linux-kernel - Re: [PATCH] powerpc/tools: drop `-o pipefail` in gcc check scripts

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Message-ID: <CAASaF6yOskaXhQzvqz_-fZekYimgbNspi0JfT4TAWL-rB6mMhg@mail.gmail.com>
Date: Wed, 10 Sep 2025 09:30:10 +0200
From: Jan Stancek <jstancek@...hat.com>
To: Joe Lawrence <joe.lawrence@...hat.com>, mpe@...erman.id.au, 
	christophe.leroy@...roup.eu, maddy@...ux.ibm.com, npiggin@...il.com
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/tools: drop `-o pipefail` in gcc check scripts

On Thu, Aug 28, 2025 at 3:32 PM Joe Lawrence <joe.lawrence@...hat.com> wrote:
>
> On 8/26/25 5:54 AM, Jan Stancek wrote:
> > We've been observing rare non-deterministic kconfig failures during
> > olddefconfig, where ARCH_USING_PATCHABLE_FUNCTION_ENTRY was getting
> > disabled and with it number of other config options that depend on it.
> >
> > The reason is that gcc-check-fpatchable-function-entry.sh can fail
> > if `grep -q` (or scripts/dummy-tools/gcc) is fast enough to exit while
> > there is still someone writing on other side of pipe. `pipefail`
> > propagates that error up to kconfig.
> >
> > This can be seen for example with:
> >   # (set -e; set -o pipefail; yes | grep -q y); echo $?
> >   141
> >
> > or by running the actual check script in loop extensively:
> >   ----------------------------- 8< -------------------------------
> >   function kconfig()
> >   {
> >     for i in `seq 1 100`; do
> >       arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh \
> >         ./scripts/dummy-tools/gcc -mlittle-endian \
> >         || { echo "Oops"; exit 1; }
> >     done
> >   }
> >
> >   for ((i=0; i<$(nproc); i++)); do kconfig & done
> >   wait; echo "Done"
> >   ----------------------------- >8 -------------------------------
> >
> > Fixes: 0f71dcfb4aef ("powerpc/ftrace: Add support for -fpatchable-function-entry")
> > Fixes: b71c9ffb1405 ("powerpc: Add arch/powerpc/tools directory")
> > Signed-off-by: Jan Stancek <jstancek@...hat.com>
> > ---
> >  arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh | 1 -
> >  arch/powerpc/tools/gcc-check-mprofile-kernel.sh           | 1 -
> >  2 files changed, 2 deletions(-)
> >
> > diff --git a/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh b/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
> > index 06706903503b..baed467a016b 100755
> > --- a/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
> > +++ b/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
> > @@ -2,7 +2,6 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >
> >  set -e
> > -set -o pipefail
> >
> >  # To debug, uncomment the following line
> >  # set -x
> > diff --git a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
> > index 73e331e7660e..6193b0ed0c77 100755
> > --- a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
> > +++ b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
> > @@ -2,7 +2,6 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >
> >  set -e
> > -set -o pipefail
> >
> >  # To debug, uncomment the following line
> >  # set -x
>
> Acked-by: Joe Lawrence <joe.lawrence@...hat.com>
>
> This bug manifests when automated scripts expect to run a kernel build
> after `make olddefconfig`.  I reported this to Jan when I found that

Right, maybe we can still add that too.

Reported-by: Joe Lawrence <joe.lawrence@...hat.com>

Would anyone else also care to review, please?

Thanks,
Jan

> kpatch-build [1] instances were hanging (expecting to hear from a user
> that would never answer :(
>
> [1] https://github.com/dynup/kpatch/blob/master/kpatch-build/kpatch-build
> --
> Joe
>