8000 gh-116522: Stop the world before fork() and during shutdown by colesbury · Pull Request #116607 · python/cpython · GitHub
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gh-116522: Stop the world before fork() and during shutdown #116607

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Merged
merged 3 commits into from
Mar 21, 2024
Merged

gh-116522: Stop the world before fork() and during shutdown #116607

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c2ebedb
gh-116522: Stop the world before fork() and during shutdown
colesbury Mar 8, 2024
b13d1e5
Move stop-the-world call before setting finalized
colesbury Mar 12, 2024
4772a69
Add comment and assertion to warn_about_fork_with_threads
colesbury Mar 20, 2024
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Add comment and assertion to warn_about_fork_with_threads
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@colesbury
colesbury committed Mar 20, 2024
commit 4772a69439a484bb1c6c2f3a485c57427839aeb1
16 changes: 12 additions & 4 deletions Modules/posixmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7737,10 +7737,15 @@ os_register_at_fork_impl(PyObject *module, PyObject *before,
// running in the process. Best effort, silent if unable to count threads.
// Constraint: Quick. Never overcounts. Never leaves an error set.
//
// This code might do an import, thus acquiring the import lock, which
// PyOS_BeforeFork() also does. As this should only be called from
// the parent process, it is in the same thread so that works.
static void warn_about_fork_with_threads(const char* name) {
// This should only be called from the parent process after
// PyOS_AfterFork_Parent().
static void
warn_about_fork_with_threads(const char* name)
{
// It's not safe to issue the warning while the world is stopped, because
// other threads might be holding locks that we need, which would deadlock.
assert(!_PyRuntime.stoptheworld.world_stopped);

// TODO: Consider making an `os` module API to return the current number
// of threads in the process. That'd presumably use this platform code but
// raise an error rather than using the inaccurate fallback.
Expand Down Expand Up @@ -7866,6 +7871,7 @@ os_fork1_impl(PyObject *module)
} else {
/* parent: release the import lock. */
PyOS_AfterFork_Parent();
// After PyOS_AfterFork_Parent() starts the world to avoid deadlock.
warn_about_fork_with_threads("fork1");
}
if (pid == -1) {
Expand Down Expand Up @@ -7914,6 +7920,7 @@ os_fork_impl(PyObject *module)
} else {
/* parent: release the import lock. */
PyOS_AfterFork_Parent();
// After PyOS_AfterFork_Parent() starts the world to avoid deadlock.
warn_about_fork_with_threads("fork");
}
if (pid == -1) {
Expand Down Expand Up @@ -8745,6 +8752,7 @@ os_forkpty_impl(PyObject *module)
} else {
/* parent: release the import lock. */
PyOS_AfterFork_Parent();
// After PyOS_AfterFork_Parent() starts the world to avoid deadlock.
warn_about_fork_with_threads("forkpty");
}
if (pid == -1) {
Expand Down
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