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>

1 files changed, 88 insertions, 175 deletions

diff --git a/fs/select.c b/fs/select.c
index 1180a62..f6dceb5 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -24,6 +24,7 @@
 #include <linux/fdtable.h>
 #include <linux/fs.h>
 #include <linux/rcupdate.h>
+#include <linux/hrtimer.h>
 
 #include <asm/uaccess.h>
 
@@ -203,8 +204,6 @@ sticky:
 	return ret;
 }
 
-
-
 #define FDS_IN(fds, n)		(fds->in + n)
 #define FDS_OUT(fds, n)		(fds->out + n)
 #define FDS_EX(fds, n)		(fds->ex + n)
@@ -257,11 +256,12 @@ get_max:
 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 #define POLLEX_SET (POLLPRI)
 
-int do_select(int n, fd_set_bits *fds, s64 *timeout)
+int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 {
+	ktime_t expire, *to = NULL;
 	struct poll_wqueues table;
 	poll_table *wait;
-	int retval, i;
+	int retval, i, timed_out = 0;
 
 	rcu_read_lock();
 	retval = max_select_fd(n, fds);
@@ -273,12 +273,14 @@ int do_select(int n, fd_set_bits *fds, s64 *timeout)
 
 	poll_initwait(&table);
 	wait = &table.pt;
-	if (!*timeout)
+	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 		wait = NULL;
+		timed_out = 1;
+	}
+
 	retval = 0;
 	for (;;) {
 		unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
-		long __timeout;
 
 		set_current_state(TASK_INTERRUPTIBLE);
 
@@ -334,27 +336,25 @@ int do_select(int n, fd_set_bits *fds, s64 *timeout)
 			cond_resched();
 		}
 		wait = NULL;
-		if (retval || !*timeout || signal_pending(current))
+		if (retval || timed_out || signal_pending(current))
 			break;
 		if (table.error) {
 			retval = table.error;
 			break;
 		}
 
-		if (*timeout < 0) {
-			/* Wait indefinitely */
-			__timeout = MAX_SCHEDULE_TIMEOUT;
-		} else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT - 1)) {
-			/* Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in a loop */
-			__timeout = MAX_SCHEDULE_TIMEOUT - 1;
-			*timeout -= __timeout;
-		} else {
-			__timeout = *timeout;
-			*timeout = 0;
+		/*
+		 * If this is the first loop and we have a timeout
+		 * given, then we convert to ktime_t and set the to
+		 * pointer to the expiry value.
+		 */
+		if (end_time && !to) {
+			expire = timespec_to_ktime(*end_time);
+			to = &expire;
 		}
-		__timeout = schedule_timeout(__timeout);
-		if (*timeout >= 0)
-			*timeout += __timeout;
+
+		if (!schedule_hrtimeout(to, HRTIMER_MODE_ABS))
+			timed_out = 1;
 	}
 	__set_current_state(TASK_RUNNING);
 
@@ -375,7 +375,7 @@ int do_select(int n, fd_set_bits *fds, s64 *timeout)
 	((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 
 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)
 {
 	fd_set_bits fds;
 	void *bits;
@@ -426,7 +426,7 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 	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;
@@ -452,7 +452,7 @@ out_nofds:
 asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 			fd_set __user *exp, struct timeval __user *tvp)
 {
-	s64 timeout = -1;
+	struct timespec end_time, *to = NULL;
 	struct timeval tv;
 	int ret;
 
@@ -460,43 +460,14 @@ asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 		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, USEC_PER_SEC/HZ);
-			timeout += tv.tv_sec * HZ;
-		}
 	}
 
-	ret = core_sys_select(n, inp, outp, exp, &timeout);
-
-	if (tvp) {
-		struct 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 (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 = core_sys_select(n, inp, outp, exp, to);
+	ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 
 	return ret;
 }
@@ -506,25 +477,17 @@ asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp,
 		fd_set __user *exp, struct timespec __user *tsp,
 		const sigset_t __user *sigmask, size_t sigsetsize)
 {
-	s64 timeout = MAX_SCHEDULE_TIMEOUT;
 	sigset_t ksigmask, sigsaved;
-	struct timespec ts;
+	struct timespec ts, 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;
-
-		/* Cast to u64 to make GCC stop complaining */
-		if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
-			timeout = -1;	/* infinite */
-		else {
-			timeout = DIV_ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
-			timeout += ts.tv_sec * HZ;
-		}
 	}
 
 	if (sigmask) {
@@ -538,32 +501,8 @@ asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp,
 		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 	}
 
-	ret = core_sys_select(n, inp, outp, exp, &timeout);
-
-	if (tsp) {
-		struct timespec rts;
-
-		if (current->personality & STICKY_TIMEOUTS)
-			goto sticky;
-		rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
-						1000;
-		rts.tv_sec = timeout;
-		if (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 = core_sys_select(n, inp, outp, exp, &end_time);
+	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 
 	if (ret == -ERESTARTNOHAND) {
 		/*
@@ -649,18 +588,20 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
 }
 
 static int do_poll(unsigned int nfds,  struct poll_list *list,
-		   struct poll_wqueues *wait, s64 *timeout)
+		   struct poll_wqueues *wait, struct timespec *end_time)
 {
-	int count = 0;
 	poll_table* pt = &wait->pt;
+	ktime_t expire, *to = NULL;
+	int timed_out = 0, count = 0;
 
