simplify unified timed wait code, drop support for newer method

the new absolute-time-based wait kernelside was hard to get right and
basically just code duplication. it could only improve "performance"
when waiting, and even then, the improvement was just slight drop in
cpu usage during a wait.

actually, with vdso clock_gettime, the "old" way will be even faster
than the "new" way if the time has already expired, since it will not
invoke any syscalls. it can determine entirely in userspace that it
needs to return ETIMEDOUT.

src/thread/__timedwait.c

@@ -4,45 +4,42 @@
 #include "futex.h"
 #include "syscall.h"
 
-static int do_wait(volatile int *addr, int val, clockid_t clk, const struct timespec *at, int cp, int priv)
+static int do_wait(volatile int *addr, int val,
+	clockid_t clk, const struct timespec *at, int priv)
 {
-	int r, flag = 0;
+	int r;
 	struct timespec to, *top=0;
 
-	if (!at) goto notimeout;
-	if (at->tv_nsec >= 1000000000UL)
-		return EINVAL;
-	if (clk == CLOCK_REALTIME || clk == CLOCK_MONOTONIC) {
-		if (clk == CLOCK_REALTIME) flag = FUTEX_CLOCK_REALTIME;
-		if (cp) r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT_BITSET|flag, val, at, 0, -1);
-		else r = -__syscall(SYS_futex, addr, FUTEX_WAIT_BITSET|flag, val, at, 0, -1);
-		if (r != EINVAL && r != ENOSYS) goto done;
-	}
-	if (clock_gettime(clk, &to)) return EINVAL;
-	to.tv_sec = at->tv_sec - to.tv_sec;
-	if ((to.tv_nsec = at->tv_nsec - to.tv_nsec) < 0) {
-		to.tv_sec--;
-		to.tv_nsec += 1000000000;
+	if (at) {
+		if (at->tv_nsec >= 1000000000UL) return EINVAL;
+		if (clock_gettime(clk, &to)) return EINVAL;
+		to.tv_sec = at->tv_sec - to.tv_sec;
+		if ((to.tv_nsec = at->tv_nsec - to.tv_nsec) < 0) {
+			to.tv_sec--;
+			to.tv_nsec += 1000000000;
+		}
+		if (to.tv_sec < 0) return ETIMEDOUT;
+		top = &to;
 	}
-	if (to.tv_sec < 0) return ETIMEDOUT;
-	top = &to;
-notimeout:
-	if (cp) r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT, val, top);
-	else r = -__syscall(SYS_futex, addr, FUTEX_WAIT, val, top);
-done:
+
+	r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT, val, top);
 	if (r == EINTR || r == EINVAL || r == ETIMEDOUT) return r;
 	return 0;
 }
 
-int __timedwait(volatile int *addr, int val, clockid_t clk, const struct timespec *at, void (*cleanup)(void *), void *arg, int priv)
+int __timedwait(volatile int *addr, int val,
+	clockid_t clk, const struct timespec *at,
+	void (*cleanup)(void *), void *arg, int priv)
 {
-	int r;
-	if (cleanup) {
-		pthread_cleanup_push(cleanup, arg);
-		r = do_wait(addr, val, clk, at, 1, priv);
-		pthread_cleanup_pop(0);
-	} else {
-		r = do_wait(addr, val, clk, at, 0, priv);
-	}
+	int r, cs;
+
+	if (!cleanup) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+	pthread_cleanup_push(cleanup, arg);
+
+	r = do_wait(addr, val, clk, at, priv);
+
+	pthread_cleanup_pop(0);
+	if (!cleanup) pthread_setcancelstate(cs, 0);
+
 	return r;
 }