https://github.com/python/cpython/commit/a17301ab3d04a3ebf79ffac754570294d9025023
commit: a17301ab3d04a3ebf79ffac754570294d9025023
branch: main
author: flow <[email protected]>
committer: pablogsal <[email protected]>
date: 2026-03-22T18:53:00Z
summary:
gh-135953: Properly obtain main thread identifier in Gecko Collector (#146045)
files:
A Misc/NEWS.d/next/Tools-Demos/2026-03-22-00-00-00.gh-issue-135953.IptOwg.rst
M Lib/profiling/sampling/constants.py
M Lib/profiling/sampling/gecko_collector.py
M Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
M Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
M Modules/_remote_debugging/_remote_debugging.h
M Modules/_remote_debugging/module.c
M Modules/_remote_debugging/threads.c
diff --git a/Lib/profiling/sampling/constants.py
b/Lib/profiling/sampling/constants.py
index 58a57700fbdd4a..a364d0b8fde1e0 100644
--- a/Lib/profiling/sampling/constants.py
+++ b/Lib/profiling/sampling/constants.py
@@ -37,6 +37,7 @@
THREAD_STATUS_UNKNOWN,
THREAD_STATUS_GIL_REQUESTED,
THREAD_STATUS_HAS_EXCEPTION,
+ THREAD_STATUS_MAIN_THREAD,
)
except ImportError:
# Fallback for tests or when module is not available
@@ -45,3 +46,4 @@
THREAD_STATUS_UNKNOWN = (1 << 2)
THREAD_STATUS_GIL_REQUESTED = (1 << 3)
THREAD_STATUS_HAS_EXCEPTION = (1 << 4)
+ THREAD_STATUS_MAIN_THREAD = (1 << 5)
diff --git a/Lib/profiling/sampling/gecko_collector.py
b/Lib/profiling/sampling/gecko_collector.py
index 28ef9b69bf7968..8986194268b3ce 100644
--- a/Lib/profiling/sampling/gecko_collector.py
+++ b/Lib/profiling/sampling/gecko_collector.py
@@ -9,7 +9,7 @@
from .collector import Collector, filter_internal_frames
from .opcode_utils import get_opcode_info, format_opcode
try:
- from _remote_debugging import THREAD_STATUS_HAS_GIL, THREAD_STATUS_ON_CPU,
THREAD_STATUS_UNKNOWN, THREAD_STATUS_GIL_REQUESTED, THREAD_STATUS_HAS_EXCEPTION
+ from _remote_debugging import THREAD_STATUS_HAS_GIL, THREAD_STATUS_ON_CPU,
THREAD_STATUS_UNKNOWN, THREAD_STATUS_GIL_REQUESTED,
THREAD_STATUS_HAS_EXCEPTION, THREAD_STATUS_MAIN_THREAD
except ImportError:
# Fallback if module not available (shouldn't happen in normal use)
THREAD_STATUS_HAS_GIL = (1 << 0)
@@ -17,6 +17,7 @@
THREAD_STATUS_UNKNOWN = (1 << 2)
THREAD_STATUS_GIL_REQUESTED = (1 << 3)
THREAD_STATUS_HAS_EXCEPTION = (1 << 4)
+ THREAD_STATUS_MAIN_THREAD = (1 << 5)
# Categories matching Firefox Profiler expectations
@@ -174,15 +175,16 @@ def collect(self, stack_frames, timestamps_us=None):
for thread_info in interpreter_info.threads:
frames = filter_internal_frames(thread_info.frame_info)
tid = thread_info.thread_id
+ status_flags = thread_info.status
+ is_main_thread = bool(status_flags & THREAD_STATUS_MAIN_THREAD)
# Initialize thread if needed
if tid not in self.threads:
- self.threads[tid] = self._create_thread(tid)
+ self.threads[tid] = self._create_thread(tid,
is_main_thread)
thread_data = self.threads[tid]
# Decode status flags
- status_flags = thread_info.status
has_gil = bool(status_flags & THREAD_STATUS_HAS_GIL)
on_cpu = bool(status_flags & THREAD_STATUS_ON_CPU)
gil_requested = bool(status_flags &
THREAD_STATUS_GIL_REQUESTED)
@@ -288,18 +290,12 @@ def collect(self, stack_frames, timestamps_us=None):
self.sample_count += len(times)
- def _create_thread(self, tid):
+ def _create_thread(self, tid, is_main_thread):
"""Create a new thread structure with processed profile format."""
