libc-top-half/musl/src/thread/pthread_mutex_timedlock.c

   1 #include "pthread_impl.h"
   2
   3 #ifdef __wasilibc_unmodified_upstream
   4 #define IS32BIT(x) !((x)+0x80000000ULL>>32)
   5 #define CLAMP(x) (int)(IS32BIT(x) ? (x) : 0x7fffffffU+((0ULL+(x))>>63))
   6
   7 static int __futex4(volatile void *addr, int op, int val, const struct timespec *to)
   8 {
   9 #ifdef SYS_futex_time64
  10         time_t s = to ? to->tv_sec : 0;
  11         long ns = to ? to->tv_nsec : 0;
  12         int r = -ENOSYS;
  13         if (SYS_futex == SYS_futex_time64 || !IS32BIT(s))
  14                 r = __syscall(SYS_futex_time64, addr, op, val,
  15                         to ? ((long long[]){s, ns}) : 0);
  16         if (SYS_futex == SYS_futex_time64 || r!=-ENOSYS) return r;
  17         to = to ? (void *)(long[]){CLAMP(s), ns} : 0;
  18 #endif
  19         return __syscall(SYS_futex, addr, op, val, to);
  20 }
  21
  22 static int pthread_mutex_timedlock_pi(pthread_mutex_t *restrict m, const struct timespec *restrict at)
  23 {
  24         int type = m->_m_type;
  25         int priv = (type & 128) ^ 128;
  26         pthread_t self = __pthread_self();
  27         int e;
  28
  29         if (!priv) self->robust_list.pending = &m->_m_next;
  30
  31         do e = -__futex4(&m->_m_lock, FUTEX_LOCK_PI|priv, 0, at);
  32         while (e==EINTR);
  33         if (e) self->robust_list.pending = 0;
  34
  35         switch (e) {
  36         case 0:
  37                 /* Catch spurious success for non-robust mutexes. */
  38                 if (!(type&4) && ((m->_m_lock & 0x40000000) || m->_m_waiters)) {
  39                         a_store(&m->_m_waiters, -1);
  40                         __syscall(SYS_futex, &m->_m_lock, FUTEX_UNLOCK_PI|priv);
  41                         self->robust_list.pending = 0;
  42                         break;
  43                 }
  44                 /* Signal to trylock that we already have the lock. */
  45                 m->_m_count = -1;
  46                 return __pthread_mutex_trylock(m);
  47         case ETIMEDOUT:
  48                 return e;
  49         case EDEADLK:
  50                 if ((type&3) == PTHREAD_MUTEX_ERRORCHECK) return e;
  51         }
  52         do e = __timedwait(&(int){0}, 0, CLOCK_REALTIME, at, 1);
  53         while (e != ETIMEDOUT);
  54         return e;
  55 }
  56 #endif
  57
  58 int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec *restrict at)
  59 {
  60         if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL
  61             && !a_cas(&m->_m_lock, 0, EBUSY))
  62                 return 0;
  63
  64         int type = m->_m_type;
  65         int r, t, priv = (type & 128) ^ 128;
  66
  67         r = __pthread_mutex_trylock(m);
  68         if (r != EBUSY) return r;
  69
  70 #ifdef __wasilibc_unmodified_upstream
  71         if (type&8) return pthread_mutex_timedlock_pi(m, at);
  72 #endif
  73
  74         int spins = 100;
  75         while (spins-- && m->_m_lock && !m->_m_waiters) a_spin();
  76
  77         while ((r=__pthread_mutex_trylock(m)) == EBUSY) {
  78                 r = m->_m_lock;
  79                 int own = r & 0x3fffffff;
  80                 if (!own && (!r || (type&4)))
  81                         continue;
  82                 if ((type&3) == PTHREAD_MUTEX_ERRORCHECK
  83                     && own == __pthread_self()->tid)
  84                         return EDEADLK;
  85
  86                 a_inc(&m->_m_waiters);
  87                 t = r | 0x80000000;
  88                 a_cas(&m->_m_lock, r, t);
  89                 r = __timedwait(&m->_m_lock, t, CLOCK_REALTIME, at, priv);
  90                 a_dec(&m->_m_waiters);
  91                 if (r && r != EINTR) break;
  92         }
  93         return r;
  94 }
  95
  96 weak_alias(__pthread_mutex_timedlock, pthread_mutex_timedlock);