gh-127081: add critical sections to dbm objects

[duaneg]

The dbm_* functions are not thread-safe, naturally. Add critical sections to protect their use.

• Issue: Thread-unsafe libc functions #127081

[ZeroIntensity]

In general, it's easier to add lock_held variations of functions instead of adding inline critical sections with goto. For example:

static int
dbm_something_lock_held(PyObject *self)
{
    /* ... */
}

static int
dbm_something(PyObject *self)
{
    int result;
    Py_BEGIN_CRITICAL_SECTION(self);
    result = dbm_something_lock_held(self);
    Py_END_CRITICAL_SECTION();
    return result;
}

Would you mind switching over to that pattern here?

[duaneg]

In general, it's easier to add lock_held variations of functions instead of adding inline critical sections with goto.... Would you mind switching over to that pattern here?

For sure, that would be much more robust, thanks!

[corona10]

Sorry for the delay, I will review during the PyCon sprint.

[ZeroIntensity]

LGTM as well

[corona10]

Would you like to update clinic again?

[corona10]

Oh it's not relatede to dbms.

[miss-islington-app]

Thanks @duaneg for the PR, and @corona10 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-app]

GH-139996 is a backport of this pull request to the 3.14 branch.