From 64123fd42c7a1e4ebf6acd2399c98caddc7e0c26 Mon Sep 17 00:00:00 2001 From: Matt Helsley Date: Mon, 12 Dec 2005 00:37:09 -0800 Subject: [PATCH] [PATCH] Add getnstimestamp function There are several functions that might seem appropriate for a timestamp: get_cycles() current_kernel_time() do_gettimeofday() 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/time.h | 1 + kernel/time.c | 22 ++++++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/include/linux/time.h b/include/linux/time.h index bfbe92d076..797ccd813b 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -95,6 +95,7 @@ struct itimerval; extern int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue); extern int do_getitimer(int which, struct itimerval *value); extern void getnstimeofday (struct timespec *tv); +extern void getnstimestamp(struct timespec *ts); extern struct timespec timespec_trunc(struct timespec t, unsigned gran); diff --git a/kernel/time.c b/kernel/time.c index 245d595a13..b94bfa8c03 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) { -- 2.39.5