[tip:core/printk] printk: Add monotonic, boottime, and realtime timestamps
From: tip-bot for Prarit Bhargava
Date: Mon Sep 25 2017 - 15:31:09 EST
Commit-ID: a4c1a0002f4518363da9d9ecd7b805af152dcdf1
Gitweb: http://git.kernel.org/tip/a4c1a0002f4518363da9d9ecd7b805af152dcdf1
Author: Prarit Bhargava <prarit@xxxxxxxxxx>
AuthorDate: Mon, 28 Aug 2017 08:21:54 -0400
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 25 Sep 2017 21:12:06 +0200
printk: Add monotonic, boottime, and realtime timestamps
printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
timestamp to printk messages. The local hardware clock loses time each
day making it difficult to determine exactly when an issue has occurred in
the kernel log, and making it difficult to determine how kernel and
hardware issues relate to each other.
Make printk output different timestamps by adding options for no timestamp,
the local hardware clock, the monotonic clock, the boottime clock, and the
clock realtime. The default clock can be selected via:
- Kconfig
- Kernel command line parameter
- Sysfs file
Note, that existing user space tools might be confused by selecting clock
realtime, so handle with care.
[ jstultz: Reworked Kconfig settings to avoid defconfig noise ]
Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Joel Fernandes <joelaf@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Deepa Dinamani <deepa.kernel@xxxxxxxxx>
Cc: Christoffer Dall <cdall@xxxxxxxxxx>
Cc: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Cc: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
Cc: Olof Johansson <olof@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1503922914-10660-3-git-send-email-prarit@xxxxxxxxxx
---
Documentation/admin-guide/kernel-parameters.txt | 6 +-
kernel/printk/printk.c | 116 +++++++++++++++++++++++-
lib/Kconfig.debug | 48 +++++++++-
3 files changed, 162 insertions(+), 8 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0549662..9a84483 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3211,8 +3211,10 @@
ratelimit - ratelimit the logging
Default: ratelimit
- printk.time= Show timing data prefixed to each printk message line
- Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+ printk.time= Show timestamp prefixed to each printk message line
+ Format: <string>
+ (0/N/n/disable, 1/Y/y/local,
+ b/boot, m/monotonic, r/realtime (in UTC))
processor.max_cstate= [HW,ACPI]
Limit processor to maximum C-state
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 512f7c2..4b824dd 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -576,6 +576,9 @@ static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
}
+static u64 printk_get_first_ts(void);
+static u64 (*printk_get_ts)(void) = printk_get_first_ts;
+
/* insert record into the buffer, discard old ones, update heads */
static int log_store(int facility, int level,
enum log_flags flags, u64 ts_nsec,
@@ -624,7 +627,7 @@ static int log_store(int facility, int level,
if (ts_nsec > 0)
msg->ts_nsec = ts_nsec;
else
- msg->ts_nsec = local_clock();
+ msg->ts_nsec = printk_get_ts();
memset(log_dict(msg) + dict_len, 0, pad_len);
msg->len = size;
@@ -1201,14 +1204,116 @@ static inline void boot_delay_msec(int level)
}
#endif
-static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
-module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
+/**
+ * enum timestamp_sources - Timestamp sources for printk() messages.
+ * @PRINTK_TIME_DISABLED: No time stamp.
+ * @PRINTK_TIME_LOCAL: Local hardware clock timestamp.
+ * @PRINTK_TIME_BOOT: Boottime clock timestamp.
+ * @PRINTK_TIME_MONO: Monotonic clock timestamp.
+ * @PRINTK_TIME_REAL: Realtime clock timestamp. On 32-bit
+ * systems selecting the real clock printk timestamp may lead to unlikely
+ * situations where a timestamp is wrong because the real time offset is read
+ * without the protection of a sequence lock.
