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Added basic spinlock implementation using builtins.

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This will be used on platforms without pthread_spin_lock(), e.g. Android targeting API level < 24.

Implementation lifted from spinlock.h in libobjc2.
This commit is contained in:
Frederik Seiffert 2019-05-07 17:38:54 +02:00
parent 8ed7ccea9e
commit 3a97bb08f4
1 changed files with 22 additions and 3 deletions
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25
Source/NSThread.m
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@ -38,21 +38,40 @@
// Dummy implementatation
// cleaner than IFDEF'ing the code everywhere
#if !(HAVE_PTHREAD_SPIN_LOCK)
#warning no spin_locks, using dummy versions
typedef int pthread_spinlock_t;
typedef volatile int pthread_spinlock_t;
int pthread_spin_init(pthread_spinlock_t *lock, int pshared)
{
#if DEBUG
#if DEBUG && !__has_builtin(__sync_bool_compare_and_swap)
fprintf(stderr,"NSThread.m: Warning this platform does not support spin locks - init.\n");
#endif
return 0;
}
int pthread_spin_lock(pthread_spinlock_t *lock)
{
#if __has_builtin(__sync_bool_compare_and_swap)
int count = 0;
// Set the spin lock value to 1 if it is 0.
while(!__sync_bool_compare_and_swap(lock, 0, 1))
{
count++;
if (0 == count % 10)
{
// If it is already 1, let another thread play with the CPU for a
// bit then try again.
sleep(0);
}
}
#else
#warning no spin_locks, using dummy versions
#endif
return 0;
}
int pthread_spin_unlock(pthread_spinlock_t *lock)
{
#if __has_builtin(__sync_bool_compare_and_swap)
__sync_synchronize();
*lock = 0;
#endif
return 0;
}
int pthread_spin_destroy(pthread_spinlock_t *lock)