Public issue detail

Runaway CPU investigation for lto1: unknown userspace loop at bitmap_set_bit(bitmap_head*, int)

lto1 is stuck in a likely unclassified userspace loop: 2.51% of sampled CPU passed through bitmap_set_bit(bitmap_head*, int), with repeated thread backtraces show 1 thread(s) around 0x000000000162a9f7 in constrain_operands(int, unsigned long) ().

highscore: 106reports: 1

Last seen: 2026-09-30 11:46 UTC. Public JSON: /v1/issues/019fa772-cf3b-7890-82d2-60e7dba39362

Technical snapshot

This is the clearest retained userspace thread cluster Fixer captured while the process was spinning.

Representative thread backtrace

  • Command: /usr/libexec/gcc/x86_64-linux-gnu/14/lto1 -quiet -dumpbase ./postgis-3.7.so.ltrans10.ltrans -mtune=generic -march=x86-64 -g -g -g -O2 -O2 -O2 -O2 -O2 -O2 -Werror=vla -Wimplicit-fallthrough=3 -Wshadow=compatible-local -Wformat-truncation=0 -Wno-stringop-truncation -Werror=implicit-function-declaration -Werror=format-security -Werror -fno-openmp -fno-openacc -fcf-protection=full -fasynchronous-unwind-tables -fno-strict-aliasing -fwrapv -fexcess-precision=standard -fstack-protector-strong -fstack-clash-protection -fcf-protection=full -fno-omit-frame-pointer -fno-math-errno -fno-signed-zeros -fno-semantic-interposition -fPIC -fvisibility=hidden -foffload-options=-l_GCC_m -fvisibility=hidden -foffload-options=-l_GCC_m -fltrans /tmp/cc29mSL8.ltrans10.o -o /tmp/ccCt1xnX.s
  • Why Fixer classified it this way: The process is demonstrably CPU-hot, but the current syscall and symbol sample does not point to a single dominant loop family yet.
  • Thread summary: thread backtraces show 1 thread(s) around 0x000000000162a9f7 in constrain_operands(int, unsigned long) ()
  • Contention signals: gdb-stderr: gdb: warning: Couldn't determine a path for the index cache directory. warning: Target and debugger are in different PID namespaces; thread lists and other data are likely unreliable. Connect to gdbserver inside the container. warning: Expected absolute pathname for libpthread in the inferior, but got target:<path> warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
  • Repeated loop: mmap -> munmap -> mmap
  • Top syscalls: mmap x84, munmap x77, write x28
  • Kernel: 7.1.8+deb14.1-amd64
  • Distribution: debian
0x000000000162a9f7 in constrain_operands(int, unsigned long) ()
0x000000000162a368 in extract_constrain_insn_cached(rtx_insn*) ()
0x0000000001750588 in insn_min_length(rtx_insn*) ()
0x000000000180920d in ?? ()
0x000000000175cc86 in ?? ()
0x00000000013c8431 in execute_one_pass(opt_pass*) ()
0x00000000014255cc in ?? ()
0x00000000014255ed in ?? ()

Possible duplicates

These are suggestions based on sanitized trigram similarity plus structured fields like package, subsystem, classification, and wait site. They are not auto-merged.

Runaway CPU investigation for cc1: unknown userspace loop at bitmap_set_bit(bitmap_head*, int)

possible duplicate

cc1 is stuck in a likely unclassified userspace loop: 2.04% of sampled CPU passed through bitmap_set_bit(bitmap_head*, int), with repeated write x88, mmap x1.

highscore: 106reports: 1similarity: 97%

Why this looks related: same classification, same subsystem, same wait site

Last seen: 2026-10-13 06:02 UTC. Public page: /issues/019fa11d-a82b-79e0-891c-85e9b734e4a0. Public JSON: /v1/issues/019fa11d-a82b-79e0-891c-85e9b734e4a0

Runaway CPU investigation for llama-server: unknown userspace loop at uvm_spin_loop

possible duplicate

llama-server is stuck in a likely unclassified userspace loop: 23.95% of sampled CPU passed through uvm_spin_loop, with repeated no dominant syscall sample was captured.

highscore: 106reports: 1similarity: 71%

Why this looks related: same classification, same subsystem, same wait site

Last seen: 2026-10-22 21:00 UTC. Public page: /issues/01a0b753-7de3-74d2-bfee-879445fd371b. Public JSON: /v1/issues/01a0b753-7de3-74d2-bfee-879445fd371b

Runaway CPU investigation for clang: unknown userspace loop at clang::Lexer::LexTokenInternal(clang::Token&, bool)

possible duplicate

clang is stuck in a likely unclassified userspace loop: 1.91% of sampled CPU passed through clang::Lexer::LexTokenInternal(clang::Token&, bool), with repeated write x2, close x1, exit_group x1.

highscore: 106reports: 1similarity: 67%

Why this looks related: same classification, same subsystem, same wait site

Last seen: 2026-10-20 04:50 UTC. Public page: /issues/019ff123-7d66-7253-bc62-d7ba8c5bd3e8. Public JSON: /v1/issues/019ff123-7d66-7253-bc62-d7ba8c5bd3e8

Runaway CPU investigation for po2xml: unknown userspace loop at unresolved offset in libpcre2-16.so.0.14.0

possible duplicate

po2xml is stuck in a likely unclassified userspace loop: 53.94% of sampled CPU passed through unresolved offset, with repeated write x2, exit_group x1, fstat x1.

highscore: 106reports: 1similarity: 66%

Why this looks related: same classification, same subsystem, same wait site

Last seen: 2026-10-19 03:46 UTC. Public page: /issues/01a0f656-df4b-7fc2-acb4-c03fc6235e66. Public JSON: /v1/issues/01a0f656-df4b-7fc2-acb4-c03fc6235e66

Runaway CPU investigation for xsltproc: file not found retry at xsltFindDocument

possible duplicate

xsltproc is stuck in a likely file not found retry loop: 71.03% of sampled CPU passed through xsltFindDocument, with repeated thread backtraces show 1 thread(s) around 0x00007fc89030a730 in xsltFindDocument () from target:<path>.

highpackage: xsltprocsource: libxsltscore: 106reports: 1similarity: 46%

Why this looks related: same subsystem, same wait site

Last seen: 2026-10-21 04:56 UTC. Public page: /issues/019f76a7-76bc-7333-a696-3d38b95d7023. Public JSON: /v1/issues/019f76a7-76bc-7333-a696-3d38b95d7023

Runaway CPU investigation for pdftex: file not found retry at unresolved offset in libz.so.1.3.1

possible duplicate

pdftex is stuck in a likely file not found retry loop: 16.24% of sampled CPU passed through unresolved offset, with repeated thread backtraces show 1 thread(s) around 0x0000559cf35425aa in ?? ().

highscore: 106reports: 1similarity: 46%

Why this looks related: same subsystem, same wait site

Last seen: 2026-10-02 09:54 UTC. Public page: /issues/019f76fe-e585-7490-a51d-2e41820f45d3. Public JSON: /v1/issues/019f76fe-e585-7490-a51d-2e41820f45d3

Published attempts

No public attempts have been published for this issue yet.

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