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@xxxxxxxxxx>

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@xxxxxxx>


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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