+ */
+enum timestamp_sources {
+ PRINTK_TIME_DISABLED = 0,
+ PRINTK_TIME_LOCAL = 1,
+ PRINTK_TIME_BOOT = 2,
+ PRINTK_TIME_MONO = 3,
+ PRINTK_TIME_REAL = 4,
+};
+
+static const char * const timestamp_sources_str[5] = {
+ "disabled",
+ "local",
+ "boottime",
+ "monotonic",
+ "realtime",
+};
+
+static int printk_time = CONFIG_PRINTK_TIME_TYPE;
+
+static void printk_set_ts_func(void)
+{
+ switch (printk_time) {
+ case PRINTK_TIME_LOCAL:
+ case PRINTK_TIME_DISABLED:
+ default:
+ printk_get_ts = local_clock;
+ break;
+ case PRINTK_TIME_BOOT:
+ printk_get_ts = ktime_get_boot_fast_ns;
+ break;
+ case PRINTK_TIME_MONO:
+ printk_get_ts = ktime_get_mono_fast_ns;
+ break;
+ case PRINTK_TIME_REAL:
+ printk_get_ts = ktime_get_real_fast_ns;
+ break;
+ }
+}
+
+static u64 printk_get_first_ts(void)
+{
+ printk_set_ts_func();
+ return printk_get_ts();
+}
+
+static int param_set_time(const char *val, const struct kernel_param *kp)
+{
+ char *param = strstrip((char *)val);
+ int _printk_time = -1;
+ int ts;
+
+ if (strlen(param) == 1) {
+ /* Preserve legacy boolean settings */
+ if ((param[0] == '0') || (param[0] == 'n') ||
+ (param[0] == 'N'))
+ _printk_time = PRINTK_TIME_DISABLED;
+ if ((param[0] == '1') || (param[0] == 'y') ||
+ (param[0] == 'Y'))
+ _printk_time = PRINTK_TIME_LOCAL;
+ }
+ if (_printk_time == -1) {
+ for (ts = 0; ts < ARRAY_SIZE(timestamp_sources_str); ts++) {
+ if (!strncmp(timestamp_sources_str[ts], param,
+ strlen(param))) {
+ _printk_time = ts;
+ break;
+ }
+ }
+ }
+ if (_printk_time == -1) {
+ pr_warn("printk: invalid timestamp option %s\n", param);
+ return -EINVAL;
+ }
+
+ printk_time = _printk_time;
+ if (printk_time > PRINTK_TIME_DISABLED)
+ printk_set_ts_func();
+
+ pr_info("printk: timestamp set to %s\n",
+ timestamp_sources_str[printk_time]);
+ return 0;
+}
+
+static int param_get_time(char *buffer, const struct kernel_param *kp)
+{
+ return scnprintf(buffer, PAGE_SIZE, "%s",
+ timestamp_sources_str[printk_time]);
+}
+
+static struct kernel_param_ops printk_time_ops = {
+ .set = param_set_time,
+ .get = param_get_time,
+};
+module_param_cb(time, &printk_time_ops, NULL, 0644);
static size_t print_time(u64 ts, char *buf)
{
unsigned long rem_nsec;
- if (!printk_time)
+ if (printk_time == PRINTK_TIME_DISABLED)
return 0;
rem_nsec = do_div(ts, 1000000000);
@@ -1631,7 +1736,7 @@ static bool cont_add(int facility, int level, enum log_flags flags, const char *
cont.facility = facility;
cont.level = level;
cont.owner = current;
- cont.ts_nsec = local_clock();
+ cont.ts_nsec = printk_get_ts();
cont.flags = flags;
}
@@ -1861,6 +1966,7 @@ static size_t msg_print_text(const struct printk_log *msg,
bool syslog, char *buf, size_t size) { return 0; }
static bool suppress_message_printing(int level) { return false; }
+static int printk_time;
#endif /* CONFIG_PRINTK */
#ifdef CONFIG_EARLY_PRINTK
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2689b7c..b1602fb 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -8,12 +8,58 @@ config PRINTK_TIME
messages to be added to the output of the syslog() system
call and at the console.
+choice
+ prompt "printk default clock timestamp" if PRINTK_TIME
+ default PRINTK_TIME_LOCAL if PRINTK_TIME
+ help
+ This option is selected by setting one of
+ PRINTK_TIME_[DISABLE|LOCAL|BOOT|MONO|REAL] and causes time stamps of
+ the printk() messages to be added to the output of the syslog()
+ system call and at the console.
+
The timestamp is always recorded internally, and exported
to /dev/kmsg. This flag just specifies if the timestamp should
be included, not that the timestamp is recorded.
The behavior is also controlled by the kernel command line
- parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
+ parameter printk.time. See
+ Documentation/admin-guide/kernel-parameters.rst
+
+config PRINTK_TIME_LOCAL
+ bool "Local Clock"
+ help
+ Selecting this option causes the time stamps of printk() to be
+ stamped with the unadjusted hardware clock.
+
+config PRINTK_TIME_BOOT
+ bool "CLOCK_BOOTTIME"
+ help
+ Selecting this option causes the time stamps of printk() to be
+ stamped with the adjusted boottime clock.
+
+config PRINTK_TIME_MONO
+ bool "CLOCK_MONOTONIC"
+ help
+ Selecting this option causes the time stamps of printk() to be
+ stamped with the adjusted monotonic clock.
+
+config PRINTK_TIME_REAL
+ bool "CLOCK_REALTIME"
+ help
+ Selecting this option causes the time stamps of printk() to be
+ stamped with the adjusted realtime clock (UTC).
+endchoice
+
+config PRINTK_TIME_TYPE
+ int
+ depends on PRINTK
+ range 0 4
+ default 0 if !PRINTK_TIME
+ default 1 if PRINTK_TIME_LOCAL
+ default 2 if PRINTK_TIME_BOOT
+ default 3 if PRINTK_TIME_MONO
+ default 4 if PRINTK_TIME_REAL
+
config CONSOLE_LOGLEVEL_DEFAULT
int "Default console loglevel (1-15)"