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由 Joel Fernandes 提交于
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: NJoel Fernandes <joelaf@google.com> Signed-off-by: NJohn Stultz <john.stultz@linaro.org> Reviewed-by: NThomas 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.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
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