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GeezerVison is showing github.com — gh-156545: Fix flamegraph export RecursionError on deeply recursive programs by tonghuaroot · Pull Request #156546 · python/cpython

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@tonghuaroot

@tonghuaroot tonghuaroot commented Aug 29, 2026 •
edited by bedevere-app Bot
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Flamegraph export raises RecursionError when sampled stacks exceed the usual Python recursion limit. Temporarily allow enough recursion for the unwinder's 1,536-frame maximum during export, restoring the original limit in finally.

Tests cover a full 1,536-frame export and limit restoration after success, empty output, and an export error. The profiling test suite passes.

Closes #156545.

  • Issue: profiling: flamegraph export fails with RecursionError on a deeply recursive program #156545

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@tonghuaroot
pythongh-156545: Fix flamegraph export RecursionError on deeply recur…
23f5f75
…sive programs
@tonghuaroot
tonghuaroot requested a review from pablogsal as a code owner August 29, 2026 03:41
@bedevere-app bedevere-app Bot added the awaiting review label Aug 29, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Aug 29, 2026
profiling: flamegraph export fails with RecursionError on a deeply recursive program #156545
Closed
tonghuaroot and others added 3 commits August 29, 2026 11:44
@tonghuaroot
Tighten comments
a1ad4cd
@pablogsal
Merge remote-tracking branch 'upstream/main' into tachyon-land-156546
68dd928
@pablogsal
pythongh-156545: Verify recursion limit restoration during export
a3f2ee8
@pablogsal pablogsal added the needs backport to 3.15 bugs and security fixes label Oct 5, 2026
@pablogsal
pablogsal enabled auto-merge (squash) October 5, 2026 14:06
pablogsal
pablogsal approved these changes Oct 5, 2026
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Oct 5, 2026
@pablogsal pablogsal removed the needs backport to 3.15 bugs and security fixes label Oct 5, 2026
@pablogsal pablogsal mentioned this pull request Oct 5, 2026
[3.15] gh-156545: Fix flamegraph export RecursionError on deeply recursive programs (GH-156546) #158851
Merged
@bedevere-app

bedevere-app Bot commented Oct 5, 2026

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GH-158851 is a backport of this pull request to the 3.15 branch.

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@pablogsal
pablogsal merged commit 1441e51 into python:main Oct 5, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label Oct 5, 2026
pablogsal added a commit that referenced this pull request Oct 5, 2026
@pablogsal @tonghuaroot
[3.15] gh-156545: Fix flamegraph export RecursionError on deeply recu…
0ac7217
…rsive programs (GH-156546) (#158851)

Backport of GH-156546.

Co-authored-by: tonghuaroot (童话) <[email protected]>
pablogsal added a commit to pablogsal/cpython that referenced this pull request Oct 5, 2026
@pablogsal
Revert "[3.15] pythongh-156545: Fix flamegraph export RecursionError …
ebe784e
…on deeply recursive programs (pythonGH-156546) (python#158851)"

This reverts commit 0ac7217.
pablogsal added a commit that referenced this pull request Oct 11, 2026
@pablogsal @miss-islington
@maurycy @claude @vstinner @StanFromIreland @tonghuaroot @hetaozdh @edvilme @deadlovelll
[3.15] Restore deferred backports for 3.15.1, including GH-158874 (#1…
4ceb3fa
…58882)

* [3.15] gh-153364: Make frame, coroutine, and task-waiter chain walks iterative and bounded (GH-153365) (#158813)

gh-153364: Make frame, coroutine, and task-waiter chain walks iterative and bounded (GH-153365)

* let me declare single limit

* use our new limit in process_frame_chain()

* add it in parse_async_frame_chain()

* parse_coro_chain()

* NEWS

* async in the message?

