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c4c94ea0ac
The problem from a user point of view was that on Solaris the time related functions (e.g. NOW(), SYSDATE(), etc) would always return a fixed time. This bug was happening due to a logic in the time retrieving wrapper function which would only call the time() function every half second. This interval between calls would be calculated using the gethrtime() and the logic relied on the fact that time returned by it is monotonic. Unfortunately, due to bugs in the gethrtime() implementation, there are some cases where the time returned by it can drift (See Solaris bug id 6600939), potentially causing the interval calculation logic to fail. The solution is to retrieve the correct time whenever a drift in the time returned by gethrtime() is detected. That is, do not use the cached time whenever the values (previous and current) returned by gethrtime() are not monotonically increasing. mysys/my_getsystime.c: Do not used the cached time if gethrtime is not monotonic.
231 lines
6.2 KiB
C
231 lines
6.2 KiB
C
/* Copyright (C) 2004 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/* get time since epoc in 100 nanosec units */
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/* thus to get the current time we should use the system function
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with the highest possible resolution */
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/*
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TODO: in functions my_micro_time() and my_micro_time_and_time() there
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exists some common code that should be merged into a function.
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*/
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#include "mysys_priv.h"
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#include "my_static.h"
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#ifdef __NETWARE__
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#include <nks/time.h>
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#endif
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ulonglong my_getsystime()
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{
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#ifdef HAVE_CLOCK_GETTIME
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struct timespec tp;
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clock_gettime(CLOCK_REALTIME, &tp);
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return (ulonglong)tp.tv_sec*10000000+(ulonglong)tp.tv_nsec/100;
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#elif defined(__WIN__)
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LARGE_INTEGER t_cnt;
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if (query_performance_frequency)
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{
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QueryPerformanceCounter(&t_cnt);
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return ((t_cnt.QuadPart / query_performance_frequency * 10000000) +
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((t_cnt.QuadPart % query_performance_frequency) * 10000000 /
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query_performance_frequency) + query_performance_offset);
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}
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return 0;
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#elif defined(__NETWARE__)
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NXTime_t tm;
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NXGetTime(NX_SINCE_1970, NX_NSECONDS, &tm);
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return (ulonglong)tm/100;
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#else
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/* TODO: check for other possibilities for hi-res timestamping */
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struct timeval tv;
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gettimeofday(&tv,NULL);
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return (ulonglong)tv.tv_sec*10000000+(ulonglong)tv.tv_usec*10;
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#endif
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}
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/*
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Return current time
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SYNOPSIS
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my_time()
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flags If MY_WME is set, write error if time call fails
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*/
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time_t my_time(myf flags __attribute__((unused)))
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{
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time_t t;
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#ifdef HAVE_GETHRTIME
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(void) my_micro_time_and_time(&t);
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return t;
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#else
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/* The following loop is here beacuse time() may fail on some systems */
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while ((t= time(0)) == (time_t) -1)
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{
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if (flags & MY_WME)
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fprintf(stderr, "%s: Warning: time() call failed\n", my_progname);
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}
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return t;
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#endif
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}
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/*
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Return time in micro seconds
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SYNOPSIS
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my_micro_time()
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NOTES
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This function is to be used to measure performance in micro seconds.
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As it's not defined whats the start time for the clock, this function
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us only useful to measure time between two moments.
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For windows platforms we need the frequency value of the CUP. This is
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initalized in my_init.c through QueryPerformanceFrequency().
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If Windows platform doesn't support QueryPerformanceFrequency() we will
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obtain the time via GetClockCount, which only supports milliseconds.
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RETURN
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Value in microseconds from some undefined point in time
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*/
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ulonglong my_micro_time()
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{
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#if defined(__WIN__)
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ulonglong newtime;
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GetSystemTimeAsFileTime((FILETIME*)&newtime);
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return (newtime/10);
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#elif defined(HAVE_GETHRTIME)
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return gethrtime()/1000;
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#else
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ulonglong newtime;
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struct timeval t;
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/*
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The following loop is here because gettimeofday may fail on some systems
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*/
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while (gettimeofday(&t, NULL) != 0)
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{}
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newtime= (ulonglong)t.tv_sec * 1000000 + t.tv_usec;
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return newtime;
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#endif /* defined(__WIN__) */
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}
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/*
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Return time in seconds and timer in microseconds (not different start!)
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SYNOPSIS
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my_micro_time_and_time()
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time_arg Will be set to seconds since epoch (00:00:00 UTC,
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January 1, 1970)
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NOTES
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This function is to be useful when we need both the time and microtime.
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For example in MySQL this is used to get the query time start of a query
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and to measure the time of a query (for the slow query log)
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IMPLEMENTATION
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Value of time is as in time() call.
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Value of microtime is same as my_micro_time(), which may be totally
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unrealated to time()
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RETURN
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Value in microseconds from some undefined point in time
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*/
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#define DELTA_FOR_SECONDS LL(500000000) /* Half a second */
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ulonglong my_micro_time_and_time(time_t *time_arg)
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{
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#if defined(__WIN__)
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ulonglong newtime;
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GetSystemTimeAsFileTime((FILETIME*)&newtime);
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*time_arg= (time_t) ((newtime - OFFSET_TO_EPOCH) / 10000000);
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return (newtime/10);
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#elif defined(HAVE_GETHRTIME)
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/*
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Solaris has a very slow time() call. We optimize this by using the very
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fast gethrtime() call and only calling time() every 1/2 second
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*/
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static hrtime_t prev_gethrtime= 0;
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static time_t cur_time= 0;
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hrtime_t cur_gethrtime;
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pthread_mutex_lock(&THR_LOCK_time);
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cur_gethrtime= gethrtime();
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/*
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Due to bugs in the Solaris (x86) implementation of gethrtime(),
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the time returned by it might not be monotonic. Don't use the
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cached time(2) value if this is a case.
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*/
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if ((prev_gethrtime > cur_gethrtime) ||
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((cur_gethrtime - prev_gethrtime) > DELTA_FOR_SECONDS))
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{
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cur_time= time(0);
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prev_gethrtime= cur_gethrtime;
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}
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*time_arg= cur_time;
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pthread_mutex_unlock(&THR_LOCK_time);
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return cur_gethrtime/1000;
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#else
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ulonglong newtime;
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struct timeval t;
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/*
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The following loop is here because gettimeofday may fail on some systems
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*/
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while (gettimeofday(&t, NULL) != 0)
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{}
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*time_arg= t.tv_sec;
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newtime= (ulonglong)t.tv_sec * 1000000 + t.tv_usec;
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return newtime;
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#endif /* defined(__WIN__) */
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}
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/*
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Returns current time
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SYNOPSIS
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my_time_possible_from_micro()
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microtime Value from very recent my_micro_time()
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NOTES
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This function returns the current time. The microtime argument is only used
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if my_micro_time() uses a function that can safely be converted to the
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current time.
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RETURN
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current time
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*/
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time_t my_time_possible_from_micro(ulonglong microtime __attribute__((unused)))
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{
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#if defined(__WIN__)
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time_t t;
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while ((t= time(0)) == (time_t) -1)
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{}
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return t;
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#elif defined(HAVE_GETHRTIME)
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return my_time(0); /* Cached time */
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#else
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return (time_t) (microtime / 1000000);
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#endif /* defined(__WIN__) */
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}
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