote:
>> On Fri, Feb 09, 2018 at 09:52:21AM -0500, Waiman Long wrote:
>>> When multiple kernel threads are created to cooperatively work on
>>> a common task, we may need a convenient way to access data that are
>>> specific to each kthread.
>>>
>>> The kthread_data() function fits this need.  However, it was not
>>> visible to kthreads started in a kernel module. To solve this problem,
>>> the kthread_data() function is now exported allowing kthreads from
>>> kernel modules to use it.
>> Please send this along wit hthe actual user of it.
> It is the developers of the dm-vdo/kvdo modules that would like to use
> the kthread_data() function. See
>
> https://github.com/dm-vdo/kvdo
>
> Those modules have a bunch of kernel threads working on block storage
> deduplication/compression.
>
> -Longman
>
BTW, I am fine with not exporting the function. They just have to find
an alternative way of doing it.

-Longman