Re: [PATCH v2 12/14] perf test: Allow infinite named_thread loops

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The intentional infinite loop in test threads can be optimized away by the compiler, violating the requirement that they run forever.
--

--- Patch [12]: [PATCH v2 12/14] perf test: Allow infinite named_thread loops ---
commit 53c8a5e547e7365781e369ccbc9c9f225381027d
Author: James Clark <[email protected]>

perf test: Allow infinite named_thread loops

This commit modifies the named_threads workload in perf tests to run
infinitely when 0 is passed for the loop count. It also converts the loop
counter and work variable to unsigned integers to prevent undefined behavior
from signed overflow.

> diff --git a/tools/perf/tests/workloads/named_threads.c b/tools/perf/tests/workloads/named_threads.c
> index d051d41a3cfe4..6672c2f776840 100644
> --- a/tools/perf/tests/workloads/named_threads.c
> +++ b/tools/perf/tests/workloads/named_threads.c
[ ... ]
> @@ -19,7 +19,8 @@ typedef void *(*thread_fn_t)(void *);
>  noinline void *named_threads_thread##n(void *arg __maybe_unused)	\
>  {									\
>  	pthread_setname_np(pthread_self(), "thread" #n);		\
> -	for (int i = 0; i < iterations; i++)				\
> +	for (unsigned int i = 0;					\
> +	     i < (unsigned int) iterations || iterations == 0; i++)	\
>  		named_threads_work += 3;				\

[Severity: Medium]
Will this loop in DEFINE_THREAD() be optimized away by the compiler when
iterations == 0?

Because named_threads_work is not volatile and the loop lacks a compiler barrier
or cpu_relax(), the compiler might assume the loop terminates and eliminate it
entirely.

Could this cause the test threads to exit immediately instead of generating
continuous CPU cycles as intended?

>  									\
>  	return NULL;							\
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260821-james-cs-unformatted-per-thread-fix-v2-0-00c4fd0701b4@linaro.org?part=12