8000 gh-118138: Adds test for multithreaded writes to files. by elistevens · Pull Request #119107 · python/cpython · GitHub
[go: up one dir, main page]
Skip to content

gh-118138: Adds test for multithreaded writes to files. #119107

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 4 commits into from
Closed

gh-118138: Adds test for multithreaded writes to files. #119107

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
dca6eb6
Adds test for multithreaded writes to files.
elistevens May 17, 2024
997dbc2
Calls executor.shutdown before closing file.
elistevens May 17, 2024
3f05fd9
Fixes race conditions from multithreaded writes.
elistevens May 17, 2024
d156d3c
Update test_io_threading.py to not suffer from interleaved prints
elistevens May 30, 2024
File filter

Filter by extension

Filter by extension
8000
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Next Next commit
Adds test for multithreaded writes to files. 
Multithreaded writes to files (including standard calls to print() from
threads) can result in assertion failures and potentially missed output due to
race conditions in _io_TextIOWrapper_write_impl and _textiowrapper_writeflush.

See: #118138
  • Loading branch information
@elistevens
elistevens committed May 17, 2024
commit dca6eb690f19ce49af1d570623ae26f402d7d285
36 changes: 36 additions & 0 deletions Lib/test/test_io_threading.py
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
import unittest
from concurrent.futures import ThreadPoolExecutor


NUM_THREADS = 100
NUM_LOOPS = 10

def looping_print_to_file(f, i):
for j in range(NUM_LOOPS):
# p = 'x' * 90 + '123456789'
p = f"{i:2}i,{j}j\n" + '0123456789' * 10
print(p, file=f)

class IoThreadingTestCase(unittest.TestCase):
def test_io_threading(self):
with ThreadPoolExecutor(max_workers=NUM_THREADS) as executor:
with open('test_io_threading.out', 'w') as f:
for i in range(NUM_THREADS):
executor.submit(looping_print_to_file, f, i)

executor.shutdown(wait=True)

with open('test_io_threading.out', 'r') as f:
lines = set(x.rstrip() for x in f.readlines() if ',' in x)

assert len(lines) == NUM_THREADS * NUM_LOOPS, repr(len(lines))

for i in range(NUM_THREADS):
for j in range(NUM_LOOPS):
p = f"{i:2}i,{j}j"

assert p in lines, repr(p)


if __name__ == "__main__":
unittest.main()
4 changes: 4 additions & 0 deletions Modules/_io/textio.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1729,6 +1729,10 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)
Py_DECREF(b);
return NULL;
}
// The assumption that self won't have been modified from another
// thread between the flush above and the assignment below is
// incorrect.
assert(self->pending_bytes == NULL);
self->pending_bytes = b;
}
else if (!PyList_CheckExact(self->pending_bytes)) {
Expand Down
0