* test

* no race

* process_task_awaited_by

* process_task_awaited_by limit test

* NEWS

* MAX_TASK_WAITER_CHAIN_DEPTH

* TASK_WAITER_CHAIN_DEPTH in test

* TASK_WAITER_CHAIN_DEPTH 256

* prevent the drift with the comment

* better naming, better style

* MAX_TASK_WAITER_CHAIN_DEPTH comment

* task-waiter iterative bfs walk

* iterative coro-walk

* nicer news

* 1 << 14

* comment

* unused read_Py_ssize_t

* fix tombstones

* simplify

* correct msg

* better test

* news for tombstones

* left-over from when testing buggy version

* redundant new line
(cherry picked from commit e0861c6)

Co-authored-by: Maurycy Pawłowski-Wieroński <[email protected]>
(cherry picked from commit 9e401cf)

* [3.15] gh-155811: Add a seqcount to `gc_stats` to prevent torn reads (GH-155828) (#158829)

* update_seq

* no need for XCHGL, MOVL is enough?

* gh-155811: Retry an inconsistent GC snapshot once

---------
(cherry picked from commit 5fecd44)

Co-authored-by: Pablo Galindo Salgado <[email protected]>
Co-authored-by: Claude Fable 5.1 <[email protected]>
(cherry picked from commit 0281240)

* [3.15] gh-151292: `_remote_debugging`: Do not corrupt the binary file when hitting `OverflowError` (GH-152892) (#158830)

gh-151292: `_remote_debugging`: Do not corrupt the binary file when hitting `OverflowError` (GH-152892)

* the kolektor

* test

* better test

* news

* =Q, move const to the base, not self.running

* gh-151292: Track binary writer finalization state

---------
(cherry picked from commit f839c06)

Co-authored-by: Maurycy Pawłowski-Wieroński <[email protected]>
Co-authored-by: Pablo Galindo Salgado <[email protected]>
(cherry picked from commit 8a7c23f)

* [3.15] gh-158583: Fix uninitialized memory read in bytes.fromhex() (GH-158584) (#158691)

gh-158583: Fix uninitialized memory read in bytes.fromhex() (GH-158584)
(cherry picked from commit 9d22a53)

Co-authored-by: Victor Stinner <[email protected]>
(cherry picked from commit 4f7af46)

* [3.15] gh-154194: Degrade frames in Tachyon instead of failing the sample (GH-154195) (#158831)

* gh-154194: Degrade frames in Tachyon instead of failing the sample (#154195)

* degrade gracefully

* news

* better NEWS wording

* do not raise on MAX_REMOTE_STR_READ

* bye MAX_REMOTE_STR_READ

* fix -m asyncio ps|pstree

* test truncation and linetable sentinel

* simpler

* simpler

* redundant now

* respect #157790 in the news

---------

Co-authored-by: Pablo Galindo Salgado <[email protected]>
(cherry picked from commit 7d25916)

* Preserve the stable ABI when creating fallback frame names

---------

Co-authored-by: Maurycy Pawłowski-Wieroński <[email protected]>
(cherry picked from commit c27f494)

* [3.15] Add MSan to CI (GH-158625) (#158832)

Run a job that the test suite with MSan to the CI (#158625)

* Run the test suite with MSan in CI

* Additional fixes

* Add `_Py_MSAN_UNPOISON_STRING`

* Apply Victor's suggestions

* Apply Victor's suggestions

---------

(cherry picked from commit b93fb19)

Co-authored-by: Stan Ulbrych <[email protected]>
Co-authored-by: Victor Stinner <[email protected]>
(cherry picked from commit 1bc78de)

* [3.15] gh-156810: Write the profiler's collapsed-stack export as UTF-8 (GH-156811) (#156814)

gh-156810: Write the profiler's collapsed-stack export as UTF-8 (GH-156811)
(cherry picked from commit c3706f4)

Co-authored-by: tonghuaroot (童话) <[email protected]>
(cherry picked from commit fce28da)

* [3.15] gh-158552: Wait for Windows threads to suspend before blocking sampling (GH-158802) (#158845)

gh-158552: Wait for Windows threads to suspend before blocking sampling (GH-158802)

* gh-158552: Wait for Windows threads to suspend before blocking sampling

* Use a named Windows thread enumeration status constant
(cherry picked from commit 1643525)

Co-authored-by: Pablo Galindo Salgado <[email protected]>
(cherry picked from commit 31288da)

* [3.15] gh-152721: Fix quadratic RLE replay time in the profiling binary reader (GH-152722) (#158850)

Backport of GH-152722.

