console: prevent registered consoles from dumping old kernel message over again
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.
As suggested by Andrew Morton, every time a new console is registered, it
will be set as the "exclusive" console which will dump the already
existing kernel messages.
Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/printk.c b/kernel/printk.c
index 2b591f2..a53607e 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -113,6 +113,11 @@
static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
/*
+ * If exclusive_console is non-NULL then only this console is to be printed to.
+ */
+static struct console *exclusive_console;
+
+/*
* Array of consoles built from command line options (console=)
*/
struct console_cmdline
@@ -476,6 +481,8 @@
struct console *con;
for_each_console(con) {
+ if (exclusive_console && con != exclusive_console)
+ continue;
if ((con->flags & CON_ENABLED) && con->write &&
(cpu_online(smp_processor_id()) ||
(con->flags & CON_ANYTIME)))
@@ -1230,6 +1237,11 @@
local_irq_restore(flags);
}
console_locked = 0;
+
+ /* Release the exclusive_console once it is used */
+ if (unlikely(exclusive_console))
+ exclusive_console = NULL;
+
up(&console_sem);
spin_unlock_irqrestore(&logbuf_lock, flags);
if (wake_klogd)
@@ -1464,6 +1476,12 @@
spin_lock_irqsave(&logbuf_lock, flags);
con_start = log_start;
spin_unlock_irqrestore(&logbuf_lock, flags);
+ /*
+ * We're about to replay the log buffer. Only do this to the
+ * just-registered console to avoid excessive message spam to
+ * the already-registered consoles.
+ */
+ exclusive_console = newcon;
}
console_unlock();
console_sysfs_notify();
