29 lines
830 B
C
29 lines
830 B
C
#include "stdio_impl.h"
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#include "pthread_impl.h"
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int __lockfile(FILE *f)
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{
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int owner, tid = __pthread_self()->tid;
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if (f->lock == tid)
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return 0;
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while ((owner = a_cas(&f->lock, 0, tid)))
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__wait(&f->lock, &f->waiters, owner, 1);
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return 1;
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}
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void __unlockfile(FILE *f)
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{
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a_store(&f->lock, 0);
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/* The following read is technically invalid under situations
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* of self-synchronized destruction. Another thread may have
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* called fclose as soon as the above store has completed.
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* Nonetheless, since FILE objects always live in memory
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* obtained by malloc from the heap, it's safe to assume
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* the dereferences below will not fault. In the worst case,
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* a spurious syscall will be made. If the implementation of
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* malloc changes, this assumption needs revisiting. */
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if (f->waiters) __wake(&f->lock, 1, 1);
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}
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