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| author | Matt Helsley <matthltc@us.ibm.com> | 2005-12-12 00:37:09 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-12-12 08:57:42 -0800 |
| commit | 64123fd42c7a1e4ebf6acd2399c98caddc7e0c26 (patch) | |
| tree | d6b1794fa33287d145a44ab55bc2e2ef65ebf248 /kernel | |
| parent | 894ec8707ced240b96dc45944790fb35d9a6b03c (diff) | |
| download | linux-64123fd42c7a1e4ebf6acd2399c98caddc7e0c26.tar.gz | |
[PATCH] Add getnstimestamp function
There are several functions that might seem appropriate for a timestamp: get_cycles() current_kernel_time() do_gettimeofday() <read jiffies/jiffies_64> Each has problems with combinations of SMP-safety, low resolution, and monotonicity. This patch adds a new function that returns a monotonic SMP-safe timestamp with nanosecond resolution where available. Changes: Split timestamp into separate patch Moved to kernel/time.c Renamed to getnstimestamp Fixed unintended-pointer-arithmetic bug Signed-off-by: Matt Helsley <matthltc@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/time.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/time.c b/kernel/time.c index 245d595a13cb..b94bfa8c03e0 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -561,6 +561,28 @@ void getnstimeofday(struct timespec *tv) EXPORT_SYMBOL_GPL(getnstimeofday); #endif +void getnstimestamp(struct timespec *ts) +{ + unsigned int seq; + struct timespec wall2mono; + + /* synchronize with settimeofday() changes */ + do { + seq = read_seqbegin(&xtime_lock); + getnstimeofday(ts); + wall2mono = wall_to_monotonic; + } while(unlikely(read_seqretry(&xtime_lock, seq))); + + /* adjust to monotonicaly-increasing values */ + ts->tv_sec += wall2mono.tv_sec; + ts->tv_nsec += wall2mono.tv_nsec; + while (unlikely(ts->tv_nsec >= NSEC_PER_SEC)) { + ts->tv_nsec -= NSEC_PER_SEC; + ts->tv_sec++; + } +} +EXPORT_SYMBOL_GPL(getnstimestamp); + #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) { |