github.com/afumu/libc@v0.0.6/musl/src/stdio/getc.h (about)

     1  #include "stdio_impl.h"
     2  #include "pthread_impl.h"
     3  
     4  #ifdef __GNUC__
     5  __attribute__((__noinline__))
     6  #endif
     7  static int locking_getc(FILE *f)
     8  {
     9  	if (a_cas(&f->lock, 0, MAYBE_WAITERS-1)) __lockfile(f);
    10  	int c = getc_unlocked(f);
    11  	if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
    12  		__wake(&f->lock, 1, 1);
    13  	return c;
    14  }
    15  
    16  static inline int do_getc(FILE *f)
    17  {
    18  	int l = f->lock;
    19  	if (l < 0 || l && (l & ~MAYBE_WAITERS) == __pthread_self()->tid)
    20  		return getc_unlocked(f);
    21  	return locking_getc(f);
    22  }