- # Determine if this is the main thread
- try:
- is_main = tid == threading.main_thread().ident
- except (RuntimeError, AttributeError):
- is_main = False
-
thread = {
"name": f"Thread-{tid}",
- "isMainThread": is_main,
+ "isMainThread": is_main_thread,
"processStartupTime": 0,
"processShutdownTime": None,
"registerTime": 0,
diff --git
a/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
b/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
index 033a533fe5444e..29f83c843561cd 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
@@ -18,9 +18,11 @@
THREAD_STATUS_UNKNOWN,
THREAD_STATUS_GIL_REQUESTED,
THREAD_STATUS_HAS_EXCEPTION,
+ THREAD_STATUS_MAIN_THREAD,
)
from profiling.sampling.binary_collector import BinaryCollector
from profiling.sampling.binary_reader import BinaryReader
+ from profiling.sampling.gecko_collector import GeckoCollector
ZSTD_AVAILABLE = _remote_debugging.zstd_available()
except ImportError:
@@ -318,6 +320,7 @@ def test_status_flags_preserved(self):
THREAD_STATUS_UNKNOWN,
THREAD_STATUS_GIL_REQUESTED,
THREAD_STATUS_HAS_EXCEPTION,
+ THREAD_STATUS_MAIN_THREAD,
THREAD_STATUS_HAS_GIL | THREAD_STATUS_ON_CPU,
THREAD_STATUS_HAS_GIL | THREAD_STATUS_HAS_EXCEPTION,
THREAD_STATUS_HAS_GIL
@@ -342,6 +345,35 @@ def test_status_flags_preserved(self):
self.assertEqual(count, len(statuses))
self.assert_samples_equal(samples, collector)
+ def test_binary_replay_preserves_main_thread_for_gecko(self):
+ """Binary replay preserves main thread identity for GeckoCollector."""
+ samples = [
+ [
+ make_interpreter(
+ 0,
+ [
+ make_thread(
+ 1,
+ [make_frame("main.py", 10, "main")],
+ THREAD_STATUS_MAIN_THREAD,
+ ),
+ make_thread(2, [make_frame("worker.py", 20,
"worker")]),
+ ],
+ )
+ ]
+ ]
+ filename = self.create_binary_file(samples)
+ collector = GeckoCollector(1000)
+
+ with BinaryReader(filename) as reader:
+ count = reader.replay_samples(collector)
+
+ self.assertEqual(count, 2)
+ profile = collector._build_profile()
+ threads = {thread["tid"]: thread for thread in profile["threads"]}
+ self.assertTrue(threads[1]["isMainThread"])
+ self.assertFalse(threads[2]["isMainThread"])
+
def test_multiple_threads_per_sample(self):
"""Multiple threads in one sample roundtrip exactly."""
threads = [
diff --git a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
index 8e6afa91e89daf..06c9e51e0c9c55 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
@@ -28,6 +28,7 @@
THREAD_STATUS_HAS_GIL,
THREAD_STATUS_ON_CPU,
THREAD_STATUS_GIL_REQUESTED,
+ THREAD_STATUS_MAIN_THREAD,
)
except ImportError:
raise unittest.SkipTest(
@@ -524,6 +525,7 @@ def test_gecko_collector_basic(self):
MockThreadInfo(
1,
[MockFrameInfo("file.py", 10, "func1"),
MockFrameInfo("file.py", 20, "func2")],
+ status=THREAD_STATUS_MAIN_THREAD,
)
],
)
@@ -556,6 +558,7 @@ def test_gecko_collector_basic(self):
threads = profile_data["threads"]
self.assertEqual(len(threads), 1)
thread_data = threads[0]
+ self.assertTrue(thread_data["isMainThread"])
# Verify thread structure
self.assertIn("samples", thread_data)
diff --git
a/Misc/NEWS.d/next/Tools-Demos/2026-03-22-00-00-00.gh-issue-135953.IptOwg.rst
b/Misc/NEWS.d/next/Tools-Demos/2026-03-22-00-00-00.gh-issue-135953.IptOwg.rst
new file mode 100644
index 00000000000000..50f39a830de1b1
--- /dev/null
+++
b/Misc/NEWS.d/next/Tools-Demos/2026-03-22-00-00-00.gh-issue-135953.IptOwg.rst
@@ -0,0 +1,3 @@
+Properly identify the main thread in the Gecko profiler collector by
+using a status flag from the interpreter state instead of relying on
+:func:`threading.main_thread` in the collector process.
