printk: flush conflicting continuation line

An earlier newline was missing and current print is from different task.
In this scenario flush the continuation line and store this line
seperatly.

This patch fix the below scenario of timestamp interleaving,
   [   28.154370 ] read_word_reg : reg[0x 3], reg[0x 4]  data [0x 642]
   [   28.155428 ] uart disconnect
   [   31.947341 ] dvfs[cpufreq.c<275>]:plug-in cpu<1> done
   [   28.155445 ] UART detached : send switch state 201
   [   32.014112 ] read_reg : reg[0x 3] data[0x21]

[akpm@linux-foundation.org: simplify and condense the code]
Signed-off-by: Arun KS <getarunks@gmail.com>
Signed-off-by: Arun KS <arun.ks@broadcom.com>
Cc: Joe Perches <joe@perches.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f8b41bddc6dc..b1d255f04135 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1595,10 +1595,13 @@ asmlinkage int vprintk_emit(int facility, int level,
                  * either merge it with the current buffer and flush, or if
                  * there was a race with interrupts (prefix == true) then just
                  * flush it out and store this line separately.
+                 * If the preceding printk was from a different task and missed
+                 * a newline, flush and append the newline.
                  */
-                if (cont.len && cont.owner == current) {
-                        if (!(lflags & LOG_PREFIX))
-                                stored = cont_add(facility, level, text, text_len);
+                if (cont.len) {
+                        if (cont.owner == current && !(lflags & LOG_PREFIX))
+                                stored = cont_add(facility, level, text,
+                                                  text_len);
                         cont_flush(LOG_NEWLINE);
                 }