On Thu, Aug 28, 2025 at 3:32 PM Joe Lawrence [off-list ref] wrote:

On 8/26/25 5:54 AM, Jan Stancek wrote:

quoted

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@redhat.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@redhat.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@redhat.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