Introduce pthread_condattr_setclock()

This is one of the few POSIX APIs that was missing. It lets you choose a
monotonic clock for your condition variables. This might improve perf on
some platforms. It might also grant more flexibility with NTP configs. I
know Qt is one project that believes it needs this. To introduce this, I
needed to change some the *NSYNC APIs, to support passing a clock param.
There's also new benchmarks, demonstrating Cosmopolitan's supremacy over
many libc implementations when it comes to mutex performance. Cygwin has
an alarmingly bad pthread_mutex_t implementation. It is so bad that they
would have been significantly better off if they'd used naive spinlocks.

libc/calls/clock_gettime.c

@@ -24,6 +24,7 @@
 #include "libc/intrin/describeflags.h"
 #include "libc/intrin/strace.h"
 #include "libc/runtime/syslib.internal.h"
+#include "libc/sysv/consts/clock.h"
 
 #ifdef __aarch64__
 #define CGT_VDSO __vdsosym("LINUX_2.6.39", "__kernel_clock_gettime")
@@ -58,14 +59,43 @@ static int __clock_gettime_init(int clockid, struct timespec *ts) {
   return cgt(clockid, ts);
 }
 
+static int clock_gettime_impl(int clock, struct timespec *ts) {
+  int rc;
+  if (!IsLinux())
+    return __clock_gettime(clock, ts);
+TryAgain:
+
+  // Ensure fallback for old Linux sticks.
+  if (clock == 4 /* CLOCK_MONOTONIC_RAW */)
+    clock = CLOCK_MONOTONIC_RAW;
+
+  // Call appropriate implementation.
+  rc = __clock_gettime(clock, ts);
+
+  // CLOCK_MONOTONIC_RAW is Linux 2.6.28+ so not available on RHEL5
+  if (rc == -EINVAL && clock == 4 /* CLOCK_MONOTONIC_RAW */) {
+    CLOCK_MONOTONIC_RAW = CLOCK_MONOTONIC;
+    CLOCK_MONOTONIC_RAW_APPROX = CLOCK_MONOTONIC;
+    goto TryAgain;
+  }
+
+  return rc;
+}
+
 /**
  * Returns nanosecond time.
  *
  * @param clock supports the following values across OSes:
  *    - `CLOCK_REALTIME`
  *    - `CLOCK_MONOTONIC`
+ *    - `CLOCK_MONOTONIC_RAW`
+ *    - `CLOCK_MONOTONIC_RAW_APPROX`
+ *    - `CLOCK_REALTIME_FAST`
  *    - `CLOCK_REALTIME_COARSE`
+ *    - `CLOCK_REALTIME_PRECISE`
+ *    - `CLOCK_MONOTONIC_FAST`
  *    - `CLOCK_MONOTONIC_COARSE`
+ *    - `CLOCK_MONOTONIC_PRECISE`
  *    - `CLOCK_THREAD_CPUTIME_ID`
  *    - `CLOCK_PROCESS_CPUTIME_ID`
  * @param ts is where the result is stored (or null to do clock check)
@@ -80,7 +110,7 @@ static int __clock_gettime_init(int clockid, struct timespec *ts) {
  */
 int clock_gettime(int clock, struct timespec *ts) {
   // threads on win32 stacks call this so we can't asan check *ts
-  int rc = __clock_gettime(clock, ts);
+  int rc = clock_gettime_impl(clock, ts);
   if (rc) {
     errno = -rc;
     rc = -1;

libc/calls/clock_nanosleep.c

@@ -19,6 +19,7 @@
 #include "libc/calls/struct/timespec.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
+#include "libc/sysv/consts/clock.h"
 #include "libc/sysv/consts/timer.h"
 
 /**
@@ -79,18 +80,32 @@
 errno_t clock_nanosleep(int clock, int flags,        //
                         const struct timespec *req,  //
                         struct timespec *rem) {
-  if (IsMetal()) {
+  if (IsMetal())
     return ENOSYS;
-  }
   if (clock == 127 ||              //
       (flags & ~TIMER_ABSTIME) ||  //
       req->tv_sec < 0 ||           //
-      !(0 <= req->tv_nsec && req->tv_nsec <= 999999999)) {
+      !(0 <= req->tv_nsec && req->tv_nsec <= 999999999))
     return EINVAL;
+  int rc;
+  errno_t err, old = errno;
+
+TryAgain:
+  // Ensure fallback for old Linux sticks.
+  if (IsLinux() && clock == 4 /* CLOCK_MONOTONIC_RAW */)
+    clock = CLOCK_MONOTONIC_RAW;
+
+  rc = sys_clock_nanosleep(clock, flags, req, rem);
+
+  // CLOCK_MONOTONIC_RAW is Linux 2.6.28+ so not available on RHEL5
+  if (IsLinux() && rc && errno == EINVAL &&
+      clock == 4 /* CLOCK_MONOTONIC_RAW */) {
+    CLOCK_MONOTONIC_RAW = CLOCK_MONOTONIC;
+    CLOCK_MONOTONIC_RAW_APPROX = CLOCK_MONOTONIC;
+    goto TryAgain;
   }
-  errno_t old = errno;
-  int rc = sys_clock_nanosleep(clock, flags, req, rem);
-  errno_t err = !rc ? 0 : errno;
+
+  err = !rc ? 0 : errno;
   errno = old;
   return err;
 }