Haren Myneni <ha...@linux.ibm.com> writes:
> Process close windows after its requests are completed. In multi-thread
> applications, child can open a window but release FD will not be called
> upon its exit. Parent thread will be closing it later upon its exit.
What if the parent exits first?
> The parent can also send NX requests with this window and NX can
> generate page faults. After kernel handles the page fault, send
> signal to process by using PID if CSB address is invalid. Parent
> thread will not receive signal since its PID is different from the one
> saved in vas_window. So use tgid in case if the task for the pid saved
> in window is not running and send signal to its parent.
>
> To prevent reusing the pid until the window closed, take reference to
> pid and task mm.
That text is all very dense. Can you please flesh it out and reword it
to clearly spell out what's going on in much more detail.
> diff --git a/arch/powerpc/platforms/powernv/vas-window.c
> b/arch/powerpc/platforms/powernv/vas-window.c
> index a45d81d..7587258 100644
> --- a/arch/powerpc/platforms/powernv/vas-window.c
> +++ b/arch/powerpc/platforms/powernv/vas-window.c
> @@ -1266,8 +1300,17 @@ int vas_win_close(struct vas_window *window)
> poll_window_castout(window);
>
> /* if send window, drop reference to matching receive window */
> - if (window->tx_win)
> + if (window->tx_win) {
> + if (window->user_win) {
> + /* Drop references to pid and mm */
> + put_pid(window->pid);
> + if (window->mm) {
> + mmdrop(window->mm);
> + mm_context_remove_copro(window->mm);
That seems backward. Once you drop the reference the mm can be freed
can't it?
> + }
> + }
> put_rx_win(window->rxwin);
> + }
>
> vas_window_free(window);
cheers
