linux-kernel - [PATCH] printk: add KERN_NOTIME to skip the timestamp

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Date:   Wed, 13 Feb 2019 02:11:05 +0800
From:   Xiang Xiao <xiaoxiang781216@...il.com>
To:     pmladek@...e.com, sergey.senozhatsky@...il.com,
        rostedt@...dmis.org, linux-kernel@...r.kernel.org
Cc:     Xiang Xiao <xiaoxiang@...omi.com>
Subject: [PATCH] printk: add KERN_NOTIME to skip the timestamp

Because log may already add the timestamp sometime

Signed-off-by: Xiang Xiao <xiaoxiang@...omi.com>
---
 include/linux/kern_levels.h | 2 ++
 include/linux/printk.h      | 1 +
 kernel/printk/printk.c      | 7 ++++++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/kern_levels.h b/include/linux/kern_levels.h
index d237fe8..ed2aec6 100644
--- a/include/linux/kern_levels.h
+++ b/include/linux/kern_levels.h
@@ -23,6 +23,8 @@
  */
 #define KERN_CONT	KERN_SOH "c"
 
+#define KERN_NOTIME	KERN_SOH "t"	/* don't print the timestamp */
+
 /* integer equivalents of KERN_<LEVEL> */
 #define LOGLEVEL_SCHED		-2	/* Deferred messages from sched code
 					 * are set to this special level */
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 77740a5..be12ac4 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -20,6 +20,7 @@ static inline int printk_get_level(const char *buffer)
 		case '0' ... '7':
 		case 'd':	/* KERN_DEFAULT */
 		case 'c':	/* KERN_CONT */
+		case 't':	/* KERN_NOTIME */
 			return buffer[1];
 		}
 	}
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d3d1703..0688cf2 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -346,6 +346,7 @@ enum log_flags {
 	LOG_NEWLINE	= 2,	/* text ended with a newline */
 	LOG_PREFIX	= 4,	/* text started with a prefix */
 	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
+	LOG_NOTIME	= 16,	/* don't print the timestamp */
 };
 
 struct printk_log {
@@ -1247,7 +1248,7 @@ static size_t print_prefix(const struct printk_log *msg, bool syslog,
 
 	if (syslog)
 		len = print_syslog((msg->facility << 3) | msg->level, buf);
-	if (time)
+	if (time && !(msg->flags & LOG_NOTIME))
 		len += print_time(msg->ts_nsec, buf + len);
 	return len;
 }
@@ -1873,6 +1874,10 @@ int vprintk_store(int facility, int level,
 				break;
 			case 'c':	/* KERN_CONT */
 				lflags |= LOG_CONT;
+				break;
+			case 't':	/* KERN_NOTIME */
+				lflags |= LOG_NOTIME;
+				break;
 			}
 
 			text_len -= 2;
-- 
2.7.4