tracing: Unify the "boot" and "mono" tracing clocks

Unify the "boot" and "mono" tracing clocks and document the new behaviour.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20180301165150.489635255@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 4 insertions, 18 deletions

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index d4601df6e72e..bf89f98bfdb9 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -449,17 +449,9 @@ of ftrace. Here is a list of some of the key files:
                 which is montonic but is not subject to any rate adjustments
                 and ticks at the same rate as the hardware clocksource.
 
-          boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
-                fast monotonic clock, but also accounts for time spent in
-                suspend. Since the clock access is designed for use in
-                tracing in the suspend path, some side effects are possible
-                if clock is accessed after the suspend time is accounted before
-                the fast mono clock is updated. In this case, the clock update
-                appears to happen slightly sooner than it normally would have.
-                Also on 32-bit systems, it's possible that the 64-bit boot offset
-                sees a partial update. These effects are rare and post
-                processing should be able to handle them. See comments in the
-                ktime_get_boot_fast_ns() function for more information.
+          boot: Same as mono. Used to be a separate clock which accounted
+                for the time spent in suspend while CLOCK_MONOTONIC did
+                not.
 
         To set a clock, simply echo the clock name into this file.
 
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index abb396731332..82c219dfd3bb 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -113,12 +113,6 @@ extern u64 ktime_get_mono_fast_ns(void);
 extern u64 ktime_get_raw_fast_ns(void);
 extern u64 ktime_get_real_fast_ns(void);
 
-/* Clock BOOTTIME compatibility wrappers */
-static inline u64 ktime_get_boot_fast_ns(void)
-{
-        return ktime_get_mono_fast_ns();
-}
-
 /*
  * timespec64 interfaces utilizing the ktime based ones
  */
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 20a2300ae4e8..300f4ea39646 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1164,7 +1164,7 @@ static struct {
         { trace_clock,                  "perf",         1 },
         { ktime_get_mono_fast_ns,       "mono",         1 },
         { ktime_get_raw_fast_ns,        "mono_raw",     1 },
-        { ktime_get_boot_fast_ns,       "boot",         1 },
+        { ktime_get_mono_fast_ns,       "boot",         1 },
         ARCH_TRACE_CLOCKS
 };