lkml.org 
[lkml]   [2007]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
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The disable_early_printk() call is obsolete with that patch, explicitly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The disable_early_printk() call is obsolete with that patch, explicitly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);
-}
-
\
 
 \ /
  Last update: 2007-02-20 12:39    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site