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authorJoel Fernandes <joelaf@google.com>2016-11-29 01:35:22 +0300
committerThomas Gleixner <tglx@linutronix.de>2016-11-29 20:02:59 +0300
commit948a5312f41658f7b76a598a139ef1f4dea09ca9 (patch)
tree18913a15606a2c42f4b0f2c041cf224df9578ef6 /include/linux
parentec4101e8903e318b9fd4e3bbf72b1eaba53c64e1 (diff)
downloadlinux-948a5312f41658f7b76a598a139ef1f4dea09ca9.tar.xz
timekeeping: Add a fast and NMI safe boot clock
This boot clock can be used as a tracing clock and will account for suspend time. To keep it NMI safe since we're accessing from tracing, we're not using a separate timekeeper with updates to monotonic clock and boot offset protected with seqlocks. This has the following minor side effects: (1) Its possible that a timestamp be taken after the boot offset is updated but before the timekeeper is updated. If this happens, the new boot offset is added to the old timekeeping making the clock appear to update slightly earlier: CPU 0 CPU 1 timekeeping_inject_sleeptime64() __timekeeping_inject_sleeptime(tk, delta); timestamp(); timekeeping_update(tk, TK_CLEAR_NTP...); (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be partially updated. Since the tk->offs_boot update is a rare event, this should be a rare occurrence which postprocessing should be able to handle. Signed-off-by: Joel Fernandes <joelaf@google.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1480372524-15181-6-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/timekeeping.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 09168c52ab64..361f8bf1429d 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -249,6 +249,7 @@ static inline u64 ktime_get_raw_ns(void)
extern u64 ktime_get_mono_fast_ns(void);
extern u64 ktime_get_raw_fast_ns(void);
+extern u64 ktime_get_boot_fast_ns(void);
/*
* Timespec interfaces utilizing the ktime based ones