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

[James Clark]

On 28/09/2026 09:55, Benoît Monin wrote:
> 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@xxxxxxxxxxxx>
> Signed-off-by: Benoît Monin <benoit.monin@xxxxxxxxxxx>
> Tested-by: Vladimir Kondratiev <vladimir.kondratiev@xxxxxxxxxxxx>

Reviewed-by: James Clark <james.clark@xxxxxxxxxx>