linux-kernel - Re: [PATCH v3 4/9] perf build: Disable thread safety analysis for perl header

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Message-ID: <CAP-5=fUVs8Dn+kQDgPW08SNC=W5ZQKMFEETjjqkOJ_Mvbv22dw@mail.gmail.com>
Date: Mon, 6 Oct 2025 10:56:43 -0700
From: Ian Rogers <irogers@...gle.com>
To: Leo Yan <leo.yan@....com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Alexandre Ghiti <alex@...ti.fr>, James Clark <james.clark@...aro.org>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, llvm@...ts.linux.dev, 
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 4/9] perf build: Disable thread safety analysis for
 perl header

On Mon, Oct 6, 2025 at 9:21 AM Leo Yan <leo.yan@....com> wrote:
>
> When build with perl5, it reports error:
>
>     In file included from /usr/lib/perl5/5.42.0/x86_64-linux-thread-multi/CORE/perl.h:7933:
>     /usr/lib/perl5/5.42.0/x86_64-linux-thread-multi/CORE/inline.h:298:5: error:
>           mutex 'PL_env_mutex.lock' is not held on every path through
>           here [-Werror,-Wthread-safety-analysis]
>       298 |     ENV_UNLOCK;
>           |     ^
>     /usr/lib/perl5/5.42.0/x86_64-linux-thread-multi/CORE/perl.h:7091:31: note:
>           expanded from macro 'ENV_UNLOCK'
>      7091 | #  define ENV_UNLOCK          PERL_REENTRANT_UNLOCK("env"...
>           |                               ^
>     /usr/lib/perl5/5.42.0/x86_64-linux-thread-multi/CORE/perl.h:6465:7: note:
>           expanded from macro 'PERL_REENTRANT_UNLOCK'
>      6465 |     } STMT_END
>           |       ^
>     /usr/lib/perl5/5.42.0/x86_64-linux-thread-multi/CORE/perl.h:865:28: note:
>           expanded from macro 'STMT_END'
>       865 | #   define STMT_END     while (0)
>           |                                ^
>
> The error is caused by perl header but not perf code, disable thread
> safety analysis if including the header.
>
> Though GCC does not support the thread safety analysis option, this
> negative warning flag is silently ignored by it.
>
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
>  tools/perf/scripts/perl/Perf-Trace-Util/Build | 2 +-
>  tools/perf/util/scripting-engines/Build       | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/scripts/perl/Perf-Trace-Util/Build b/tools/perf/scripts/perl/Perf-Trace-Util/Build
> index 9b0e5a8b5070f1a1640518fae75557f824ef21ee..01a1a0ed51aefd721b4bc7eba728c29a8ffcd551 100644
> --- a/tools/perf/scripts/perl/Perf-Trace-Util/Build
> +++ b/tools/perf/scripts/perl/Perf-Trace-Util/Build
> @@ -2,7 +2,7 @@ perf-util-y += Context.o
>
>  CFLAGS_Context.o += $(PERL_EMBED_CCOPTS) -Wno-redundant-decls -Wno-strict-prototypes -Wno-bad-function-cast -Wno-declaration-after-statement -Wno-switch-enum
>  CFLAGS_Context.o += -Wno-unused-parameter -Wno-nested-externs -Wno-undef
> -CFLAGS_Context.o += -Wno-switch-default -Wno-shadow
> +CFLAGS_Context.o += -Wno-switch-default -Wno-shadow -Wno-thread-safety-analysis

I wasn't able to reproduce this on Debian with perf-tools-next and:
make -C tools/perf O=/tmp/perf DEBUG=1 CC=clang CXX=clang++
HOSTCC=clang LIBPERL=1 clean all
but my libperl is 5.40. I'm a little concerned that the warning may
cause an unrecognized compiler option warning/error with GCC given
progress on thread-safety-analysis has ended there. Anyway, these
aren't blockers.

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

>
>  ifeq ($(CC_NO_CLANG), 1)
>    CFLAGS_Context.o += -Wno-unused-command-line-argument
> diff --git a/tools/perf/util/scripting-engines/Build b/tools/perf/util/scripting-engines/Build
> index 2282fe3772f3bdc35056cb5e66efb3462dc1c2e3..24f087b0cd11b3e06a338c394dc2c650bc2c60b1 100644
> --- a/tools/perf/util/scripting-engines/Build
> +++ b/tools/perf/util/scripting-engines/Build
> @@ -3,7 +3,7 @@ ifeq ($(CONFIG_LIBTRACEEVENT),y)
>  endif
>  perf-util-$(CONFIG_LIBPYTHON) += trace-event-python.o
>
> -CFLAGS_trace-event-perl.o += $(PERL_EMBED_CCOPTS) -Wno-redundant-decls -Wno-strict-prototypes -Wno-unused-parameter -Wno-shadow -Wno-nested-externs -Wno-undef -Wno-switch-default -Wno-bad-function-cast -Wno-declaration-after-statement -Wno-switch-enum
> +CFLAGS_trace-event-perl.o += $(PERL_EMBED_CCOPTS) -Wno-redundant-decls -Wno-strict-prototypes -Wno-unused-parameter -Wno-shadow -Wno-nested-externs -Wno-undef -Wno-switch-default -Wno-bad-function-cast -Wno-declaration-after-statement -Wno-switch-enum -Wno-thread-safety-analysis
>
>  # -Wno-declaration-after-statement: The python headers have mixed code with declarations (decls after asserts, for instance)
>  CFLAGS_trace-event-python.o += $(PYTHON_EMBED_CCOPTS) -Wno-redundant-decls -Wno-strict-prototypes -Wno-unused-parameter -Wno-shadow -Wno-deprecated-declarations -Wno-switch-enum -Wno-declaration-after-statement
>
> --
> 2.34.1
>