github.com/afumu/libc@v0.0.6/musl/src/stdio/ftrylockfile.c (about)

     1  #include "stdio_impl.h"
     2  #include "pthread_impl.h"
     3  #include <limits.h>
     4  
     5  void __do_orphaned_stdio_locks()
     6  {
     7  	FILE *f;
     8  	for (f=__pthread_self()->stdio_locks; f; f=f->next_locked)
     9  		a_store(&f->lock, 0x40000000);
    10  }
    11  
    12  void __unlist_locked_file(FILE *f)
    13  {
    14  	if (f->lockcount) {
    15  		if (f->next_locked) f->next_locked->prev_locked = f->prev_locked;
    16  		if (f->prev_locked) f->prev_locked->next_locked = f->next_locked;
    17  		else __pthread_self()->stdio_locks = f->next_locked;
    18  	}
    19  }
    20  
    21  void __register_locked_file(FILE *f, pthread_t self)
    22  {
    23  	f->lockcount = 1;
    24  	f->prev_locked = 0;
    25  	f->next_locked = self->stdio_locks;
    26  	if (f->next_locked) f->next_locked->prev_locked = f;
    27  	self->stdio_locks = f;
    28  }
    29  
    30  int ftrylockfile(FILE *f)
    31  {
    32  	pthread_t self = __pthread_self();
    33  	int tid = self->tid;
    34  	int owner = f->lock;
    35  	if ((owner & ~MAYBE_WAITERS) == tid) {
    36  		if (f->lockcount == LONG_MAX)
    37  			return -1;
    38  		f->lockcount++;
    39  		return 0;
    40  	}
    41  	if (owner < 0) f->lock = owner = 0;
    42  	if (owner || a_cas(&f->lock, 0, tid))
    43  		return -1;
    44  	__register_locked_file(f, self);
    45  	return 0;
    46  }