diff options
Diffstat (limited to 'sysdeps/unix/i386/i586/clock_gettime.c')
| -rw-r--r-- | sysdeps/unix/i386/i586/clock_gettime.c | 47 |
1 files changed, 39 insertions, 8 deletions
diff --git a/sysdeps/unix/i386/i586/clock_gettime.c b/sysdeps/unix/i386/i586/clock_gettime.c index 85dcdcfe68..5e28370acf 100644 --- a/sysdeps/unix/i386/i586/clock_gettime.c +++ b/sysdeps/unix/i386/i586/clock_gettime.c @@ -19,6 +19,9 @@ #include <time.h> #include <libc-internal.h> +#include "cpuclock-init.h" + + /* This implementation uses the TSC register in modern (i586 and up) IA-32 processors (most modern clones also provide it). Since we need the resolution of the clock and since determining this is not cheap, we @@ -33,17 +36,42 @@ static unsigned long long int freq; -/* We add an limitation here: we assume that the machine is not up as - long as it takes to wrap-around the 64-bit timestamp counter. On a - 4GHz machine it would take 136 years of uptime to wrap around so - this "limitation" is not severe. +/* We need the starting time for the process. */ +CPUCLOCK_VARDECL (_dl_cpuclock_offset); + + +/* This function is defined in the thread library. */ +extern int __pthread_clock_gettime (unsigned long long int freq, + struct timespec *tp) + __attribute__ ((__weak__)); + - We use this clock also as the monotonic clock since we don't allow - setting the CPU-time clock. If this should ever change we will have - to separate the two. */ +/* We add an limitation here: we assume that the process is not + running as long as it takes to wrap-around the 64-bit timestamp + counter. On a 4GHz machine it would take 136 years of uptime to + wrap around so this "limitation" is not severe. */ #define EXTRA_CLOCK_CASES \ - case CLOCK_PROCESS_CPUTIME_ID: \ case CLOCK_THREAD_CPUTIME_ID: \ + if (__pthread_clock_gettime != NULL) \ + { \ + if (__builtin_expect (freq == 0, 0)) \ + { \ + /* This can only happen if we haven't initialized the `freq' \ + variable yet. Do this now. We don't have to protect this \ + code against multiple execution since all of them should \ + lead to the same result. */ \ + freq = __get_clockfreq (); \ + if (__builtin_expect (freq == 0, 0)) \ + /* Something went wrong. */ \ + break; \ + } \ + \ + retval = __pthread_clock_gettime (freq, tp); \ + break; \ + } \ + /* FALLTHROUGH */ \ + \ + case CLOCK_PROCESS_CPUTIME_ID: \ { \ unsigned long long int tsc; \ \ @@ -62,6 +90,9 @@ static unsigned long long int freq; /* Get the current counter. */ \ asm volatile ("rdtsc" : "=A" (tsc)); \ \ + /* Compute the offset since the start time of the process. */ \ + tsc -= _dl_cpuclock_offset; \ + \ /* Compute the seconds. */ \ tp->tv_sec = tsc / freq; \ \ |