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gh-151436: Fix missing tstate->last_profiled_frame updates#151437

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python:mainfrom
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gh-151436: Fix missing tstate->last_profiled_frame updates#151437
maurycy wants to merge 2 commits into
python:mainfrom
maurycy:gh-151436

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@maurycy

@maurycy maurycy commented Jun 13, 2026 •
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Please see #151436 for more details.

The issue is fixed, drv_a is back:

def gen():
    while True:
        n = yield
        sum(range(n))

g = gen()
next(g)

def drv_a(): g.send(500)
def drv_b(): g.send(50000)

while True:
    drv_a(); drv_b()
2026-06-13T11:47:41.099330000+0200 maurycy@gimel /Users/maurycy/work/cpython (gh-151436 4eab5a0?) % sudo ./python.exe -m profiling.sampling run --collapsed -o /tmp/stacks.txt -d  10 genrepro.py&& cat /tmp/stacks.txt
Captured 10,000 samples in 10.00 seconds
Sample rate: 999.99 samples/sec
Error rate: 0.01
Collapsed stack output written to /tmp/stacks.txt
tid:13799271;<frozen runpy>:_run_module_as_main:201;<frozen runpy>:_run_code:87;genrepro.py:<module>:13;genrepro.py:drv_b:10;genrepro.py:gen:4 9945
tid:13799271;<frozen runpy>:_run_module_as_main:201;<frozen runpy>:_run_code:87;genrepro.py:<module>:13;genrepro.py:drv_a:9;genrepro.py:gen:4 48
tid:13799271;<frozen runpy>:_run_module_as_main:201;<frozen runpy>:_run_code:87;genrepro.py:<module>:13;genrepro.py:drv_b:10;genrepro.py:gen:3 3
tid:13799271;<frozen runpy>:_run_module_as_main:201;<frozen runpy>:_run_code:87;genrepro.py:<module>:13 1
tid:13799271;<frozen runpy>:_run_module_as_main:201;<frozen runpy>:_run_code:87;genrepro.py:<module>:13;genrepro.py:drv_a:9 1
tid:13799271;<frozen runpy>:_run_module_as_main:201;<frozen runpy>:_run_code:87;genrepro.py:<module>:13;genrepro.py:drv_b:10 1
2026-06-13T11:47:51.429974000+0200 maurycy@gimel /Users/maurycy/work/cpython (gh-151436 4eab5a0?) %

0,5% (48/9996 = 0,48%) is roughly correct, since it shouldn't be exactly linear.

I can try to come up with reproduction for each miss.

Should it be a helper?

If you ask me, the whole mechanism smells me of ABA...

@bedevere-app bedevere-app Bot mentioned this pull request Jun 13, 2026
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@maurycy maurycy marked this pull request as ready for review June 13, 2026 09:58
@maurycy maurycy requested a review from markshannon as a code owner June 13, 2026 09:58
@maurycy

maurycy commented Jun 13, 2026

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cc @pablogsal @savannahostrowski

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@markshannon markshannon Awaiting requested review from markshannon markshannon is a code owner

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