[PATCH] kthread: Mark timer used by delayed kthread works as IRQ safe

[PATCH] kthread: Mark timer used by delayed kthread works as IRQ safe

[Petr Mladek]

The timer used by delayed kthread works are IRQ safe because the used
kthread_delayed_work_timer_fn() is IRQ safe.

It is properly marked when initialized by KTHREAD_DELAYED_WORK_INIT().
But TIMER_IRQSAFE flag is missing when initialized by
kthread_init_delayed_work().

The missing flag might trigger invalid warning from del_timer_sync()
when kthread_mod_delayed_work() is called with interrupts disabled.

Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
This patch is result of a discussion about using the API, see
https://lkml.kernel.org/r/cfa886ad-e3b7-c0d2-3ff8-58d94170eab5@ti.com

 include/linux/kthread.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 0f9da966934e..8bbcaad7ef0f 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -165,7 +165,8 @@ extern void __kthread_init_worker(struct kthread_worker *worker,
 	do {								\
 		kthread_init_work(&(dwork)->work, (fn));		\
 		timer_setup(&(dwork)->timer,				\
-			     kthread_delayed_work_timer_fn, 0);		\
+			     kthread_delayed_work_timer_fn,		\
+			     TIMER_IRQSAFE);				\
 	} while (0)
 
 int kthread_worker_fn(void *worker_ptr);
-- 
2.16.4

Re: [PATCH] kthread: Mark timer used by delayed kthread works as IRQ safe

[Tejun Heo]

On Mon, Feb 17, 2020 at 01:07:09PM +0100, Petr Mladek wrote:
> The timer used by delayed kthread works are IRQ safe because the used
> kthread_delayed_work_timer_fn() is IRQ safe.
> 
> It is properly marked when initialized by KTHREAD_DELAYED_WORK_INIT().
> But TIMER_IRQSAFE flag is missing when initialized by
> kthread_init_delayed_work().
> 
> The missing flag might trigger invalid warning from del_timer_sync()
> when kthread_mod_delayed_work() is called with interrupts disabled.
> 
> Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
> Signed-off-by: Petr Mladek <pmladek@suse.com>
> Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH] kthread: Mark timer used by delayed kthread works as IRQ safe

[Grygorii Strashko]

Hi Petr,

On 19/02/2020 17:22, Tejun Heo wrote:
> On Mon, Feb 17, 2020 at 01:07:09PM +0100, Petr Mladek wrote:
>> The timer used by delayed kthread works are IRQ safe because the used
>> kthread_delayed_work_timer_fn() is IRQ safe.
>>
>> It is properly marked when initialized by KTHREAD_DELAYED_WORK_INIT().
>> But TIMER_IRQSAFE flag is missing when initialized by
>> kthread_init_delayed_work().
>>
>> The missing flag might trigger invalid warning from del_timer_sync()
>> when kthread_mod_delayed_work() is called with interrupts disabled.
>>
>> Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
>> Signed-off-by: Petr Mladek <pmladek@suse.com>
>> Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
> 
> Acked-by: Tejun Heo <tj@kernel.org>

I'm worry shouldn't this patch have "fixes" tag?

-- 
Best regards,
grygorii

Re: [PATCH] kthread: Mark timer used by delayed kthread works as IRQ safe

[Grygorii Strashko]

Hi All,

On 16/03/2020 14:23, Grygorii Strashko wrote:
> Hi Petr,
> 
> On 19/02/2020 17:22, Tejun Heo wrote:
>> On Mon, Feb 17, 2020 at 01:07:09PM +0100, Petr Mladek wrote:
>>> The timer used by delayed kthread works are IRQ safe because the used
>>> kthread_delayed_work_timer_fn() is IRQ safe.
>>>
>>> It is properly marked when initialized by KTHREAD_DELAYED_WORK_INIT().
>>> But TIMER_IRQSAFE flag is missing when initialized by
>>> kthread_init_delayed_work().
>>>
>>> The missing flag might trigger invalid warning from del_timer_sync()
>>> when kthread_mod_delayed_work() is called with interrupts disabled.
>>>
>>> Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>> Signed-off-by: Petr Mladek <pmladek@suse.com>
>>> Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>
>> Acked-by: Tejun Heo <tj@kernel.org>
> 
> I'm worry shouldn't this patch have "fixes" tag?
> 

Sorry, the I'm disturbing you, but I have dependency from this path [1].
I can see it in -next: commit d7c8c7de96de ("kthread: mark timer used by
delayed kthread works as IRQ safe"), but it does not present in net-next.

Any way this can be resolved?

[1] https://patchwork.ozlabs.org/cover/1259207/
-- 
Best regards,
grygorii