void key_fsgid_changed(struct task_struct *tsk)
{
	/* update the ownership of the thread keyring */
	BUG_ON(!tsk->cred);
	if (tsk->cred->thread_keyring) {
		down_write(&tsk->cred->thread_keyring->sem);
		tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
		up_write(&tsk->cred->thread_keyring->sem);
	}
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.