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bpo-40010: Optimize signal handling in multithreaded applications#19067

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vstinner merged 1 commit into
python:masterfrom
vstinner:signal_pending_signals
Mar 19, 2020
Merged

bpo-40010: Optimize signal handling in multithreaded applications#19067
vstinner merged 1 commit into
python:masterfrom
vstinner:signal_pending_signals

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@vstinner

@vstinner vstinner commented Mar 19, 2020 •
edited by bedevere-bot
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If a thread gets a signal, the bytecode evaluation loop no longer
tries to handle signals before executing each bytecode instruction,
if the thread must not handle signals.

Previously, it was was done until the main interpreter had the
opportunity to handle signals.

COMPUTE_EVAL_BREAKER() and SIGNAL_PENDING_SIGNALS() no longer set
eval_breaker to 1 if the current thread must not handle signals.

https://bugs.python.org/issue40010

@vstinner vstinner mentioned this pull request Mar 19, 2020
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@vstinner

vstinner commented Mar 19, 2020

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I merged PR #19066 which makes https://bugs.python.org/issue40010 worse for subinterpreters if I understand correctly. This PR should make subinterpreter as efficient as they were, or even more efficient, to handle signals.

@aeros aeros added the performance Performance or resource usage label Mar 19, 2020
@vstinner

vstinner commented Mar 19, 2020

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macOS failed

test.pythoninfo failed with:

ERROR: collect_pwd() failed
Traceback (most recent call last):
  File "/Users/runner/runners/2.165.2/work/cpython/cpython/Lib/test/pythoninfo.py", line 761, in collect_info
    collect_func(info_add)
  File "/Users/runner/runners/2.165.2/work/cpython/cpython/Lib/test/pythoninfo.py", line 336, in collect_pwd
    groups = os.getgrouplist(entry.pw_name, entry.pw_gid)
OSError: [Errno 0] Error

test_ttk_guionly failed on Ubuntu:

(...)
test_initialization_no_master (tkinter.test.test_ttk.test_extensions.LabeledScaleTest) ... ok
test_resize (tkinter.test.test_ttk.test_extensions.LabeledScaleTest) ... ok
test_variable_change (tkinter.test.test_ttk.test_extensions.LabeledScaleTest) ... Timeout (0:20:00)!
Thread 0x00007fa8861ec080 (most recent call first):
  File "/home/runner/work/cpython/cpython/Lib/tkinter/__init__.py", line 697 in wait_visibility
  File "/home/runner/work/cpython/cpython/Lib/tkinter/test/test_ttk/test_extensions.py", line 147 in test_variable_change
  File "/home/runner/work/cpython/cpython/Lib/unittest/case.py", line 616 in _callTestMethod
(...)

These two errors are unrelated to my PR.

@vstinner
bpo-40010: Optimize signal handling in multithreaded applications …
8f58946 
If a thread different than the main thread gets a signal, the
bytecode evaluation loop is no longer interrupted at each bytecode
instruction to check for pending signals which cannot be handled.
Only the main thread of the main interpreter can handle signals.

Previously, the bytecode evaluation loop was interrupted at each
instruction until the main thread handles signals.

Changes:

* COMPUTE_EVAL_BREAKER() and SIGNAL_PENDING_SIGNALS() no longer set
  eval_breaker to 1 if the current thread cannot handle signals.
* take_gil() now always recomputes eval_breaker.
@vstinner vstinner merged commit 5a3a71d into python:master Mar 19, 2020
@vstinner vstinner deleted the signal_pending_signals branch March 19, 2020 16:40
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