newlib/libc/time/tzlock.c

   1 /*
   2 FUNCTION
   3 <<__tz_lock>>, <<__tz_unlock>>---lock time zone global variables
   4
   5 INDEX
   6         __tz_lock
   7 INDEX
   8         __tz_unlock
   9
  10 SYNOPSIS
  11         #include "local.h"
  12         void __tz_lock (void);
  13         void __tz_unlock (void);
  14
  15 DESCRIPTION
  16 The <<tzset>> facility functions call these functions when they need to
  17 ensure the values of global variables.  The version of these routines
  18 supplied in the library use the lock API defined in sys/lock.h.  If multiple
  19 threads of execution can call the time functions and give up scheduling in
  20 the middle, then you you need to define your own versions of these functions
  21 in order to safely lock the time zone variables during a call.  If you do
  22 not, the results of <<localtime>>, <<mktime>>, <<ctime>>, and <<strftime>>
  23 are undefined.
  24
  25 The lock <<__tz_lock>> may not be called recursively; that is,
  26 a call <<__tz_lock>> will always lock all subsequent <<__tz_lock>> calls
  27 until the corresponding <<__tz_unlock>> call on the same thread is made.
  28 */
  29
  30 #include <_ansi.h>
  31 #include "local.h"
  32 #include <sys/lock.h>
  33
  34 #ifndef __SINGLE_THREAD__
  35 __LOCK_INIT(static, __tz_mutex);
  36 #endif
  37
  38 void
  39 __tz_lock (void)
  40 {
  41 #ifndef __SINGLE_THREAD__
  42   __lock_acquire(__tz_mutex);
  43 #endif
  44 }
  45
  46 void
  47 __tz_unlock (void)
  48 {
  49 #ifndef __SINGLE_THREAD__
  50   __lock_release(__tz_mutex);
  51 #endif
  52 }