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    Subject[patch] Fixes and cleanups for earlyprintk aka boot console.
      Hi,

    The console subsystem already has an idea of a boot console, using the
    CON_BOOT flag. The implementation has some flaws though. The major
    problem is that presence of a boot console makes register_console()
    ignore any other console devices (unless explicitly specified on the
    kernel command line).

    This patch fixes the console selection code to *not* consider a boot
    console a full-featured one, so the first non-boot console registering
    will become the default console instead. This way the unregister call
    for the boot console in the register_console() function actually
    triggers and the handover from the boot console to the real console
    device works smoothly. Added a printk for the handover, so you know
    which console device the output goes to when the boot console stops
    printing messages.

    The disable_early_printk() call is obsolete with that patch, explicitly
    disabling the early console isn't needed any more as it works
    automagically with that patch.

    I've walked through the tree, dropped all disable_early_printk()
    instances found below arch/ and tagged the consoles with CON_BOOT if
    needed.

    The code is tested on x86 only so far. It is probably a good idea to
    run it in -mm for a while to shake out any architecture issues which
    might show up. Comments?

    cheers,

    Gerd

    --
    Gerd Hoffmann <kraxel@suse.de>
    Fixes and cleanups for earlyprintk aka boot console.

    The console subsystem already has an idea of a boot console, using the
    CON_BOOT flag. The implementation has some flaws though. The major
    problem is that presence of a boot console makes register_console()
    ignore any other console devices (unless explicitly specified on the
    kernel command line).

    This patch fixes the console selection code to *not* consider a boot
    console a full-featured one, so the first non-boot console registering
    will become the default console instead. This way the unregister call
    for the boot console in the register_console() function actually
    triggers and the handover from the boot console to the real console
    device works smoothly. Added a printk for the handover, so you know
    which console device the output goes to when the boot console stops
    printing messages.

    The disable_early_printk() call is obsolete with that patch, explicitly
    disabling the early console isn't needed any more as it works
    automagically with that patch.

    I've walked through the tree, dropped all disable_early_printk()
    instances found below arch/ and tagged the consoles with CON_BOOT if
    needed. The code is tested on x86 only so far.

    Signed-off-by: Gerd Hoffmann <kraxel@suse.de>
    Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    ---
    arch/alpha/kernel/setup.c | 9 ---------
    arch/alpha/kernel/srmcons.c | 2 +-
    arch/mips/cobalt/console.c | 5 -----
    arch/mips/dec/prom/console.c | 5 +----
    arch/mips/sgi-ip27/ip27-console.c | 5 -----
    arch/powerpc/kernel/udbg.c | 14 +-------------
    arch/sh/kernel/early_printk.c | 18 ++++++------------
    arch/sh64/kernel/early_printk.c | 8 +-------
    arch/x86_64/kernel/early_printk.c | 20 +++++---------------
    drivers/char/tty_io.c | 5 -----
    kernel/printk.c | 26 ++++++++++++++++----------
    11 files changed, 31 insertions(+), 86 deletions(-)

    ===================================================================
    Index: paravirt-2.6.20-git14-hg791/arch/x86_64/kernel/early_printk.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/x86_64/kernel/early_printk.c
    +++ paravirt-2.6.20-git14-hg791/arch/x86_64/kernel/early_printk.c
    @@ -244,22 +244,12 @@ static int __init setup_early_printk(cha
    early_console = &simnow_console;
    keep_early = 1;
    }
    +
    + if (keep_early)
    + early_console->flags &= ~CON_BOOT;
    + else
    + early_console->flags |= CON_BOOT;
    register_console(early_console);
    return 0;
    }
    -
    early_param("earlyprintk", setup_early_printk);
    -
    -void __init disable_early_printk(void)
    -{
    - if (!early_console_initialized || !early_console)
    - return;
    - if (!keep_early) {
    - printk("disabling early console\n");
    - unregister_console(early_console);
    - early_console_initialized = 0;
    - } else {
    - printk("keeping early console\n");
    - }
    -}
    -
    Index: paravirt-2.6.20-git14-hg791/kernel/printk.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/kernel/printk.c
    +++ paravirt-2.6.20-git14-hg791/kernel/printk.c
    @@ -931,8 +931,16 @@ void register_console(struct console *co
    {
    int i;
    unsigned long flags;
    + struct console *bootconsole = NULL;

