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

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