Co-authored-by: tonghuaroot <[email protected]>
(cherry picked from commit ebaca2a)

* [3.15] gh-156545: Fix flamegraph export RecursionError on deeply recursive programs (GH-156546) (#158851)

Backport of GH-156546.

Co-authored-by: tonghuaroot (童话) <[email protected]>
(cherry picked from commit 0ac7217)

* [3.15] gh-158540: Add the profiled script's directory to sys.path (GH-158548) (#158844)

gh-158540: Add the profiled script's directory to sys.path (GH-158548)

* gh-158540: Add the profiled script's directory to sys.path

When a script is profiled with ``python -m profiling.sampling run
script.py`` from another directory, the script cannot import modules
placed next to it, because ``_sync_coordinator._execute_script()``
executes it with the working directory (added by
``_setup_environment()`` for the module case) as ``sys.path[0]``
instead of the script's own directory.

Make the script's directory importable in ``_execute_script()``,
matching the behavior of ``python script.py``.

Add a regression test that runs the coordinator on a script importing
a sibling module.

* Update _sync_coordinator.py Comment simplified

* gh-158540: Resolve symlinks when adding the script directory to sys.path

``python script.py`` resolves symlinks when computing ``sys.path[0]``, so
a script reached through a symlink (``link.py -> sub/where.py``) imports
modules from the real script's directory.  Apply ``os.path.realpath()``
before taking the directory name, and make sure the result is placed at
the front of ``sys.path`` even if it was already listed.

Add a regression test for a symlinked script.

---------
(cherry picked from commit 3f02aab)

Co-authored-by: he_tao <[email protected]>
Co-authored-by: Eduardo Villalpando Mello <[email protected]>
(cherry picked from commit f52d831)

* [3.15] gh-153838: Skip non-regular source files in the heatmap exporter (GH-153839) (#158853)

Backport of GH-153839.

Co-authored-by: tonghuaroot <[email protected]>
(cherry picked from commit 48998df)

* [3.15] gh-158539: Fix exception mode missing handlers in generators/coroutines (GH-158581) (#158852)

* [3.15] gh-158539: Fix exception mode missing handlers in generators/coroutines (GH-158581)

Backport of GH-158581.

Co-authored-by: LucasZhou <[email protected]>

* [3.15] gh-158539: Use portable static assertion messages

* [3.15] gh-158539: Keep layout assertions with debug-offset validation

* [3.15] gh-158539: Use the platform guard for in-process inspection tests

---------

Co-authored-by: LucasZhou <[email protected]>
(cherry picked from commit d625ecb)

* [3.15] gh-158522: Fix truncated stack for a task whose coroutine recurses (GH-158526) (#158870)

Co-authored-by: Timofei Ivankov <[email protected]>
(cherry picked from commit a904b39)

* gh-156545, gh-158539: Fix deep flamegraph export on small C stacks and macOS runtime lookup (#158874)

(cherry picked from commit 114de19)

Include the C-stack test helper from main, introduced by
ce5ae29, which the regression test
requires but 3.15 does not yet provide.

---------

Co-authored-by: Miss Islington (bot) <[email protected]>
Co-authored-by: Maurycy Pawłowski-Wieroński <[email protected]>
Co-authored-by: Claude Fable 5.1 <[email protected]>
Co-authored-by: Victor Stinner <[email protected]>
Co-authored-by: Stan Ulbrych <[email protected]>
Co-authored-by: Victor Stinner <[email protected]>
Co-authored-by: tonghuaroot (童话) <[email protected]>
Co-authored-by: he_tao <[email protected]>
Co-authored-by: Eduardo Villalpando Mello <[email protected]>
Co-authored-by: LucasZhou <[email protected]>
Co-authored-by: Timofei Ivankov <[email protected]>
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