Public issue detail

Runaway CPU investigation for postgres: unknown userspace loop at ModifyWaitEvent

postgres is stuck in a likely unclassified userspace loop: 100.00% of sampled CPU passed through ModifyWaitEvent, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 1

Last seen: 2026-06-05 01:39 UTC. Public JSON: /v1/issues/019e953c-870f-71b2-9fcf-1504b573af7d

Technical snapshot

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

Representative thread backtrace

  • Command: /usr/lib/postgresql/18/bin/postgres -D /var/lib/postgresql/18/main -c config_file=/etc/postgresql/18/main/postgresql.conf
  • 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 0x00007f322d29a7d2 in ?? () from target:<path>
  • Contention signals: event-loop-wakeups, gdb-stderr: gdb: warning: Couldn't determine a path for the index cache directory. warning: .dynamic section for "target:<path>++.so.6" is not at the expected address (wrong library or version mismatch?)
  • Repeated loop: read -> read -> read
  • Top syscalls: read x54, close x12, rt_sigaction x11, openat x9
  • Package: postgresql-18 18.3-1.pgdg+2
  • Kernel: 6.17.10+deb14-amd64
  • Distribution: debian
0x00007f322d29a7d2 in ?? () from target:<path>
0x00007f322d29a7ed in ?? () from target:<path>
0x00007f322d31d0cd in epoll_wait () from target:<path>
0x00005574dfc994fa in WaitEventSetWait ()
0x00005574dfc02498 in ?? ()
0x00005574dfc04e45 in PostmasterMain ()
0x00005574df8a335a in main ()

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 postgres: unknown userspace loop at filemap_map_pages

possible duplicate

postgres is stuck in a likely unclassified userspace loop: 10.71% of sampled CPU passed through filemap_map_pages, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 2similarity: 99%

Why this looks related: same classification, same package, same source package, same subsystem, same target, same wait site, very similar public summary

Last seen: 2026-06-09 02:17 UTC. Public page: /issues/019e2441-6693-7693-877d-91f13bbf36ea. Public JSON: /v1/issues/019e2441-6693-7693-877d-91f13bbf36ea

Runaway CPU investigation for postgres: unknown userspace loop at next_uptodate_folio

possible duplicate

postgres is stuck in a likely unclassified userspace loop: 13.90% of sampled CPU passed through next_uptodate_folio, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 2similarity: 99%

Why this looks related: same classification, same package, same source package, same subsystem, same target, same wait site, very similar public summary

Last seen: 2026-06-06 04:41 UTC. Public page: /issues/019dcfd5-049e-7413-b236-3e76a8fcb568. Public JSON: /v1/issues/019dcfd5-049e-7413-b236-3e76a8fcb568

Runaway CPU investigation for postgres: busy poll at WaitEventSetWait

possible duplicate

postgres is stuck in a likely busy poll loop: 40.57% of sampled CPU passed through WaitEventSetWait, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 1similarity: 98%

Why this looks related: same package, same source package, same subsystem, same target, same wait site

Last seen: 2026-06-03 14:33 UTC. Public page: /issues/019e8dbf-85f6-7f12-bf9b-bf849bd9a7bf. Public JSON: /v1/issues/019e8dbf-85f6-7f12-bf9b-bf849bd9a7bf

Runaway CPU investigation for postgres: busy poll at mas_walk

possible duplicate

postgres is stuck in a likely busy poll loop: 11.56% of sampled CPU passed through mas_walk, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 2similarity: 92%

Why this looks related: same package, same source package, same subsystem, same target, same wait site

Last seen: 2026-06-03 13:31 UTC. Public page: /issues/019d655d-a25d-7e10-8b27-1c78ea0ca744. Public JSON: /v1/issues/019d655d-a25d-7e10-8b27-1c78ea0ca744

Runaway CPU investigation for postgres: busy poll at xas_load

possible duplicate

postgres is stuck in a likely busy poll loop: 8.11% of sampled CPU passed through xas_load, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 2similarity: 92%

Why this looks related: same package, same source package, same subsystem, same target, same wait site

Last seen: 2026-06-08 17:21 UTC. Public page: /issues/019d6abe-50ba-72d0-9747-91d8938e7e78. Public JSON: /v1/issues/019d6abe-50ba-72d0-9747-91d8938e7e78

Runaway CPU investigation for postgres: busy poll at unresolved offset in postgres

possible duplicate

postgres is stuck in a likely busy poll loop: 100.00% of sampled CPU passed through unresolved offset, with repeated thread backtraces show 1 thread(s) around 0x00007f322d29a7d2 in ?? () from target:<path>.

highpackage: postgresql-18source: postgresql-18score: 106reports: 2similarity: 92%

Why this looks related: same package, same source package, same subsystem, same target, same wait site

Last seen: 2026-06-08 15:12 UTC. Public page: /issues/019e1bf3-a08a-7041-9430-cfc88ffa1150. Public JSON: /v1/issues/019e1bf3-a08a-7041-9430-cfc88ffa1150

Published attempts

No public attempts have been published for this issue yet.

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