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Message-Id: <200708142023.23994.rjw@sisk.pl>
Date: Tue, 14 Aug 2007 20:23:23 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Pavel Machek <pavel@....cz>
Cc: Andres Salomon <dilinger@...ued.net>, akpm@...ux-foundation.org,
kernel list <linux-kernel@...r.kernel.org>
Subject: Re: + serial-turn-serial-console-suspend-a-boot-rather-than-compile-time-option.patch added to -mm tree
On Tuesday, 14 August 2007 12:39, Pavel Machek wrote:
> Hi!
>
> > Thanks, updated below!
> >
> >
> >
> > serial: turn serial console suspend a boot rather than compile time option
> >
> > From: Andres Salomon <dilinger@...ian.org>
> >
> > Currently, there's a CONFIG_DISABLE_CONSOLE_SUSPEND that allows one to stop
> > the serial console from being suspended when the rest of the machine goes
> > to sleep. This is incredibly useful for debugging power
> > management-related
>
> Actually, this should not be configurable. We should simply enable
> console during suspend for consoles that can handle this,
> automatically.... this patch does just that. I hope I separated it
> correctly.
>
> It may be that something else than netconsole is broken during
> suspend... but it should not be, we were running without suspending
> consoles for quite long; we can always fix it when we hit the bug.
>
> Signed-off-by: Pavel Machek <pavel@...e.cz>
>
Well, my box used to hang on suspend when the framebuffer console was enabled.
It doesn't do that any more, though, so it may be safe.
I think we can do this, but I expect some bug reports to show up as a result.
Greetings,
Rafael
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index 69233f6..7f7c2ce 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -115,6 +115,7 @@ static int init_netconsole(void)
> if (err)
> return err;
>
> + disable_console_on_suspend++;
> register_console(&netconsole);
> printk(KERN_INFO "netconsole: network logging started\n");
> return 0;
> @@ -123,6 +124,7 @@ static int init_netconsole(void)
> static void cleanup_netconsole(void)
> {
> unregister_console(&netconsole);
> + disable_console_on_suspend--;
> netpoll_cleanup(&np);
> }
>
> diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
> index 030a606..426c3d6 100644
> --- a/drivers/serial/serial_core.c
> +++ b/drivers/serial/serial_core.c
> @@ -1941,12 +1941,10 @@ int uart_suspend_port(struct uart_driver
>
> mutex_lock(&state->mutex);
>
> -#ifdef CONFIG_DISABLE_CONSOLE_SUSPEND
> if (uart_console(port)) {
> mutex_unlock(&state->mutex);
> return 0;
> }
> -#endif
>
> if (state->info && state->info->flags & UIF_INITIALIZED) {
> const struct uart_ops *ops = port->ops;
> @@ -1989,12 +1987,10 @@ int uart_resume_port(struct uart_driver
>
> mutex_lock(&state->mutex);
>
> -#ifdef CONFIG_DISABLE_CONSOLE_SUSPEND
> if (uart_console(port)) {
> mutex_unlock(&state->mutex);
> return 0;
> }
> -#endif
>
> uart_change_pm(state, 0);
>
> diff --git a/include/linux/console.h b/include/linux/console.h
> index 56a7bcd..2e2b9bc 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -121,14 +121,11 @@ extern void console_stop(struct console
> extern void console_start(struct console *);
> extern int is_console_locked(void);
>
> -#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
> +extern int disable_console_on_suspend;
> +
> /* Suspend and resume console messages over PM events */
> extern void suspend_console(void);
> extern void resume_console(void);
> -#else
> -static inline void suspend_console(void) {}
> -static inline void resume_console(void) {}
> -#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
>
> int mda_console_init(void);
> void prom_con_init(void);
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 412859f..a68e841 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -44,17 +44,6 @@ config PM_VERBOSE
> ---help---
> This option enables verbose messages from the Power Management code.
>
> -config DISABLE_CONSOLE_SUSPEND
> - bool "Keep console(s) enabled during suspend/resume (DANGEROUS)"
> - depends on PM_DEBUG && PM_SLEEP
> - default n
> - ---help---
> - This option turns off the console suspend mechanism that prevents
> - debug messages from reaching the console during the suspend/resume
> - operations. This may be helpful when debugging device drivers'
> - suspend/resume routines, but may itself lead to problems, for example
> - if netconsole is used.
> -
> config PM_TRACE
> bool "Suspend/resume event tracing"
> depends on PM_DEBUG && X86 && PM_SLEEP && EXPERIMENTAL
> diff --git a/kernel/printk.c b/kernel/printk.c
> index bd2cd06..5a2d6c0 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -751,7 +751,9 @@ int update_console_cmdline(char *name, i
> return -1;
> }
>
> -#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
> +
> +int disable_console_on_suspend;
> +
> /**
> * suspend_console - suspend the console subsystem
> *
> @@ -759,17 +761,22 @@ #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
> */
> void suspend_console(void)
> {
> - printk("Suspending console(s)\n");
> - acquire_console_sem();
> - console_suspended = 1;
> + if (disable_console_on_suspend) {
> + printk("Suspending console(s)\n");
> + acquire_console_sem();
> + console_suspended = 1;
> + }
> }
>
> void resume_console(void)
> {
> - console_suspended = 0;
> - release_console_sem();
> + if (console_suspended) {
> + BUG_ON(!disable_console_on_suspend);
> + console_suspended = 0;
> + release_console_sem();
> + }
> }
> -#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
> +
>
> /**
> * acquire_console_sem - lock the console system for exclusive use.
>
--
"Premature optimization is the root of all evil." - Donald Knuth
-
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