On Tue, 3 Dec 2019 12:09:43 +0530 Amol Grover <frextrite@xxxxxxxxx> wrote: > - Add more information about listRCU patterns taking examples > from audit subsystem in the linux kernel. > > - The initially written audit examples are kept, even though they are > slightly different in the kernel. > > - Modify inline text for better passage quality. > > - Fix typo in code-blocks and improve code comments. > > - Add text formatting (italics, bold and code) for better emphasis. Thanks for improving the documentation! I'll leave the RCU stuff to the experts, but I do have one request... [...] > +When a process exits, ``release_task()`` calls ``list_del_rcu(&p->tasks)`` under > +``tasklist_lock`` writer lock protection, to remove the task from the list of > +all tasks. The ``tasklist_lock`` prevents concurrent list additions/removals > +from corrupting the list. Readers using ``for_each_process()`` are not protected > +with the ``tasklist_lock``. To prevent readers from noticing changes in the list > +pointers, the ``task_struct`` object is freed only after one or more grace > +periods elapse (with the help of ``call_rcu()``). This deferring of destruction > +ensures that any readers traversing the list will see valid ``p->tasks.next`` > +pointers and deletion/freeing can happen in parallel with traversal of the list. > +This pattern is also called an **existence lock**, since RCU pins the object in > +memory until all existing readers finish. Please don't put function names as literal text. If you just say call_rcu(), it will be formatted correctly and cross-linked to the appropriate kerneldoc entry. Saying ``call_rcu()`` defeats that and clutters the plain-text reading experience. Thanks, jon