    - if (preferred_console < 0)
    + if (console_drivers) {
    + if (console->flags & CON_BOOT)
    + return;
    + if (console_drivers->flags & CON_BOOT)
    + bootconsole = console_drivers;
    + }
    +
    + if (preferred_console < 0 || bootconsole || !console_drivers)
    preferred_console = selected_console;

    /*
    @@ -978,8 +986,11 @@ void register_console(struct console *co
    if (!(console->flags & CON_ENABLED))
    return;

    - if (console_drivers && (console_drivers->flags & CON_BOOT)) {
    - unregister_console(console_drivers);
    + if (bootconsole) {
    + printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
    + bootconsole->name, bootconsole->index,
    + console->name, console->index);
    + unregister_console(bootconsole);
    console->flags &= ~CON_PRINTBUFFER;
    }

    @@ -1030,16 +1041,11 @@ int unregister_console(struct console *c
    }
    }

    - /* If last console is removed, we re-enable picking the first
    - * one that gets registered. Without that, pmac early boot console
    - * would prevent fbcon from taking over.
    - *
    + /*
    * If this isn't the last console and it has CON_CONSDEV set, we
    * need to set it on the next preferred console.
    */
    - if (console_drivers == NULL)
    - preferred_console = selected_console;
    - else if (console->flags & CON_CONSDEV)
    + if (console_drivers != NULL && console->flags & CON_CONSDEV)
    console_drivers->flags |= CON_CONSDEV;

    release_console_sem();
    Index: paravirt-2.6.20-git14-hg791/drivers/char/tty_io.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/drivers/char/tty_io.c
    +++ paravirt-2.6.20-git14-hg791/drivers/char/tty_io.c
    @@ -141,8 +141,6 @@ static DECLARE_MUTEX(allocated_ptys_lock
    static int ptmx_open(struct inode *, struct file *);
    #endif

    -extern void disable_early_printk(void);
    -
    static void initialize_tty_struct(struct tty_struct *tty);

    static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
    @@ -3880,9 +3878,6 @@ void __init console_init(void)
    * set up the console device so that later boot sequences can
    * inform about problems etc..
    */
    -#ifdef CONFIG_EARLY_PRINTK
    - disable_early_printk();
    -#endif
    call = __con_initcall_start;
    while (call < __con_initcall_end) {
    (*call)();
    Index: paravirt-2.6.20-git14-hg791/arch/alpha/kernel/setup.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/alpha/kernel/setup.c
    +++ paravirt-2.6.20-git14-hg791/arch/alpha/kernel/setup.c
    @@ -744,15 +744,6 @@ setup_arch(char **cmdline_p)
    paging_init();
    }

    -void __init
    -disable_early_printk(void)
    -{
    - if (alpha_using_srm && srmcons_output) {
    - unregister_srm_console();
    - srmcons_output = 0;
    - }
    -}
    -
    static char sys_unknown[] = "Unknown";
    static char systype_names[][16] = {
    "0",
    Index: paravirt-2.6.20-git14-hg791/arch/alpha/kernel/srmcons.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/alpha/kernel/srmcons.c
    +++ paravirt-2.6.20-git14-hg791/arch/alpha/kernel/srmcons.c
    @@ -300,7 +300,7 @@ static struct console srmcons = {
    .write = srm_console_write,
    .device = srm_console_device,
    .setup = srm_console_setup,
    - .flags = CON_PRINTBUFFER,
    + .flags = CON_PRINTBUFFER | CON_BOOT,
    .index = -1,
    };

