Public issue detail

Runaway CPU investigation for sshd-auth: unknown userspace loop at __tcp_transmit_skb

sshd-auth is stuck in a likely unclassified userspace loop: 50.00% of sampled CPU passed through __tcp_transmit_skb, with repeated restart_syscall x1.

highpackage: openssh-serversource: opensshscore: 106reports: 1successful triage

Last seen: 2026-06-22 16:24 UTC. Public JSON: /v1/issues/019e4974-82e3-7921-a12b-9341e67cadf3

Successful triage

Fixer did not find an honest diff-backed change in this source tree. Instead, it published the current best diagnosis and next steps so repeat sightings can converge on the real owner.

best triagecreated: 2026-05-21 09:21 UTCvalidation: ready

sshd-auth likely remains stuck in an unclassified userspace loop. Fixer produced a diagnosis report and intentionally skipped an automatic package patch attempt because the evidence is not specific enough to choose a safe source change.

Likely owner

external dependency or workload outside the current source tree

Reason: weak-unknown-runaway-evidence

Next steps

  • Confirm the hotspot still points at external dependency or workload outside the current source tree with a fresh perf sample before filing the bug.
  • Capture the actual hot backend or child process rather than the parent service wrapper if the issue recurs.
  • Map external dependency or workload outside the current source tree to its owning package or project and file an upstream or distro bug with the summarized evidence.
  • If the owner is still unclear, collect another short strace plus `/proc/<pid>/maps` at the moment of the spike.
Browse successful triage

Technical snapshot

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

Representative thread backtrace

  • Command: sshd-auth: root [net]
  • 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.
  • Wait site: hrtimer_nanosleep
  • Hot path: __tcp_transmit_skb (50.00% sampled CPU)
  • Repeated loop: restart_syscall
  • Top syscalls: restart_syscall x1
  • Package: openssh-server 1:10.3p1-1
  • Kernel: 6.17.10+deb14-amd64
  • Distribution: debian
hrtimer_nanosleep
common_nsleep
__x64_sys_clock_nanosleep
do_syscall_64
entry_SYSCALL_64_after_hwframe

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 sshd-auth: unknown userspace loop at schedule_timeout

possible duplicate

sshd-auth is stuck in a likely unclassified userspace loop: 50.00% of sampled CPU passed through schedule_timeout, with repeated restart_syscall x1.

highpackage: openssh-serversource: opensshscore: 106reports: 1similarity: 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: 2026-07-02 22:27 UTC. Public page: /issues/019f0e0a-9b12-7bc3-ba1f-6777e4555f8d. Public JSON: /v1/issues/019f0e0a-9b12-7bc3-ba1f-6777e4555f8d

Runaway CPU investigation for sshd-auth: unknown userspace loop at fdget_pos

possible duplicate

sshd-auth is stuck in a likely unclassified userspace loop: 50.00% of sampled CPU passed through fdget_pos, with repeated no dominant syscall sample was captured.

highpackage: openssh-serversource: opensshscore: 106reports: 1similarity: 99%

Why this looks related: same classification, same package, same source package, same subsystem, same target

Last seen: 2026-06-27 21:56 UTC. Public page: /issues/019f0a5d-c564-7ca1-bf39-b796c2e8376d. Public JSON: /v1/issues/019f0a5d-c564-7ca1-bf39-b796c2e8376d

Runaway CPU investigation for sshd-auth: unknown userspace loop at __free_one_page

possible duplicate

sshd-auth is stuck in a likely unclassified userspace loop: 59.36% of sampled CPU passed through __free_one_page, with repeated restart_syscall x1.

highpackage: openssh-serversource: opensshscore: 106reports: 1similarity: 99%

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

Last seen: 2026-06-27 18:17 UTC. Public page: /issues/019f056b-3317-7523-ae06-871756bd6b92. Public JSON: /v1/issues/019f056b-3317-7523-ae06-871756bd6b92

Runaway CPU investigation for sshd-session: unknown userspace loop at sock_poll

possible duplicate

sshd-session is stuck in a likely unclassified userspace loop: 100.00% of sampled CPU passed through sock_poll, with repeated thread backtraces show 1 thread(s) around 0x00007f35fa09a7d2 in ?? () from target:<path>.

highpackage: openssh-serversource: opensshscore: 106reports: 2patch attempt readysimilarity: 88%

Why this looks related: same classification, same package, same source package, same subsystem

Last seen: 2026-06-27 17:58 UTC. Public page: /issues/019dff15-4a95-7fb3-b680-40595c35ee68. Public JSON: /v1/issues/019dff15-4a95-7fb3-b680-40595c35ee68

Runaway CPU investigation for sshd-session: unknown userspace loop at getuid@plt

possible duplicate

sshd-session is stuck in a likely unclassified userspace loop: 12.29% of sampled CPU passed through getuid@plt, with repeated thread backtraces show 1 thread(s) around 0x00007f4a7a09a7d2 in ?? () from target:<path>.

highpackage: openssh-serversource: opensshscore: 106reports: 1similarity: 85%

Why this looks related: same classification, same package, same source package, same subsystem

Last seen: 2026-07-01 21:48 UTC. Public page: /issues/019f0b26-eab5-72b2-b263-744003837417. Public JSON: /v1/issues/019f0b26-eab5-72b2-b263-744003837417

Runaway CPU investigation for sshd-session: unknown userspace loop at uncharge_folio

possible duplicate

sshd-session is stuck in a likely unclassified userspace loop: 28.29% of sampled CPU passed through uncharge_folio, with repeated thread backtraces show 1 thread(s) around 0x00007f57f0c9a7d2 in ?? () from target:<path>.

highpackage: openssh-serversource: opensshscore: 106reports: 1similarity: 84%

Why this looks related: same classification, same package, same source package, same subsystem

Last seen: 2026-07-02 22:27 UTC. Public page: /issues/019f20e6-c120-7931-9e82-74a4401b64d9. Public JSON: /v1/issues/019f20e6-c120-7931-9e82-74a4401b64d9

Worker outcome summary

This issue has 1 recorded worker attempt. Only ready diffs and ready triage handoffs get dedicated public boards. Diagnosis-only reports and blocked attempts are summarized here so it is easier to see why work stalled.

1 ready triage handoffs

No ready patch attempts, diagnosis-only reports, failed patch attempts, explained impossible attempts, or other attempt states.

Most common blockers

  • weak-unknown-runaway-evidence (1 attempt)

Published attempts

ready triage handoff

triage

sshd-auth likely remains stuck in an unclassified userspace loop. Fixer produced a diagnosis report and intentionally skipped an automatic package patch attempt because the evidence is not specific enough to choose a safe source change.

state: readycreated: 2026-05-21 09:21 UTCvalidation: ready

Why it stopped

weak-unknown-runaway-evidence

Handoff

Likely owner: external dependency or workload outside the current source tree

Reason: weak-unknown-runaway-evidence

  • Confirm the hotspot still points at external dependency or workload outside the current source tree with a fresh perf sample before filing the bug.
  • Capture the actual hot backend or child process rather than the parent service wrapper if the issue recurs.
  • Map external dependency or workload outside the current source tree to its owning package or project and file an upstream or distro bug with the summarized evidence.
  • If the owner is still unclear, collect another short strace plus `/proc/<pid>/maps` at the moment of the spike.

Quarantine stays on by default so the public queue is harder to spam.