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| author | Fabio M. Di Nitto <fdinitto@redhat.com> | 2011-03-22 16:34:20 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-22 17:44:12 -0700 |
| commit | 7bf693951a8e5f7e600a45b74d91d962a453146e (patch) | |
| tree | d322e17d0d6b445d8332e210e01d3cce7ddfe5ca /kernel/printk.c | |
| parent | 26297607e09ca6c7e6f2a6b86a8bee2f23503bb8 (diff) | |
| download | lwn-7bf693951a8e5f7e600a45b74d91d962a453146e.tar.gz lwn-7bf693951a8e5f7e600a45b74d91d962a453146e.zip | |
console: allow to retain boot console via boot option keep_bootcon
On some architectures, the boot process involves de-registering the boot
console (early boot), initialize drivers and then re-register the console.
This mechanism introduces a window in which no printk can happen on the
console and messages are buffered and then printed once the new console is
available.
If a kernel crashes during this window, all it's left on the boot console
is "console [foo] enabled, bootconsole disabled" making debug of the crash
rather 'interesting'.
By adding "keep_bootcon" option, do not unregister the boot console, that
will allow to printk everything that is happening up to the crash.
The option is clearly meant only for debugging purposes as it introduces
lots of duplicated info printed on console, but will make bug report from
users easier as it doesn't require a kernel build just to figure out where
we crash.
Signed-off-by: Fabio M. Di Nitto <fabbione@fabbione.net>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/printk.c')
| -rw-r--r-- | kernel/printk.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index 33284adb2189..2b591f252e55 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1316,6 +1316,18 @@ void console_start(struct console *console) } EXPORT_SYMBOL(console_start); +static int __read_mostly keep_bootcon; + +static int __init keep_bootcon_setup(char *str) +{ + keep_bootcon = 1; + printk(KERN_INFO "debug: skip boot console de-registration.\n"); + + return 0; +} + +early_param("keep_bootcon", keep_bootcon_setup); + /* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to @@ -1463,7 +1475,9 @@ void register_console(struct console *newcon) * users know there might be something in the kernel's log buffer that * went to the bootconsole (that they do not see on the real console) */ - if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) { + if (bcon && + ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) && + !keep_bootcon) { /* we need to iterate through twice, to make sure we print * everything out, before we unregister the console(s) */ |