printk: suppress empty continuation lines

We have a fairly common pattern where you print several things as continuations on one single line in a loop, and then at the end you do printk(KERN_CONT "\n"); to flush the buffered output. But if the output was flushed by something else (concurrent printk activity, or just system logging), we don't want that final flushing to just print an empty line. So just suppress empty continuation lines when they couldn't be merged into the line they are a continuation of. Signed-off-by: Linus Torvalds <[email protected]>
cluon · Oct 19, 2016 · 8835ca5 · 8835ca5
1 parent 63ae602
commit 8835ca5
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
@@ -1769,6 +1769,10 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
 		cont_flush();
 	}
 
+	/* Skip empty continuation lines that couldn't be added - they just flush */
+	if (!text_len && (lflags & LOG_CONT))
+		return 0;
+
 	/* If it doesn't end in a newline, try to buffer the current line */
 	if (!(lflags & LOG_NEWLINE)) {
 		if (cont_add(facility, level, lflags, text, text_len))