Re: [PATCH] perf test: waiting.sh: Replace timestamp polling with sleep

[sashiko-bot@kernel.org]

> The waiting helpers implement timeouts using:
> 
>   date +%s%1N
> 
> This relies on GNU coreutils date truncating %N to the specified width,
> so %1N yields tenths of a second.
> 
> Rust coreutils (uutils) interprets the width differently and does not
> truncate the nanoseconds field.  Consequently "date +%1N" returns all
> nine nanosecond digits, causing the elapsed-time calculation to be done
> in nanoseconds while timeout values remain in tenths of a second.
> 
> As a result, timeout comparisons succeed immediately and the waiting
> helpers time out on their first iteration.  This causes
> test_intel_pt.sh to fail on systems using uutils "date".
> 
> Avoid implementation-specific date formatting entirely.  Instead, wait
> for 100 ms on each iteration and count the timeout down.  Besides fixing
> the portability issue, this removes the busy-waiting behaviour in
> wait_for_perf_to_start(), which could otherwise consume CPU while
> waiting for perf record to start.
> 
> Since the timeout is now based on repeated sleeps, it is only
> approximate.  Update the comments accordingly.  Also make is_running()
> wait for exactly the documented number of tenths by changing its timeout
> test from -gt to the new logic, and quote tm_out in the modified code.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260908152053.192830-1-adrian.hunter@intel.com?part=1