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| author |   Heiko Carstens <heiko.carstens@de.ibm.com> | 2009-09-11 10:28:31 +0200 |
|---|---|---|
| committer |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-09-11 10:29:42 +0200 |
| commit | 05e7ff7da78bad3edc1290ed86b4a37da72ced62 (patch) | |
| tree | f7348a9f4f561a53465abea731c2ef59900fd62f /arch | |
| parent | [S390] dasd: fix message naming (diff) | |
| download | linux-dev-05e7ff7da78bad3edc1290ed86b4a37da72ced62.tar.xz linux-dev-05e7ff7da78bad3edc1290ed86b4a37da72ced62.zip | |
[S390] introduce get_clock_monotonic
Introduce get_clock_monotonic() function which can be used to get a
(fast) timestamp. Resolution is the same as for get_clock(). The
only difference is that the timestamps are monotonic and don't jump
backward or forward.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/include/asm/timex.h | 14 | ||||
| -rw-r--r-- | arch/s390/kernel/time.c | 3 |
2 files changed, 16 insertions, 1 deletions
diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h index cc21e3e20fd7..24aa1cda20ad 100644 --- a/arch/s390/include/asm/timex.h +++ b/arch/s390/include/asm/timex.h @@ -90,4 +90,18 @@ unsigned long long monotonic_clock(void); extern u64 sched_clock_base_cc; +/** + * get_clock_monotonic - returns current time in clock rate units + * + * The caller must ensure that preemption is disabled. + * The clock and sched_clock_base get changed via stop_machine. + * Therefore preemption must be disabled when calling this + * function, otherwise the returned value is not guaranteed to + * be monotonic. + */ +static inline unsigned long long get_clock_monotonic(void) +{ + return get_clock_xt() - sched_clock_base_cc; +} + #endif diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index d4c8e9c47c81..54e327e9af04 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -60,6 +60,7 @@ #define TICK_SIZE tick u64 sched_clock_base_cc = -1; /* Force to data section. */ +EXPORT_SYMBOL_GPL(sched_clock_base_cc); static DEFINE_PER_CPU(struct clock_event_device, comparators); @@ -68,7 +69,7 @@ static DEFINE_PER_CPU(struct clock_event_device, comparators); */ unsigned long long notrace sched_clock(void) { - return ((get_clock_xt() - sched_clock_base_cc) * 125) >> 9; + return (get_clock_monotonic() * 125) >> 9; } /* |