Hi Geert,
On 03/21/2014 09:23 AM, Geert Uytterhoeven wrote:
Hi Peter,
On Fri, Mar 21, 2014 at 2:06 PM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote:
@@ -2681,10 +2683,12 @@ int uart_remove_one_port(struct uart_driver *drv,
struct uart_port *uport)
}
/*
- * If the port is used as a console, unregister it
+ * If the port is used as a console, unregister it, and power it
down
*/
- if (uart_console(uport))
+ if (uart_console(uport)) {
unregister_console(uport->cons);
+ uart_change_pm(state, UART_PM_STATE_OFF);
Won't this power off the port while tty consoles may still be open?
I didn't see that actually happening.
Ok, but I still think this isn't right. See below.
I think the right thing here is to unregister_console then set uport->cons =
NULL
[uport->cons is properly reassigned when/if a port is re-added via
uart_add_one_port()).]
But indeed, for concistency/symmetry uport->state and uport->cons
should be resend, but that's something separate.
I don't see this as being a "looks good" problem; I see this as being
"what's the right way to teardown a uart device that's going away when
a tty console is running on it", and there are too many problems with
uart_remove_one_port() doing:
state->uart_port = NULL
to keep with that solution.
Then, uart_close() will power off the port when all ttys using the port have
been closed.
uart_close() won't get that far, so uart_change_pm() won't be called.
And this is the central problem: uart_close() must complete normally
if a tty console is still running on a device.
For example, if uart_shutdown() isn't getting called, then who's freeing
the ring buffer page?
See also https://lkml.org/lkml/2014/3/10/651, and my workaround for the
crash https://lkml.org/lkml/2014/3/17/231.
See my comments to the v2 patch there.
Regards,
Peter Hurley
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