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libs/libc/time/localtime: fix race condition

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fix race condition on create the instance of lcl/gmt

Signed-off-by: chao.an <anchao@xiaomi.com>
This commit is contained in:
chao.an 2021-02-02 17:26:41 +08:00 committed by Xiang Xiao
parent 837e1a72a4
commit 6a6ad96066
1 changed files with 38 additions and 10 deletions
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48
libs/libc/time/lib_localtime.c
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@ -321,6 +321,8 @@ static const char g_wildabbr[] = WILDABBR;
static char g_lcl_tzname[MY_TZNAME_MAX + 1];
static int g_lcl_isset;
static int g_gmt_isset;
static sem_t g_lcl_sem = SEM_INITIALIZER(1);
static sem_t g_gmt_sem = SEM_INITIALIZER(1);
/* Section 4.12.3 of X3.159-1989 requires that
* Except for the strftime function, these functions [asctime,
@ -414,6 +416,28 @@ static FAR struct state_s *gmtptr;
* Private Functions
****************************************************************************/
static void tz_semtake(FAR sem_t *sem)
{
int errcode = 0;
int ret;
do
{
ret = _SEM_WAIT(sem);
if (ret < 0)
{
errcode = _SEM_ERRNO(ret);
DEBUGASSERT(errcode == EINTR || errcode == ECANCELED);
}
}
while (ret < 0 && errcode == EINTR);
}
static void tz_semgive(FAR sem_t *sem)
{
DEBUGVERIFY(_SEM_POST(sem));
}
static int_fast32_t detzcode(FAR const char *const codep)
{
int_fast32_t result;
@ -1639,29 +1663,29 @@ static void gmtload(FAR struct state_s *const sp)
static void tzsetwall(void)
{
tz_semtake(&g_lcl_sem);
if (g_lcl_isset < 0)
{
tz_semgive(&g_lcl_sem);
return;
}
g_lcl_isset = -1;
if (lclptr == NULL)
{
lclptr = lib_malloc(sizeof *lclptr);
if (lclptr == NULL)
{
settzname(); /* all we can do */
return;
}
}
if (tzload(NULL, lclptr, TRUE) != 0)
if (lclptr != NULL && tzload(NULL, lclptr, TRUE) != 0)
{
gmtload(lclptr);
}
settzname();
g_lcl_isset = -1;
tz_semgive(&g_lcl_sem);
}
/* The easy way to behave "as if no library function calls" localtime
@ -1791,16 +1815,20 @@ static struct tm *localsub(FAR const time_t * const timep,
static struct tm *gmtsub(FAR const time_t * const timep,
const int_fast32_t offset, struct tm *const tmp)
{
tz_semtake(&g_gmt_sem);
if (!g_gmt_isset)
{
gmtptr = lib_malloc(sizeof *gmtptr);
g_gmt_isset = gmtptr != NULL;
if (g_gmt_isset)
if (gmtptr != NULL)
{
gmtload(gmtptr);
g_gmt_isset = 1;
}
}
tz_semgive(&g_gmt_sem);
return timesub(timep, offset, gmtptr, tmp);
}