Re: [PATCH v13 09/14] unwind deferred: Use SRCU unwind_deferred_task_work()

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 14 Jul 2025 15:56:38 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> Please; something like so:
> 
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -524,4 +524,9 @@ DEFINE_LOCK_GUARD_1(srcu, struct srcu_st
>  		    srcu_read_unlock(_T->lock, _T->idx),
>  		    int idx)
>  
> +DEFINE_LOCK_GUARD_1(srcu_lite, struct srcu_struct,
> +		    _T->idx = srcu_read_lock_lite(_T->lock),
> +		    srcu_read_unlock_lite(_T->lock, _T->idx),
> +		    int idx)
> +
>  #endif
> --- a/kernel/unwind/deferred.c
> +++ b/kernel/unwind/deferred.c
> @@ -165,7 +165,7 @@ static void unwind_deferred_task_work(st
>  
>  	cookie = info->id.id;
>  
> -	guard(mutex)(&callback_mutex);
> +	guard(srcu_lite)(&unwind_srcu);
>  	list_for_each_entry(work, &callbacks, list) {
>  		work->func(work, &trace, cookie);
>  	}

I think I rather have a scoped_guard() here. One thing that bothers me
about the guard() logic is that it could easily start to "leak"
protection. That is, the unwind_srcu is only needed for walking the
list. The reason I chose to open code the protection, is because I
wanted to distinctly denote where the end of the protection was.

-- Steve