sysrq: add commentary on why we use the console loglevel over using KERN_EMERG

Add an explanitory comment as to why we modify the kernel console loglevel
rather than simply moving sysrq messages to KERN_EMERG level.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index d41b9f6f7903..33a9351c896d 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -473,6 +473,12 @@ void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
         unsigned long flags;
 
         spin_lock_irqsave(&sysrq_key_table_lock, flags);
+        /*
+         * Raise the apparent loglevel to maximum so that the sysrq header
+         * is shown to provide the user with positive feedback.  We do not
+         * simply emit this at KERN_EMERG as that would change message
+         * routing in the consumers of /proc/kmsg.
+         */
         orig_log_level = console_loglevel;
         console_loglevel = 7;
         printk(KERN_INFO "SysRq : ");