Re: [PATCH] perf build: Improve fix for "argument list too long" error

[sashiko-bot@kernel.org]

> The orphaned pmu-events JSON files are passed to the shell via
> `echo "$^"`, which puts the whole list into a single argument. With
> a long enough output directory path and enough files, exec'ing
> /bin/sh fails with:
> 
>   make[5]: /bin/sh: Argument list too long
>   make[5]: *** [pmu-events/Build:228: prune_orphans] Error 127
> 
> This only happens with out-of-tree builds, when setting O= to a
> relatively long path.
> 
> To reproduce, build once with JEVENTS_ARCH=all, then rebuild with
> a smaller JEVENTS_ARCH without cleaning first, so the leftover files
> become orphans. Using nds32 (which leaves ~1100 orphans), an output
> path of only ~70 characters is already enough to trigger it:
> 
>   OUT=/any/long/path (at least 70 characters)
>   make -C tools/perf JEVENTS_ARCH=all   O=$OUT -j$(nproc)
>   make -C tools/perf JEVENTS_ARCH=nds32 O=$OUT -j$(nproc)
> 
> Express the orphan file list as paths relative to $(OUT_DIR) by
> stripping the common prefix and restoring it with printf, the same
> approach used in scripts/Makefile.clean, so the shell arguments stay
> short.
> 
> Fixes: b6712d91f8f5 ("perf build: Prevent "argument list too long" error")
> Suggested-by: Vladimir Kondratiev <vladimir.kondratiev@mobileye.com>
> Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260928-perf-orphan-args-v1-1-8cacf784621e@bootlin.com?part=1