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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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