select: switch select() and poll() over to hrtimers

With lots of help, input and cleanups from Thomas Gleixner

This patch switches select() and poll() over to hrtimers.

The core of the patch is replacing the "s64 timeout" with a
"struct timespec end_time" in all the plumbing.

But most of the diffstat comes from using the just introduced helpers:
	poll_select_set_timeout
	poll_select_copy_remaining
	timespec_add_safe
which make manipulating the timespec easier and less error-prone.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

fs/compat.c

@@ -1568,7 +1568,8 @@ int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
 	((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 
 int compat_core_sys_select(int n, compat_ulong_t __user *inp,
-	compat_ulong_t __user *outp, compat_ulong_t __user *exp, s64 *timeout)
+	compat_ulong_t __user *outp, compat_ulong_t __user *exp,
+	struct timespec *end_time)
 {
 	fd_set_bits fds;
 	void *bits;
@@ -1615,7 +1616,7 @@ int compat_core_sys_select(int n, compat_ulong_t __user *inp,
 	zero_fd_set(n, fds.res_out);
 	zero_fd_set(n, fds.res_ex);
 
-	ret = do_select(n, &fds, timeout);
+	ret = do_select(n, &fds, end_time);
 
 	if (ret < 0)
 		goto out;
@@ -1641,7 +1642,7 @@ asmlinkage long compat_sys_select(int n, compat_ulong_t __user *inp,
 	compat_ulong_t __user *outp, compat_ulong_t __user *exp,
 	struct compat_timeval __user *tvp)
 {
-	s64 timeout = -1;
+	struct timespec end_time, *to = NULL;
 	struct compat_timeval tv;
 	int ret;
 
@@ -1649,43 +1650,14 @@ asmlinkage long compat_sys_select(int n, compat_ulong_t __user *inp,
 		if (copy_from_user(&tv, tvp, sizeof(tv)))
 			return -EFAULT;
 
-		if (tv.tv_sec < 0 || tv.tv_usec < 0)
+		to = &end_time;
+		if (poll_select_set_timeout(to, tv.tv_sec,
+					    tv.tv_usec * NSEC_PER_USEC))
 			return -EINVAL;
-
-		/* Cast to u64 to make GCC stop complaining */
-		if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS)
-			timeout = -1;	/* infinite */
-		else {
-			timeout = DIV_ROUND_UP(tv.tv_usec, 1000000/HZ);
-			timeout += tv.tv_sec * HZ;
-		}
 	}
 
-	ret = compat_core_sys_select(n, inp, outp, exp, &timeout);
-
-	if (tvp) {
-		struct compat_timeval rtv;
-
-		if (current->personality & STICKY_TIMEOUTS)
-			goto sticky;
-		rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));
-		rtv.tv_sec = timeout;
-		if (compat_timeval_compare(&rtv, &tv) >= 0)
-			rtv = tv;
-		if (copy_to_user(tvp, &rtv, sizeof(rtv))) {
-sticky:
-			/*
-			 * If an application puts its timeval in read-only
-			 * memory, we don't want the Linux-specific update to
-			 * the timeval to cause a fault after the select has
-			 * completed successfully. However, because we're not
-			 * updating the timeval, we can't restart the system
-			 * call.
-			 */
-			if (ret == -ERESTARTNOHAND)
-				ret = -EINTR;
-		}
-	}
+	ret = compat_core_sys_select(n, inp, outp, exp, to);
+	ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 
 	return ret;
 }
@@ -1698,15 +1670,16 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp,
 {
 	compat_sigset_t ss32;
 	sigset_t ksigmask, sigsaved;
-	s64 timeout = MAX_SCHEDULE_TIMEOUT;
 	struct compat_timespec ts;
+	struct timespec end_time, *to = NULL;
 	int ret;
 
 	if (tsp) {
 		if (copy_from_user(&ts, tsp, sizeof(ts)))
 			return -EFAULT;
 
-		if (ts.tv_sec < 0 || ts.tv_nsec < 0)
+		to = &end_time;
+		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 			return -EINVAL;
 	}
 
@@ -1721,51 +1694,8 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp,
 		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 	}
 
