Re: [PATCH] workqueue: Make a warning when a pending delay work being re-init

[Mukesh Ojha]

On 11/15/2023 5:04 PM, huangzaiyang wrote:
> There is a timer_list race condition if a delay work is queued twice,
> this usually won't happen unless someone reinitializes the task before performing the enqueue operation,likeï¼?
> https://github.com/torvalds/linux/blob/master/drivers/devfreq/devfreq.c#L487
> A warning message will help developers identify this irregular usage.
>
> Signed-off-by: ZaiYang Huang <hzy0719@xxxxxxx>

I like the idea to have this for developers.

Acked-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>

> ---
>   include/linux/workqueue.h | 33 ++++++++++++++++++---------------
>   1 file changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
> index 24b1e5070f4d..54102ed794e5 100644
> --- a/include/linux/workqueue.h
> +++ b/include/linux/workqueue.h
> @@ -266,6 +266,22 @@ static inline void destroy_delayed_work_on_stack(struct delayed_work *work) { }
>   static inline unsigned int work_static(struct work_struct *work) { return 0; }
>   #endif
>
> +/**
> + * work_pending - Find out whether a work item is currently pending
> + * @work: The work item in question
> + */
> +#define work_pending(work) \
> +       test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))
> +
> +/**
> + * delayed_work_pending - Find out whether a delayable work item is currently
> + * pending
> + * @w: The work item in question
> + */
> +#define delayed_work_pending(w) \
> +       work_pending(&(w)->work)
> +
> +
>   /*
>    * initialize all of a work item in one go
>    *
> @@ -310,6 +326,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
>
>   #define __INIT_DELAYED_WORK(_work, _func, _tflags)                     \
>          do {                                                            \
> +               WARN_ON(delayed_work_pending(_work));                   \
>                  INIT_WORK(&(_work)->work, (_func));                     \
>                  __init_timer(&(_work)->timer,                           \
>                               delayed_work_timer_fn,                     \
> @@ -318,6 +335,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
>
>   #define __INIT_DELAYED_WORK_ONSTACK(_work, _func, _tflags)             \
>          do {                                                            \
> +               WARN_ON(delayed_work_pending(_work));

However, I don't think it will be applicable for _ONSTACK variable as it
is on stack.
                   \
>                  INIT_WORK_ONSTACK(&(_work)->work, (_func));             \
>                  __init_timer_on_stack(&(_work)->timer,                  \
>                                        delayed_work_timer_fn,            \
> @@ -342,21 +360,6 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
>   #define INIT_RCU_WORK_ONSTACK(_work, _func)                            \
>          INIT_WORK_ONSTACK(&(_work)->work, (_func))
>
> -/**
> - * work_pending - Find out whether a work item is currently pending
> - * @work: The work item in question
> - */
> -#define work_pending(work) \
> -       test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))
> -
> -/**
> - * delayed_work_pending - Find out whether a delayable work item is currently
> - * pending
> - * @w: The work item in question
> - */
> -#define delayed_work_pending(w) \
> -       work_pending(&(w)->work)
> -
>   /*
>    * Workqueue flags and constants.  For details, please refer to
>    * Documentation/core-api/workqueue.rst.
> --
> 2.17.1

Please remove this ..

-Mukesh
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