diff --git a/Modules/_remote_debugging/_remote_debugging.h
b/Modules/_remote_debugging/_remote_debugging.h
index 7bcb2f483234ec..570f6b23b75849 100644
--- a/Modules/_remote_debugging/_remote_debugging.h
+++ b/Modules/_remote_debugging/_remote_debugging.h
@@ -172,6 +172,7 @@ typedef enum _WIN32_THREADSTATE {
#define THREAD_STATUS_UNKNOWN (1 << 2)
#define THREAD_STATUS_GIL_REQUESTED (1 << 3)
#define THREAD_STATUS_HAS_EXCEPTION (1 << 4)
+#define THREAD_STATUS_MAIN_THREAD (1 << 5)
/* Exception cause macro */
#define set_exception_cause(unwinder, exc_type, message)
\
@@ -575,7 +576,8 @@ extern PyObject* unwind_stack_for_thread(
RemoteUnwinderObject *unwinder,
uintptr_t *current_tstate,
uintptr_t gil_holder_tstate,
- uintptr_t gc_frame
+ uintptr_t gc_frame,
+ uintptr_t main_thread_tstate
);
/* Thread stopping functions (for blocking mode) */
diff --git a/Modules/_remote_debugging/module.c
b/Modules/_remote_debugging/module.c
index 040bd3db377315..4f294b80ba0739 100644
--- a/Modules/_remote_debugging/module.c
+++ b/Modules/_remote_debugging/module.c
@@ -583,11 +583,16 @@
_remote_debugging_RemoteUnwinder_get_stack_trace_impl(RemoteUnwinderObject *self
current_tstate = self->tstate_addr;
}
+ // Acquire main thread state information
+ uintptr_t main_thread_tstate = GET_MEMBER(uintptr_t,
interp_state_buffer,
+ self->debug_offsets.interpreter_state.threads_main);
+
while (current_tstate != 0) {
uintptr_t prev_tstate = current_tstate;
PyObject* frame_info = unwind_stack_for_thread(self,
¤t_tstate,
gil_holder_tstate,
- gc_frame);
+ gc_frame,
+ main_thread_tstate);
if (!frame_info) {
// Check if this was an intentional skip due to mode-based
filtering
if ((self->mode == PROFILING_MODE_CPU || self->mode ==
PROFILING_MODE_GIL ||
@@ -1207,6 +1212,9 @@ _remote_debugging_exec(PyObject *m)
if (PyModule_AddIntConstant(m, "THREAD_STATUS_HAS_EXCEPTION",
THREAD_STATUS_HAS_EXCEPTION) < 0) {
return -1;
}
+ if (PyModule_AddIntConstant(m, "THREAD_STATUS_MAIN_THREAD",
THREAD_STATUS_MAIN_THREAD) < 0) {
+ return -1;
+ }
if (RemoteDebugging_InitState(st) < 0) {
return -1;
diff --git a/Modules/_remote_debugging/threads.c
b/Modules/_remote_debugging/threads.c
index 3100b83c8f4899..527957c6fef067 100644
--- a/Modules/_remote_debugging/threads.c
+++ b/Modules/_remote_debugging/threads.c
@@ -291,7 +291,8 @@ unwind_stack_for_thread(
RemoteUnwinderObject *unwinder,
uintptr_t *current_tstate,
uintptr_t gil_holder_tstate,
- uintptr_t gc_frame
+ uintptr_t gc_frame,
+ uintptr_t main_thread_tstate
) {
PyObject *frame_info = NULL;
PyObject *thread_id = NULL;
@@ -395,6 +396,10 @@ unwind_stack_for_thread(
status_flags |= THREAD_STATUS_ON_CPU;
}
+ if (*current_tstate == main_thread_tstate) {
+ status_flags |= THREAD_STATUS_MAIN_THREAD;
+ }
+
// Check if we should skip this thread based on mode
int should_skip = 0;
if (unwinder->skip_non_matching_threads) {
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