From: Karel Zak <kzak@redhat.com>
Date: Thu, 12 Mar 2026 12:22:55 +0000 (+0100)
Subject: dmesg: warn on boot time failure instead of suppressing timestamps
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7b35816ab92e2ea01fb334199165bb6b7b9d09a2;p=thirdparty%2Futil-linux.git

dmesg: warn on boot time failure instead of suppressing timestamps

When dmesg_get_boot_time() fails, warn the user instead of silently
adding DMESG_TIMEFTM_NONE to suppress all timestamp output. The user
asked for a specific format and should get it, with a warning that
wall-clock timestamps may be inaccurate.

Also move the boot time check after the time format post-processing
so it operates on the final resolved format list, and add
DMESG_TIMEFTM_CTIME_DELTA to the condition since it also requires
boot time.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index 1440dd4e4..419077178 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -1889,17 +1889,6 @@ int main(int argc, char *argv[])
 		nopager = 1;
 	}
 
-	if ((is_time_fmt_set(&ctl, DMESG_TIMEFTM_RELTIME) ||
-	     is_time_fmt_set(&ctl, DMESG_TIMEFTM_CTIME)   ||
-	     is_time_fmt_set(&ctl, DMESG_TIMEFTM_ISO8601)) ||
-	     ctl.since ||
-	     ctl.until) {
-		if (dmesg_get_boot_time(&ctl.boot_time) != 0)
-			include_time_fmt(&ctl, DMESG_TIMEFTM_NONE);
-		else
-			ctl.suspended_time = dmesg_get_suspended_time();
-	}
-
 	/*
 	 * Resolve NONE (--notime) vs. delta combinations. When both are
 	 * specified (e.g. -d -t), delta wins and timestamp is suppressed.
@@ -1934,6 +1923,20 @@ int main(int argc, char *argv[])
 					  DMESG_TIMEFTM_CTIME, DMESG_TIMEFTM_CTIME_DELTA);
 	}
 
+	/* Boot time is needed for wall-clock timestamp formats */
+	if ((is_time_fmt_set(&ctl, DMESG_TIMEFTM_RELTIME)     ||
+	     is_time_fmt_set(&ctl, DMESG_TIMEFTM_CTIME)       ||
+	     is_time_fmt_set(&ctl, DMESG_TIMEFTM_CTIME_DELTA) ||
+	     is_time_fmt_set(&ctl, DMESG_TIMEFTM_ISO8601))    ||
+	     ctl.since ||
+	     ctl.until) {
+		if (dmesg_get_boot_time(&ctl.boot_time) != 0)
+			warnx(_("failed to determine boot time, "
+				"timestamps will be inaccurate"));
+		else
+			ctl.suspended_time = dmesg_get_suspended_time();
+	}
+
 	if (!ctl.json)
 		ctl.color = colors_init(colormode, "dmesg") ? 1 : 0;
 	if (ctl.follow)