Re: [PATCH v5 3/5] percpu-refcount: add refcount_final_put tracepoint

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The tracepoint incorrectly uses `_RET_IP_` in a `static inline` function, causing it to report the caller's caller instead of the actual caller depending on compiler inlining.
--

--- Patch [3]: [PATCH v5 3/5] percpu-refcount: add refcount_final_put tracepoint ---
commit 9f895c01ce2cdf26a289904e12ffb409aa7dc2a0
Author: Eugene Mavick <[email protected]>

percpu-refcount: add refcount_final_put tracepoint

This commit adds the refcount_final_put tracepoint to the atomic fallback
path in percpu_ref_put_many(). It fires when the atomic counter reaches
zero, recording the caller function, the instruction pointer, and the
refcount object.

> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
> index d73a1c08c3e3c..244992b2f746e 100644
> --- a/include/linux/percpu-refcount.h
> +++ b/include/linux/percpu-refcount.h

[ ... ]

> @@ -331,8 +332,10 @@ static inline void percpu_ref_put_many(struct percpu_ref *ref, unsigned long nr)
>  
>  	if (__ref_is_percpu(ref, &percpu_count))
>  		this_cpu_sub(*percpu_count, nr);
> -	else if (unlikely(atomic_long_sub_and_test(nr, &ref->data->count)))
> +	else if (unlikely(atomic_long_sub_and_test(nr, &ref->data->count))) {
> +		do_trace_refcount_final_put(ref);

[Severity: Medium]
Since percpu_ref_put_many() is a static inline function, won't using _RET_IP_
inside the trace macro evaluate to the caller's caller when inlined?

When inlined by the compiler, _RET_IP_ (which expands to
__builtin_return_address(0)) will yield the instruction pointer of the
enclosing function rather than the caller of percpu_ref_put_many().

Could the instruction pointer be passed as an explicit argument from the call
site instead?

>  		ref->data->release(ref);
> +	}
>  
>  	rcu_read_unlock();
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=3