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Date: Wed, 15 Nov 2023 22:14:05 +0100
From: Thomas Weißschuh <thomas@...ch.de>
To: huangzaiyang <huangzaiyang@...o.com>
Cc: tj@...nel.org, jiangshanlai@...il.com,
linux-kernel@...r.kernel.org, ZaiYang Huang <hzy0719@....com>,
Mukesh Ojha <quic_mojha@...cinc.com>
Subject: Re: [PATCH] workqueue: Make a warning when a pending delay work
being re-init
On 2023-11-15 19:34:27+0800, 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@....com>
> ---
> 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)); \
How does this work when the data _work points to is not yet initialized?
Reading uninitialized data is UB and may spuriously trigger the warning.
> 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; }
[..]
> --
> 2.17.1
>
> ________________________________
> OPPO
The gunk at the end of the mail will prevent your patch from being
considered at all.
>
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[..]
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