python / python/cpython

Does CPython >= 3.10, <=3.12 support a thread-safe increment?

未關閉
#134,212 10 則留言 0 個 reaction 已指派 0 人 在 GitHub 檢視

還沒有人認領這個 Issue。

docs
主要語言
Python
星號
77.2k
分支
36k
PR 指標待擷取

描述

Documentation

There is no information about it in docs. But the code demonstrates that increment works correctly in multithreading context.

import concurrent.futures


def inc():
    global count
    for _ in range(1000):
        count += 1

for threads_count in range(1, 101):
    for _ in range(3):
        count = 0
        with concurrent.futures.ThreadPoolExecutor(max_workers=threads_count) as exe:
            for _ in range(10000):
                exe.submit(inc)

        print(f"{threads_count=}, {count=}")


import dis
dis.dis(inc)
output

threads=1, count=10000000
threads=1, count=10000000
threads=1, count=10000000
threads=2, count=10000000
threads=2, count=10000000
threads=2, count=10000000
threads=3, count=10000000
threads=3, count=10000000
threads=3, count=10000000
threads=4, count=10000000
threads=4, count=10000000
threads=4, count=10000000
threads=5, count=10000000
threads=5, count=10000000
threads=5, count=10000000
threads=6, count=10000000
threads=6, count=10000000
threads=6, count=10000000
threads=7, count=10000000
threads=7, count=10000000
threads=7, count=10000000
threads=8, count=10000000
threads=8, count=10000000
threads=8, count=10000000
threads=9, count=10000000
threads=9, count=10000000
threads=9, count=10000000
threads=10, count=10000000
threads=10, count=10000000
threads=10, count=10000000
threads=11, count=10000000
threads=11, count=10000000
threads=11, count=10000000
threads=12, count=10000000
threads=12, count=10000000
threads=12, count=10000000
threads=13, count=10000000
threads=13, count=10000000
threads=13, count=10000000
threads=14, count=10000000
threads=14, count=10000000
threads=14, count=10000000
threads=15, count=10000000
threads=15, count=10000000
threads=15, count=10000000
threads=16, count=10000000
threads=16, count=10000000
threads=16, count=10000000
threads=17, count=10000000
threads=17, count=10000000
threads=17, count=10000000
threads=18, count=10000000
threads=18, count=10000000
threads=18, count=10000000
threads=19, count=10000000
threads=19, count=10000000
threads=19, count=10000000
threads=20, count=10000000
threads=20, count=10000000
threads=20, count=10000000
threads=21, count=10000000
threads=21, count=10000000
threads=21, count=10000000
threads=22, count=10000000
threads=22, count=10000000
threads=22, count=10000000
threads=23, count=10000000
threads=23, count=10000000
threads=23, count=10000000
threads=24, count=10000000
threads=24, count=10000000
threads=24, count=10000000
threads=25, count=10000000
threads=25, count=10000000
threads=25, count=10000000
threads=26, count=10000000
threads=26, count=10000000
threads=26, count=10000000
threads=27, count=10000000
threads=27, count=10000000
threads=27, count=10000000
threads=28, count=10000000
threads=28, count=10000000
threads=28, count=10000000
threads=29, count=10000000
threads=29, count=10000000
threads=29, count=10000000
threads=30, count=10000000
threads=30, count=10000000
threads=30, count=10000000
threads=31, count=10000000
threads=31, count=10000000
threads=31, count=10000000
threads=32, count=10000000
threads=32, count=10000000
threads=32, count=10000000
threads=33, count=10000000
threads=33, count=10000000
threads=33, count=10000000
threads=34, count=10000000
threads=34, count=10000000
threads=34, count=10000000
threads=35, count=10000000
threads=35, count=10000000
threads=35, count=10000000
threads=36, count=10000000
threads=36, count=10000000
threads=36, count=10000000
threads=37, count=10000000
threads=37, count=10000000
threads=37, count=10000000
threads=38, count=10000000
threads=38, count=10000000
threads=38, count=10000000
threads=39, count=10000000
threads=39, count=10000000
threads=39, count=10000000
threads=40, count=10000000
threads=40, count=10000000
threads=40, count=10000000
threads=41, count=10000000
threads=41, count=10000000
threads=41, count=10000000
threads=42, count=10000000
threads=42, count=10000000
threads=42, count=10000000
threads=43, count=10000000
threads=43, count=10000000
threads=43, count=10000000
threads=44, count=10000000
threads=44, count=10000000
threads=44, count=10000000
threads=45, count=10000000
threads=45, count=10000000
threads=45, count=10000000
threads=46, count=10000000
threads=46, count=10000000
threads=46, count=10000000
threads=47, count=10000000
threads=47, count=10000000
threads=47, count=10000000
threads=48, count=10000000
threads=48, count=10000000
threads=48, count=10000000
threads=49, count=10000000
threads=49, count=10000000
threads=49, count=10000000
threads=50, count=10000000
threads=50, count=10000000
threads=50, count=10000000
threads=51, count=10000000
threads=51, count=10000000
threads=51, count=10000000
threads=52, count=10000000
threads=52, count=10000000
threads=52, count=10000000
threads=53, count=10000000
threads=53, count=10000000
threads=53, count=10000000
threads=54, count=10000000
threads=54, count=10000000
threads=54, count=10000000
threads=55, count=10000000
threads=55, count=10000000
threads=55, count=10000000
threads=56, count=10000000
threads=56, count=10000000
threads=56, count=10000000
threads=57, count=10000000
threads=57, count=10000000
threads=57, count=10000000
threads=58, count=10000000
threads=58, count=10000000
threads=58, count=10000000
threads=59, count=10000000
threads=59, count=10000000
threads=59, count=10000000
threads=60, count=10000000
threads=60, count=10000000
threads=60, count=10000000
threads=61, count=10000000
threads=61, count=10000000
threads=61, count=10000000
threads=62, count=10000000
threads=62, count=10000000
threads=62, count=10000000
threads=63, count=10000000
threads=63, count=10000000
threads=63, count=10000000
threads=64, count=10000000
threads=64, count=10000000
threads=64, count=10000000
threads=65, count=10000000
threads=65, count=10000000
threads=65, count=10000000
threads=66, count=10000000
threads=66, count=10000000
threads=66, count=10000000
threads=67, count=10000000
threads=67, count=10000000
threads=67, count=10000000
threads=68, count=10000000
threads=68, count=10000000
threads=68, count=10000000
threads=69, count=10000000
threads=69, count=10000000
threads=69, count=10000000
threads=70, count=10000000
threads=70, count=10000000
threads=70, count=10000000
threads=71, count=10000000
threads=71, count=10000000
threads=71, count=10000000
threads=72, count=10000000
threads=72, count=10000000
threads=72, count=10000000
threads=73, count=10000000
threads=73, count=10000000
threads=73, count=10000000
threads=74, count=10000000
threads=74, count=10000000
threads=74, count=10000000
threads=75, count=10000000
threads=75, count=10000000
threads=75, count=10000000
threads=76, count=10000000
threads=76, count=10000000
threads=76, count=10000000
threads=77, count=10000000
threads=77, count=10000000
threads=77, count=10000000
threads=78, count=10000000
threads=78, count=10000000
threads=78, count=10000000
threads=79, count=10000000
threads=79, count=10000000
threads=79, count=10000000
threads=80, count=10000000
threads=80, count=10000000
threads=80, count=10000000
threads=81, count=10000000
threads=81, count=10000000
threads=81, count=10000000
threads=82, count=10000000
threads=82, count=10000000
threads=82, count=10000000
threads=83, count=10000000
threads=83, count=10000000
threads=83, count=10000000
threads=84, count=10000000
threads=84, count=10000000
threads=84, count=10000000
threads=85, count=10000000
threads=85, count=10000000
threads=85, count=10000000
threads=86, count=10000000
threads=86, count=10000000
threads=86, count=10000000
threads=87, count=10000000
threads=87, count=10000000
threads=87, count=10000000
threads=88, count=10000000
threads=88, count=10000000
threads=88, count=10000000
threads=89, count=10000000
threads=89, count=10000000
threads=89, count=10000000
threads=90, count=10000000
threads=90, count=10000000
threads=90, count=10000000
threads=91, count=10000000
threads=91, count=10000000
threads=91, count=10000000
threads=92, count=10000000
threads=92, count=10000000
threads=92, count=10000000
threads=93, count=10000000
threads=93, count=10000000
threads=93, count=10000000
threads=94, count=10000000
threads=94, count=10000000
threads=94, count=10000000
threads=95, count=10000000
threads=95, count=10000000
threads=95, count=10000000
threads=96, count=10000000
threads=96, count=10000000
threads=96, count=10000000
threads=97, count=10000000
threads=97, count=10000000
threads=97, count=10000000
threads=98, count=10000000
threads=98, count=10000000
threads=98, count=10000000
threads=99, count=10000000
threads=99, count=10000000
threads=99, count=10000000
threads=100, count=10000000
threads=100, count=10000000
threads=100, count=10000000
11 0 LOAD_GLOBAL 0 (range)
2 LOAD_CONST 1 (1000)
4 CALL_FUNCTION 1
6 GET_ITER
>> 8 FOR_ITER 6 (to 22)
10 STORE_FAST 0 (_)