    Index: paravirt-2.6.20-git14-hg791/arch/mips/cobalt/console.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/mips/cobalt/console.c
    +++ paravirt-2.6.20-git14-hg791/arch/mips/cobalt/console.c
    @@ -40,8 +40,3 @@ void __init cobalt_early_console(void)

    printk("Cobalt: early console registered\n");
    }
    -
    -void __init disable_early_printk(void)
    -{
    - unregister_console(&cons_info);
    -}
    Index: paravirt-2.6.20-git14-hg791/arch/mips/dec/prom/console.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/mips/dec/prom/console.c
    +++ paravirt-2.6.20-git14-hg791/arch/mips/dec/prom/console.c
    @@ -29,7 +29,7 @@ static void __init prom_console_write(st
    static struct console promcons __initdata = {
    .name = "prom",
    .write = prom_console_write,
    - .flags = CON_PRINTBUFFER,
    + .flags = CON_PRINTBUFFER | CON_BOOT,
    .index = -1,
    };

    @@ -50,6 +50,3 @@ void __init unregister_prom_console(void
    promcons_output = 0;
    }
    }
    -
    -void disable_early_printk(void)
    - __attribute__((alias("unregister_prom_console")));
    Index: paravirt-2.6.20-git14-hg791/arch/mips/sgi-ip27/ip27-console.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/mips/sgi-ip27/ip27-console.c
    +++ paravirt-2.6.20-git14-hg791/arch/mips/sgi-ip27/ip27-console.c
    @@ -67,8 +67,3 @@ __init void ip27_setup_console(void)
    {
    register_console(&ioc3_console);
    }
    -
    -void __init disable_early_printk(void)
    -{
    - unregister_console(&ioc3_console);
    -}
    Index: paravirt-2.6.20-git14-hg791/arch/powerpc/kernel/udbg.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/powerpc/kernel/udbg.c
    +++ paravirt-2.6.20-git14-hg791/arch/powerpc/kernel/udbg.c
    @@ -142,24 +142,12 @@ static void udbg_console_write(struct co
    static struct console udbg_console = {
    .name = "udbg",
    .write = udbg_console_write,
    - .flags = CON_PRINTBUFFER | CON_ENABLED,
    + .flags = CON_PRINTBUFFER | CON_ENABLED | CON_BOOT,
    .index = -1,
    };

    static int early_console_initialized;

    -void __init disable_early_printk(void)
    -{
    - if (!early_console_initialized)
    - return;
    - if (strstr(boot_command_line, "udbg-immortal")) {
    - printk(KERN_INFO "early console immortal !\n");
    - return;
    - }
    - unregister_console(&udbg_console);
    - early_console_initialized = 0;
    -}
    -
    /* called by setup_system */
    void register_early_udbg_console(void)
    {
    Index: paravirt-2.6.20-git14-hg791/arch/sh/kernel/early_printk.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/sh/kernel/early_printk.c
    +++ paravirt-2.6.20-git14-hg791/arch/sh/kernel/early_printk.c
    @@ -192,20 +192,14 @@ int __init setup_early_printk(char *buf)
    }
    #endif

    - if (likely(early_console))
    + if (likely(early_console)) {
    + if (keep_early)
    + early_console->flags &= ~CON_BOOT;
    + else
    + early_console->flags |= CON_BOOT;
    register_console(early_console);
    + }

    return 0;
    }
    early_param("earlyprintk", setup_early_printk);
    -
    -void __init disable_early_printk(void)
    -{
    - if (!early_console_initialized || !early_console)
    - return;
    - if (!keep_early) {
    - printk("disabling early console\n");
    - unregister_console(early_console);
    - } else
    - printk("keeping early console\n");
    -}
    Index: paravirt-2.6.20-git14-hg791/arch/sh64/kernel/early_printk.c
    ===================================================================
    --- paravirt-2.6.20-git14-hg791.orig/arch/sh64/kernel/early_printk.c
    +++ paravirt-2.6.20-git14-hg791/arch/sh64/kernel/early_printk.c
    @@ -79,7 +79,7 @@ static struct console sh_console = {
    .name = "scifcon",
    .write = sh_console_write,
    .setup = sh_console_setup,
    - .flags = CON_PRINTBUFFER,
    + .flags = CON_PRINTBUFFER | CON_BOOT,
    .index = -1,
    };

    @@ -97,9 +97,3 @@ void __init enable_early_printk(void)

    register_console(&sh_console);
    }
    -
    -void disable_early_printk(void)
    -{
    - unregister_console(&sh_console);
    -}
    -
    \
     
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      Last update: 2007-02-20 12:39    [W:0.061 / U:31.596 seconds]
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