Re: [PATCH v6 5/8] perf cs-etm: Support call indentation

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The condition for swapping packets in `cs_etm__packet_swap()` was not updated to include the new `use_thread_stack` flag, which breaks the `callindent` feature if branch and instruction sampling are disabled.
--

commit 36aa886e2c5be33efb8d11e03a02df7c74dce99b
Author: Leo Yan <leo.yan@linux.dev>

perf cs-etm: Support call indentation
    
This commit introduces a use_thread_stack flag to track whether the branch
stack needs to be recorded. This allows call indentation to function
independently of the last branch record feature.

[ ... ]

> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index ea2424175558d..b31d0dd46a45d 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c

[ ... ]

> @@ -1914,7 +1915,7 @@ static int cs_etm__flush(struct cs_etm_queue *etmq,
>  	cs_etm__packet_swap(etm, tidq);

[Severity: Medium]
Will this swap logic still work if branch and instruction sampling are
disabled?

Looking at cs_etm__packet_swap(), the condition to perform the swap was not
updated to check the new use_thread_stack flag:

tools/perf/util/cs-etm.c:cs_etm__packet_swap() {
    if (etm->synth_opts.branches || etm->synth_opts.last_branch ||
        etm->synth_opts.instructions) {
        ...
        // swap packets
    }
}

If a user runs perf script -F +callindent without enabling branches,
last_branch, or instructions, cs_etm__packet_swap() won't swap the packets.

Does the previous packet remaining empty prevent the thread stack from being
populated, causing callindent to silently fail?

Could cs_etm__packet_swap() be updated to check use_thread_stack as well?

>  
>  	/* Reset last branches after flush the trace */
> -	if (etm->synth_opts.last_branch)
> +	if (etm->use_thread_stack)
>  		thread_stack__flush(tidq->thread);
>  
>  	return err;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260526-b4-arm_cs_callchain_support_v1-v6-0-f9f49f53c9dd@arm.com?part=5