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[PATCH 0/2 v8] printk: Add new timestamps

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  [PATCH 0/2 v8] printk: Add new timestamps Prarit Bhargava <prarit@redhat.com> - 2017-08-24 15:50 +0200
    [PATCH 1/2 v8] time: Make fast functions return 0 before timekeeping is initialized Prarit Bhargava <prarit@redhat.com> - 2017-08-24 15:50 +0200

#1719256 — [PATCH 0/2 v8] printk: Add new 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 in real time.

Add monotonic, boottime, and real clock timestamps in addition to the existing
local hardware clock timestamp.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Christoffer Dall <cdall@linaro.org>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: linux-doc@vger.kernel.org
[jstultz: reworked Kconfig settings to avoid defconfig noise]
Signed-off-by: John Stultz <john.stultz@linaro.org>

Prarit Bhargava (2):
  time: Make fast functions return 0 before timekeeping is initialized
  printk: Add monotonic, boottime, and realtime timestamps

 Documentation/admin-guide/kernel-parameters.txt |   6 +-
 include/linux/timekeeping.h                     |   1 +
 kernel/printk/printk.c                          | 154 +++++++++++++++++++++++-
 kernel/time/timekeeping.c                       |  46 +++++--
 lib/Kconfig.debug                               |  65 +++++++++-
 5 files changed, 253 insertions(+), 19 deletions(-)

-- 
1.8.5.5

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#1719258 — [PATCH 1/2 v8] time: Make fast functions return 0 before timekeeping is initialized

printk timestamps will be extended to include mono and boot time by using
the fast timekeeping functions ktime_get_mono|boot_fast_ns() functions.
The functions can return garbage before timekeeping is initialized
resulting in garbage timestamps.

The fast time functions must return 0 before timekeeping is initialized.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@codeaurora.org>
---
 kernel/time/timekeeping.c | 47 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 33 insertions(+), 14 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index cedafa008de5..d111039e0245 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -60,8 +60,39 @@ struct tk_fast {
 	struct tk_read_base	base[2];
 };
 
-static struct tk_fast tk_fast_mono ____cacheline_aligned;
-static struct tk_fast tk_fast_raw  ____cacheline_aligned;
+/* Suspend-time cycles value for halted fast timekeeper. */
+static u64 cycles_at_suspend;
+
+static u64 dummy_clock_read(struct clocksource *cs)
+{
+	return cycles_at_suspend;
+}
+
+static struct clocksource dummy_clock = {
+	.read = dummy_clock_read,
+};
+
+static struct tk_fast tk_fast_mono ____cacheline_aligned = {
+	.base = {
+		(struct tk_read_base){
+			.clock = &dummy_clock,
+		},
+		(struct tk_read_base){
+			.clock = &dummy_clock,
+		},
+	},
+};
+
+static struct tk_fast tk_fast_raw  ____cacheline_aligned = {
+	.base = {
+		(struct tk_read_base){
+			.clock = &dummy_clock,
+		},
+		(struct tk_read_base){
+			.clock = &dummy_clock,
+		},
+	},
+};
 
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
@@ -477,18 +508,6 @@ u64 notrace ktime_get_boot_fast_ns(void)
 }
 EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
 
-/* Suspend-time cycles value for halted fast timekeeper. */
-static u64 cycles_at_suspend;
-
-static u64 dummy_clock_read(struct clocksource *cs)
-{
-	return cycles_at_suspend;
-}
-
-static struct clocksource dummy_clock = {
-	.read = dummy_clock_read,
-};
-
 /**
  * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.
  * @tk: Timekeeper to snapshot.
-- 
1.8.5.5

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