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Subject[PATCH] console: prevent registered consoles from dumping old kernel message over again
Date
For a platform with many consoles like:
"console=tty1 console=ttyMFD2 console=ttyS0 earlyprintk=mrst"

Each time when the non "selected_console" (tty1 and ttyMFD2 here) get
registered, the existing kernel message will be printed out on registered
consoles again, the "mrst" early console will get some same message for
3 times, and "tty1" will get some for twice.

So try to temporarily disable registered console's printing when dump the
existing kernel messages to the new console.

Signed-off-by: Feng Tang <feng.tang@intel.com>
---
kernel/printk.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index f64b899..ba7186b 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1245,6 +1245,7 @@ void register_console(struct console *newcon)
int i;
unsigned long flags;
struct console *bcon = NULL;
+ struct console *con;

/*
* before we register a new CON_BOOT console, make sure we don't
@@ -1357,8 +1358,20 @@ void register_console(struct console *newcon)
spin_lock_irqsave(&logbuf_lock, flags);
con_start = log_start;
spin_unlock_irqrestore(&logbuf_lock, flags);
+
+ /*
+ * Disable the existing consoles temporarily to prevent it from
+ * printing out kernel log again.
+ */
+ for_each_console(con)
+ if (con != newcon)
+ con->flags &= ~CON_ENABLED;
}
release_console_sem();
+
+ for_each_console(con)
+ con->flags |= CON_ENABLED;
+
console_sysfs_notify();

/*
--
1.7.0.4


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