parallel pahole hangs while building modules from nvidia-open-kernel-dkms

[Domenico Andreoli <domenico.andreoli@linux.com>]

Hi,

  This a forward of Debian bug report [0] where you can find more
details. At [1] and [2] you can get the kernel and module to reproduce.
I could reproduce on both amd64 and arm64 using pahole 1.29.

This is marked as serious severity because it makes the autobuilder hang
as well [3].

Could you please help?

Regards,
Domenico


The command to succeed:

This simplified (sequential) command succeeds:

cp nvidia-modeset.base.ko nvidia-modeset.ko
LLVM_OBJCOPY="x86_64-linux-gnu-objcopy" pahole -J --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func,decl_tag_kfuncs --btf_features=distilled_base --btf_base vmlinux nvidia-modeset.ko -j1
echo $?

producing this output:
===== 8< =====
dwarf_expr: unhandled 0x12 DW_OP_ operation
Unsupported DW_TAG_reference_type(0x10): type: 0x28172
Error while encoding BTF.
0
===== >8 =====


While this (parallel) command hangs:

cp nvidia-modeset.base.ko nvidia-modeset.ko
LLVM_OBJCOPY="x86_64-linux-gnu-objcopy" pahole -J --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func,decl_tag_kfuncs --btf_features=distilled_base --btf_base vmlinux nvidia-modeset.ko -j2
echo $?

producing this output:
===== 8< =====
dwarf_expr: unhandled 0x12 DW_OP_ operation
dwarf_expr: unhandled 0x12 DW_OP_ operation
dwarf_expr: unhandled 0x12 DW_OP_ operation
dwarf_expr: unhandled 0x12 DW_OP_ operation
Unsupported DW_TAG_reference_type(0x10): type: 0x28172
Error while encoding BTF.
Terminated
143
===== >8 =====


[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1100503
[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?att=1;bug=1100503;filename=vmlinux.zst;msg=19
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?att=1;bug=1100503;filename=nvidia-modeset.base.ko.zst;msg=12
[3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1101262

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