Avoid TSan reported race in `run_udp_echo_server` #122187

colesbury · 2024-07-23T17:45:51Z

The test_asyncio.test_sock_lowlevel.py test uses a UDP echo server:

Lines 288 to 310 in a15fede

    
           def echo_datagrams(sock): 
        
               while True: 
        
                   data, addr = sock.recvfrom(4096) 
        
                   if data == b'STOP': 
        
                       sock.close() 
        
                       break 
        
                   else: 
        
                       sock.sendto(data, addr) 
        
           @contextlib.contextmanager 
        
           def run_udp_echo_server(*, host='127.0.0.1', port=0): 
        
               addr_info = socket.getaddrinfo(host, port, type=socket.SOCK_DGRAM) 
        
               family, type, proto, _, sockaddr = addr_info[0] 
        
               sock = socket.socket(family, type, proto) 
        
               sock.bind((host, port)) 
        
               thread = threading.Thread(target=lambda: echo_datagrams(sock)) 
        
               thread.start() 
        
               try: 
        
                   yield sock.getsockname() 
        
               finally: 
        
                   sock.sendto(b'STOP', sock.getsockname()) 
        
                   thread.join()

Thread sanitizer complains about the sock.sendto(b'STOP', sock.getsockname()) line in the main thread happening concurrently with the sock.close() in the echo_datagrams thread.

This seems a bit bogus to me: the sendto has to start before the close starts because it triggers the echo_datagrams shutdown, but it's easy enough to avoid the data race. I also think it's better in this case to do a small code change to the test, instead of adding or keeping a global suppression.

Linked PRs

The text was updated successfully, but these errors were encountered:

TSan doesn't fully recognize the synchronization via I/O, so ensure that socket name is retrieved earlier and use a different socket for sending the "STOP" message.

These tests fail when run under thread sanitizer due to the use of fork and threads..

TSan doesn't fully recognize the synchronization via I/O, so ensure that socket name is retrieved earlier and use a different socket for sending the "STOP" message.

…ythonGH-122189) TSan doesn't fully recognize the synchronization via I/O, so ensure that socket name is retrieved earlier and use a different socket for sending the "STOP" message. (cherry picked from commit 2f74b70) Co-authored-by: Sam Gross <colesbury@gmail.com>

…H-122189) (#122263) gh-122187: Avoid TSan reported race in `run_udp_echo_server` (GH-122189) TSan doesn't fully recognize the synchronization via I/O, so ensure that socket name is retrieved earlier and use a different socket for sending the "STOP" message. (cherry picked from commit 2f74b70) Co-authored-by: Sam Gross <colesbury@gmail.com>

colesbury added the topic-free-threading label Jul 23, 2024

bedevere-app bot mentioned this issue Jul 23, 2024

gh-122187: Avoid TSan reported race in run_udp_echo_server #122189

Merged

colesbury added a commit to colesbury/cpython that referenced this issue Jul 23, 2024

pythongh-122187: Skip tests that use threads after fork

f9cfafe

These tests fail when run under thread sanitizer due to the use of fork and threads..

bedevere-app bot mentioned this issue Jul 23, 2024

gh-117657: Skip tests that use threads after fork #122194

Merged

bedevere-app bot mentioned this issue Jul 25, 2024

[3.13] gh-122187: Avoid TSan reported race in run_udp_echo_server (GH-122189) #122263

Merged

kumaraditya303 closed this as completed Jul 25, 2024

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Avoid TSan reported race in `run_udp_echo_server` #122187

Avoid TSan reported race in `run_udp_echo_server` #122187

colesbury commented Jul 23, 2024 •

edited by bedevere-app bot

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Avoid TSan reported race in run_udp_echo_server #122187

Avoid TSan reported race in run_udp_echo_server #122187

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colesbury commented Jul 23, 2024 • edited by bedevere-app bot Loading

Linked PRs

Avoid TSan reported race in `run_udp_echo_server` #122187

Avoid TSan reported race in `run_udp_echo_server` #122187

colesbury commented Jul 23, 2024 •

edited by bedevere-app bot

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