-	do {
-		if (tsp) {
-			if ((unsigned long)ts.tv_sec < MAX_SELECT_SECONDS) {
-				timeout = DIV_ROUND_UP(ts.tv_nsec, 1000000000/HZ);
-				timeout += ts.tv_sec * (unsigned long)HZ;
-				ts.tv_sec = 0;
-				ts.tv_nsec = 0;
-			} else {
-				ts.tv_sec -= MAX_SELECT_SECONDS;
-				timeout = MAX_SELECT_SECONDS * HZ;
-			}
-		}
-
-		ret = compat_core_sys_select(n, inp, outp, exp, &timeout);
-
-	} while (!ret && !timeout && tsp && (ts.tv_sec || ts.tv_nsec));
-
-	if (tsp) {
-		struct compat_timespec rts;
-
-		if (current->personality & STICKY_TIMEOUTS)
-			goto sticky;
-
-		rts.tv_sec = timeout / HZ;
-		rts.tv_nsec = (timeout % HZ) * (NSEC_PER_SEC/HZ);
-		if (rts.tv_nsec >= NSEC_PER_SEC) {
-			rts.tv_sec++;
-			rts.tv_nsec -= NSEC_PER_SEC;
-		}
-		if (compat_timespec_compare(&rts, &ts) >= 0)
-			rts = ts;
-		if (copy_to_user(tsp, &rts, sizeof(rts))) {
-sticky:
-			/*
-			 * If an application puts its timeval in read-only
-			 * memory, we don't want the Linux-specific update to
-			 * the timeval to cause a fault after the select has
-			 * completed successfully. However, because we're not
-			 * updating the timeval, we can't restart the system
-			 * call.
-			 */
-			if (ret == -ERESTARTNOHAND)
-				ret = -EINTR;
-		}
-	}
+	ret = compat_core_sys_select(n, inp, outp, exp, to);
+	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 
 	if (ret == -ERESTARTNOHAND) {
 		/*
@@ -1810,18 +1740,16 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
 	compat_sigset_t ss32;
 	sigset_t ksigmask, sigsaved;
 	struct compat_timespec ts;
-	s64 timeout = -1;
+	struct timespec end_time, *to = NULL;
 	int ret;
 
 	if (tsp) {
 		if (copy_from_user(&ts, tsp, sizeof(ts)))
 			return -EFAULT;
 
-		/* We assume that ts.tv_sec is always lower than
-		   the number of seconds that can be expressed in
-		   an s64. Otherwise the compiler bitches at us */
-		timeout = DIV_ROUND_UP(ts.tv_nsec, 1000000000/HZ);
-		timeout += ts.tv_sec * HZ;
+		to = &end_time;
+		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
+			return -EINVAL;
 	}
 
 	if (sigmask) {
@@ -1835,7 +1763,7 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
 		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 	}
 
-	ret = do_sys_poll(ufds, nfds, &timeout);
+	ret = do_sys_poll(ufds, nfds, to);
 
 	/* We can restart this syscall, usually */
 	if (ret == -EINTR) {
@@ -1853,31 +1781,7 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
 	} else if (sigmask)
 		sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 
-	if (tsp && timeout >= 0) {
-		struct compat_timespec rts;
-
-		if (current->personality & STICKY_TIMEOUTS)
-			goto sticky;
-		/* Yes, we know it's actually an s64, but it's also positive. */
-		rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
-					1000;
-		rts.tv_sec = timeout;
-		if (compat_timespec_compare(&rts, &ts) >= 0)
-			rts = ts;
-		if (copy_to_user(tsp, &rts, sizeof(rts))) {
-sticky:
-			/*
-			 * If an application puts its timeval in read-only
-			 * memory, we don't want the Linux-specific update to
-			 * the timeval to cause a fault after the select has
-			 * completed successfully. However, because we're not
-			 * updating the timeval, we can't restart the system
-			 * call.
-			 */
-			if (ret == -ERESTARTNOHAND && timeout >= 0)
-				ret = -EINTR;
-		}
-	}
+	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 
 	return ret;
 }

include/linux/poll.h

@@ -114,11 +114,11 @@ void zero_fd_set(unsigned long nr, unsigned long *fdset)
 
 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 
-extern int do_select(int n, fd_set_bits *fds, s64 *timeout);
+extern int do_select(int n, fd_set_bits *fds, struct timespec *end_time);
 extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds,
-		       s64 *timeout);
+		       struct timespec *end_time);
 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
-			   fd_set __user *exp, s64 *timeout);
+			   fd_set __user *exp, struct timespec *end_time);
 
 extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);