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Normally, we are often reading local time rather than setting time zone,

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replace mutex with rwlock, this should eliminate lock contention in
most cases.
This commit is contained in:
David Xu 2008-04-01 06:56:11 +00:00
parent 18967c1918
commit ad4a96ba13
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=177824
1 changed files with 63 additions and 22 deletions
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85
lib/libc/stdtime/localtime.c
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@ -34,6 +34,21 @@ __FBSDID("$FreeBSD$");
#define _MUTEX_LOCK(x) if (__isthreaded) _pthread_mutex_lock(x)
#define _MUTEX_UNLOCK(x) if (__isthreaded) _pthread_mutex_unlock(x)
#define _RWLOCK_RDLOCK(x) \
do { \
if (__isthreaded) _pthread_rwlock_rdlock(x); \
} while (0)
#define _RWLOCK_WRLOCK(x) \
do { \
if (__isthreaded) _pthread_rwlock_wrlock(x); \
} while (0)
#define _RWLOCK_UNLOCK(x) \
do { \
if (__isthreaded) _pthread_rwlock_unlock(x); \
} while (0)
/*
** SunOS 4.1.1 headers lack O_BINARY.
*/
@ -196,7 +211,7 @@ static struct state gmtmem;
static char lcl_TZname[TZ_STRLEN_MAX + 1];
static int lcl_is_set;
static int gmt_is_set;
static pthread_mutex_t lcl_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_rwlock_t lcl_rwlock = PTHREAD_RWLOCK_INITIALIZER;
static pthread_mutex_t gmt_mutex = PTHREAD_MUTEX_INITIALIZER;
char * tzname[2] = {
@ -949,10 +964,18 @@ struct state * const sp;
}
static void
tzsetwall_basic(void)
tzsetwall_basic(int rdlocked)
{
if (lcl_is_set < 0)
if (!rdlocked)
_RWLOCK_RDLOCK(&lcl_rwlock);
if (lcl_is_set < 0) {
if (!rdlocked)
_RWLOCK_UNLOCK(&lcl_rwlock);
return;
}
_RWLOCK_UNLOCK(&lcl_rwlock);
_RWLOCK_WRLOCK(&lcl_rwlock);
lcl_is_set = -1;
#ifdef ALL_STATE
@ -960,6 +983,9 @@ tzsetwall_basic(void)
lclptr = (struct state *) malloc(sizeof *lclptr);
if (lclptr == NULL) {
settzname(); /* all we can do */
_RWLOCK_UNLOCK(&lcl_rwlock);
if (rdlocked)
_RWLOCK_RDLOCK(&lcl_rwlock);
return;
}
}
@ -967,29 +993,39 @@ tzsetwall_basic(void)
if (tzload((char *) NULL, lclptr) != 0)
gmtload(lclptr);
settzname();
_RWLOCK_UNLOCK(&lcl_rwlock);
if (rdlocked)
_RWLOCK_RDLOCK(&lcl_rwlock);
}
void
tzsetwall(void)
{
_MUTEX_LOCK(&lcl_mutex);
tzsetwall_basic();
_MUTEX_UNLOCK(&lcl_mutex);
tzsetwall_basic(0);
}
static void
tzset_basic(void)
tzset_basic(int rdlocked)
{
const char * name;
name = getenv("TZ");
if (name == NULL) {
tzsetwall_basic();
tzsetwall_basic(rdlocked);
return;
}
if (lcl_is_set > 0 && strcmp(lcl_TZname, name) == 0)
if (!rdlocked)
_RWLOCK_RDLOCK(&lcl_rwlock);
if (lcl_is_set > 0 && strcmp(lcl_TZname, name) == 0) {
if (!rdlocked)
_RWLOCK_UNLOCK(&lcl_rwlock);
return;
}
_RWLOCK_UNLOCK(&lcl_rwlock);
_RWLOCK_WRLOCK(&lcl_rwlock);
lcl_is_set = strlen(name) < sizeof lcl_TZname;
if (lcl_is_set)
(void) strcpy(lcl_TZname, name);
@ -999,6 +1035,9 @@ tzset_basic(void)
lclptr = (struct state *) malloc(sizeof *lclptr);
if (lclptr == NULL) {
settzname(); /* all we can do */
_RWLOCK_UNLOCK(&lcl_rwlock);
if (rdlocked)
_RWLOCK_RDLOCK(&lcl_rwlock);
return;
}
}
@ -1018,14 +1057,16 @@ tzset_basic(void)
if (name[0] == ':' || tzparse(name, lclptr, FALSE) != 0)
(void) gmtload(lclptr);
settzname();
_RWLOCK_UNLOCK(&lcl_rwlock);
if (rdlocked)
_RWLOCK_RDLOCK(&lcl_rwlock);
}
void
tzset(void)
{
_MUTEX_LOCK(&lcl_mutex);
tzset_basic();
_MUTEX_UNLOCK(&lcl_mutex);
tzset_basic(0);
}
/*
@ -1110,13 +1151,13 @@ const time_t * const timep;
return(NULL);
_pthread_setspecific(localtime_key, p_tm);
}
_pthread_mutex_lock(&lcl_mutex);
tzset_basic();
_RWLOCK_RDLOCK(&lcl_rwlock);
tzset_basic(1);
localsub(timep, 0L, p_tm);
_pthread_mutex_unlock(&lcl_mutex);
_RWLOCK_UNLOCK(&lcl_rwlock);
return(p_tm);
} else {
tzset_basic();
tzset_basic(0);
localsub(timep, 0L, &tm);
return(&tm);
}
@ -1131,10 +1172,10 @@ localtime_r(timep, tm)
const time_t * const timep;
struct tm * tm;
{
_MUTEX_LOCK(&lcl_mutex);
tzset_basic();
_RWLOCK_RDLOCK(&lcl_rwlock);
tzset_basic(1);
localsub(timep, 0L, tm);
_MUTEX_UNLOCK(&lcl_mutex);
_RWLOCK_UNLOCK(&lcl_rwlock);
return tm;
}
@ -1686,10 +1727,10 @@ mktime(tmp)
struct tm * const tmp;
{
time_t mktime_return_value;
_MUTEX_LOCK(&lcl_mutex);
tzset_basic();
_RWLOCK_RDLOCK(&lcl_rwlock);
tzset_basic(1);
mktime_return_value = time1(tmp, localsub, 0L);
_MUTEX_UNLOCK(&lcl_mutex);
_RWLOCK_UNLOCK(&lcl_rwlock);
return(mktime_return_value);
}