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printk: don't prefer unsuited consoles on registration

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console election: If some console happens to be registered first which does
not provide a tty binding (!console->device), it prevents that more suited
consoles which are registered later on can enter the candidate pool for
console_device().  This is observable with KGDB's console which may already
be registered (and exploited!) during early debugger connections, that is
before any regular console registration.

This patch fixes the issue by postponing the final, automated
preferred_console selection until someone with a non-NULL device handler
comes around.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Gerd Hoffmann <kraxel@suse.de>
Cc: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Jan Kiszka 2008-05-12 21:21:04 +02:00 committed by Thomas Gleixner
parent 3b8945e8d4
commit cd3a1b8562
1 changed files with 5 additions and 2 deletions
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7
kernel/printk.c
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@ -1157,8 +1157,11 @@ void register_console(struct console *console)
console->index = 0;
if (console->setup == NULL ||
console->setup(console, NULL) == 0) {
console->flags |= CON_ENABLED | CON_CONSDEV;
preferred_console = 0;
console->flags |= CON_ENABLED;
if (console->device) {
console->flags |= CON_CONSDEV;
preferred_console = 0;
}
}
}