Use *NSYNC for POSIX threads locking APIs

Condition variables, barriers, and r/w locks now work very well.

third_party/nsync/debug.h

@@ -0,0 +1,39 @@
+#ifndef NSYNC_DEBUG_H_
+#define NSYNC_DEBUG_H_
+#include "third_party/nsync/cv.h"
+#include "third_party/nsync/mu.h"
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+/* Debugging operations for mutexes and condition variables.
+
+   These operations should not be relied upon for normal functionality.
+   The implementation may be slow, output formats may change, and the
+   implementation is free to yield the empty string. */
+
+/* Place in buf[0,..,n-1] a nul-terminated, human readable string
+   indicative of some of the internal state of the mutex or condition
+   variable, and return buf. If n>=4, buffer overflow is indicated by
+   placing the characters "..." at the end of the string.
+
+   The *_and_waiters() variants attempt to output the waiter lists in
+   addition to the basic state. These variants may acquire internal
+   locks and follow internal pointers. Thus, they are riskier if invoked
+   in an address space whose overall health is uncertain. */
+char *nsync_mu_debug_state(nsync_mu *mu, char *buf, int n);
+char *nsync_cv_debug_state(nsync_cv *cv, char *buf, int n);
+char *nsync_mu_debug_state_and_waiters(nsync_mu *mu, char *buf, int n);
+char *nsync_cv_debug_state_and_waiters(nsync_cv *cv, char *buf, int n);
+
+/* Like nsync_*_debug_state_and_waiters(), but ignoring all locking and
+   safety considerations, and using an internal, possibly static buffer
+   that may be overwritten by subsequent or concurrent calls to these
+   routines. These variants should be used only from an interactive
+   debugger, when all other threads are stopped; the debugger is
+   expected to recover from errors. */
+char *nsync_mu_debugger(nsync_mu *mu);
+char *nsync_cv_debugger(nsync_cv *cv);
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* NSYNC_DEBUG_H_ */