12 12 LOAD_GLOBAL 1 (count)
14 LOAD_CONST 2 (1)
16 INPLACE_ADD
18 STORE_GLOBAL 1 (count)
20 JUMP_ABSOLUTE 4 (to 8)

11 >> 22 LOAD_CONST 0 (None)
24 RETURN_VALUE

Looks like '+=' isn't an atomic op. But stiil I have a correct result.

Can we just use it as a guarantee or it is just an accent coincidence?

貢獻指南

開啟貢獻指南

從這裡開始

  1. 先讀完整個 Issue，再讀專案的貢獻指南。
  2. 在 Issue 下留言說明你要接手 —— 這能避免兩個人做同樣的事。
  3. Fork 儲存庫，在一個分支上完成修改。
  4. 送出 Pull Request，並在描述裡引用這個 Issue 編號。

研究方向

從已回報的 ThreadPoolExecutor 範例、inc 函式及其反組譯開始。檢視現有的 Python threading 與語言參考文件，以確定在 CPython 3.10–3.12 中適用何種保證（如果存在）。當特定版本的行為以及是否可以依賴 += 都獲得清楚記錄時，即視為完成。

由索引模型根據 Issue 內容生成。

評估

技術堆疊
python
領域
documentation
Issue 類型
文件
難度
5/5
預估耗時
一週以上
活躍度
停滯
描述清晰度
需要釐清
新手友好度
25/100

把新 issue 寄到你的電子郵件信箱

精選適合新手參與的 GitHub issue 摘要。