John Stultz
58bfea9532
timekeeping: Fix __ktime_get_fast_ns() regression
In commit 27727df240 ("Avoid taking lock in NMI path with
CONFIG_DEBUG_TIMEKEEPING"), I changed the logic to open-code
the timekeeping_get_ns() function, but I forgot to include
the unit conversion from cycles to nanoseconds, breaking the
function's output, which impacts users like perf.
This results in bogus perf timestamps like:
swapper 0 [000] 253.427536: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426573: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426687: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426800: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426905: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427022: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427127: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427239: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427346: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427463: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 255.426572: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
Instead of more reasonable expected timestamps like:
swapper 0 [000] 39.953768: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.064839: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.175956: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.287103: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.398217: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.509324: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.620437: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.731546: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.842654: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.953772: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 41.064881: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
Add the proper use of timekeeping_delta_to_ns() to convert
the cycle delta to nanoseconds as needed.
Thanks to Brendan and Alexei for finding this quickly after
the v4.8 release. Unfortunately the problematic commit has
landed in some -stable trees so they'll need this fix as
well.
Many apologies for this mistake. I'll be looking to add a
perf-clock sanity test to the kselftest timers tests soon.
Fixes: 27727df240 "timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING"
Reported-by: Brendan Gregg <bgregg@netflix.com>
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Tested-and-reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable <stable@vger.kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1475636148-26539-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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2016-10-05 15:44:46 +02:00 |
| .. |
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alarmtimer.c
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alarmtimer: Fix comments describing structure fields
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2016-06-20 12:47:09 -07:00 |
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clockevents.c
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clockevents: Make clockevents_subsys static
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2016-07-19 10:48:06 +02:00 |
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clocksource.c
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clocksource: Defer override invalidation unless clock is unstable
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2016-08-31 14:43:33 -07:00 |
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hrtimer.c
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time: Avoid undefined behaviour in ktime_add_safe()
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2016-08-31 14:43:36 -07:00 |
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itimer.c
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jiffies.c
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Kconfig
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Makefile
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ntp.c
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ntp_internal.h
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posix-clock.c
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posix-cpu-timers.c
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posix_cpu_timer: Exit early when process has been reaped
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2016-07-11 17:20:12 +02:00 |
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posix-timers.c
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sched_clock.c
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test_udelay.c
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time: Avoid timespec in udelay_test
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2016-06-20 12:47:26 -07:00 |
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tick-broadcast-hrtimer.c
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tick/broadcast-hrtimer: Set name of the ce_broadcast_hrtimer
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2016-07-05 17:02:19 +02:00 |
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tick-broadcast.c
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tick-common.c
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tick-internal.h
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timers: Forward the wheel clock whenever possible
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2016-07-07 10:35:11 +02:00 |
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tick-oneshot.c
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tick-sched.c
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tick/nohz: Prevent stopping the tick on an offline CPU
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2016-09-13 17:53:52 +02:00 |
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tick-sched.h
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timers/nohz: Convert tick dependency mask to atomic_t
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2016-03-29 11:52:11 +02:00 |
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time.c
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time: Avoid undefined behaviour in timespec64_add_safe()
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2016-08-31 14:43:35 -07:00 |
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timeconst.bc
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timeconv.c
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time: Add time64_to_tm()
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2016-06-20 12:47:15 -07:00 |
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timecounter.c
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timekeeping.c
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timekeeping: Fix __ktime_get_fast_ns() regression
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2016-10-05 15:44:46 +02:00 |
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timekeeping.h
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timekeeping_debug.c
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timekeeping: Prints the amounts of time spent during suspend
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2016-08-31 14:43:34 -07:00 |
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timekeeping_internal.h
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timer.c
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timers: Fix get_next_timer_interrupt() computation
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2016-08-09 09:31:55 +02:00 |
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timer_list.c
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timer_stats.c
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timer: Avoid using timespec
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2016-06-20 12:47:33 -07:00 |