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    Subject[PATCH 2/3] PM: Make it possible to disable console suspending
    Date
    Change suspend_console() so that it waits for all consoles to flush the
    remaining messages and make it possible to switch the console suspending
    off with the help of a Kconfig option.

    Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
    Acked-by: Pavel Machek <pavel@ucw.cz>
    ---
    include/linux/console.h | 5 +++++
    kernel/power/Kconfig | 11 +++++++++++
    kernel/printk.c | 8 ++++++++
    3 files changed, 24 insertions(+)

    Index: linux-2.6.18-rc4-mm1/include/linux/console.h
    ===================================================================
    --- linux-2.6.18-rc4-mm1.orig/include/linux/console.h 2006-08-16 11:59:56.000000000 +0200
    +++ linux-2.6.18-rc4-mm1/include/linux/console.h 2006-08-16 12:00:01.000000000 +0200
    @@ -120,9 +120,14 @@ extern void console_stop(struct console
    extern void console_start(struct console *);
    extern int is_console_locked(void);

    +#ifndef CONFIG_DISABLE_CONSOLE_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 */

    /* Some debug stub to catch some of the obvious races in the VT code */
    #if 1
    Index: linux-2.6.18-rc4-mm1/kernel/power/Kconfig
    ===================================================================
    --- linux-2.6.18-rc4-mm1.orig/kernel/power/Kconfig 2006-08-16 11:59:56.000000000 +0200
    +++ linux-2.6.18-rc4-mm1/kernel/power/Kconfig 2006-08-16 12:01:26.000000000 +0200
    @@ -36,6 +36,17 @@ config PM_DEBUG
    code. This is helpful when debugging and reporting various PM bugs,
    like suspend support.

    +config PM_DISABLE_CONSOLE_SUSPEND
    + bool "Keep console(s) enabled during suspend/resume (DANGEROUS)"
    + depends on PM && PM_DEBUG
    + 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 && PM_DEBUG && X86_32 && EXPERIMENTAL
    Index: linux-2.6.18-rc4-mm1/kernel/printk.c
    ===================================================================
    --- linux-2.6.18-rc4-mm1.orig/kernel/printk.c 2006-08-16 11:59:56.000000000 +0200
    +++ linux-2.6.18-rc4-mm1/kernel/printk.c 2006-08-16 12:08:59.000000000 +0200
    @@ -702,6 +702,7 @@ int __init add_preferred_console(char *n
    return 0;
    }

    +#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
    /**
    * suspend_console - suspend the console subsystem
    *
    @@ -709,8 +710,14 @@ int __init add_preferred_console(char *n
    */
    void suspend_console(void)
    {
    + printk("Suspending console(s)\n");
    acquire_console_sem();
    console_suspended = 1;
    + /* This is needed so that all of the messages that have already been
    + * written to all consoles can be actually transmitted (eg. over a
    + * network) before we try to suspend the consoles' devices.
    + */
    + ssleep(2);
    }

    void resume_console(void)
    @@ -718,6 +725,7 @@ void resume_console(void)
    console_suspended = 0;
    release_console_sem();
    }
    +#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */

    /**
    * acquire_console_sem - lock the console system for exclusive use.
    -
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