 	/* Optimise the no-wait case */
-	if (!(*timeout))
+	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 		pt = NULL;
+		timed_out = 1;
+	}
 
 	for (;;) {
 		struct poll_list *walk;
-		long __timeout;
 
 		set_current_state(TASK_INTERRUPTIBLE);
 		for (walk = list; walk != NULL; walk = walk->next) {
@@ -692,27 +633,21 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 			if (signal_pending(current))
 				count = -EINTR;
 		}
-		if (count || !*timeout)
+		if (count || timed_out)
 			break;
 
-		if (*timeout < 0) {
-			/* Wait indefinitely */
-			__timeout = MAX_SCHEDULE_TIMEOUT;
-		} else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT-1)) {
-			/*
-			 * Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in
-			 * a loop
-			 */
-			__timeout = MAX_SCHEDULE_TIMEOUT - 1;
-			*timeout -= __timeout;
-		} else {
-			__timeout = *timeout;
-			*timeout = 0;
+		/*
+		 * If this is the first loop and we have a timeout
+		 * given, then we convert to ktime_t and set the to
+		 * pointer to the expiry value.
+		 */
+		if (end_time && !to) {
+			expire = timespec_to_ktime(*end_time);
+			to = &expire;
 		}
 
-		__timeout = schedule_timeout(__timeout);
-		if (*timeout >= 0)
-			*timeout += __timeout;
+		if (!schedule_hrtimeout(to, HRTIMER_MODE_ABS))
+			timed_out = 1;
 	}
 	__set_current_state(TASK_RUNNING);
 	return count;
@@ -721,7 +656,8 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 			sizeof(struct pollfd))
 
-int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
+int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
+		struct timespec *end_time)
 {
 	struct poll_wqueues table;
  	int err = -EFAULT, fdcount, len, size;
@@ -761,7 +697,7 @@ int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
 	}
 
 	poll_initwait(&table);
-	fdcount = do_poll(nfds, head, &table, timeout);
+	fdcount = do_poll(nfds, head, &table, end_time);
 	poll_freewait(&table);
 
 	for (walk = head; walk; walk = walk->next) {
@@ -787,16 +723,21 @@ out_fds:
 
 static long do_restart_poll(struct restart_block *restart_block)
 {
-	struct pollfd __user *ufds = (struct pollfd __user*)restart_block->arg0;
-	int nfds = restart_block->arg1;
-	s64 timeout = ((s64)restart_block->arg3<<32) | (s64)restart_block->arg2;
+	struct pollfd __user *ufds = restart_block->poll.ufds;
+	int nfds = restart_block->poll.nfds;
+	struct timespec *to = NULL, end_time;
 	int ret;
 
-	ret = do_sys_poll(ufds, nfds, &timeout);
+	if (restart_block->poll.has_timeout) {
+		end_time.tv_sec = restart_block->poll.tv_sec;
+		end_time.tv_nsec = restart_block->poll.tv_nsec;
+		to = &end_time;
+	}
+
+	ret = do_sys_poll(ufds, nfds, to);
+
 	if (ret == -EINTR) {
 		restart_block->fn = do_restart_poll;
-		restart_block->arg2 = timeout & 0xFFFFFFFF;
-		restart_block->arg3 = (u64)timeout >> 32;
 		ret = -ERESTART_RESTARTBLOCK;
 	}
 	return ret;
@@ -805,31 +746,32 @@ static long do_restart_poll(struct restart_block *restart_block)
 asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 			long timeout_msecs)
 {
-	s64 timeout_jiffies;
+	struct timespec end_time, *to = NULL;
 	int ret;
 
-	if (timeout_msecs > 0) {
-#if HZ > 1000
-		/* We can only overflow if HZ > 1000 */
-		if (timeout_msecs / 1000 > (s64)0x7fffffffffffffffULL / (s64)HZ)
-			timeout_jiffies = -1;
-		else
-#endif
-			timeout_jiffies = msecs_to_jiffies(timeout_msecs) + 1;
-	} else {
-		/* Infinite (< 0) or no (0) timeout */
-		timeout_jiffies = timeout_msecs;
+	if (timeout_msecs >= 0) {
+		to = &end_time;
+		poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
+			NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 	}
 
-	ret = do_sys_poll(ufds, nfds, &timeout_jiffies);
+	ret = do_sys_poll(ufds, nfds, to);
+
 	if (ret == -EINTR) {
 		struct restart_block *restart_block;
+
 		restart_block = &current_thread_info()->restart_block;
 		restart_block->fn = do_restart_poll;
-		restart_block->arg0 = (unsigned long)ufds;
-		restart_block->arg1 = nfds;
-		restart_block->arg2 = timeout_jiffies & 0xFFFFFFFF;
-		restart_block->arg3 = (u64)timeout_jiffies >> 32;
+		restart_block->poll.ufds = ufds;
+		restart_block->poll.nfds = nfds;
+
+		if (timeout_msecs >= 0) {
+			restart_block->poll.tv_sec = end_time.tv_sec;
+			restart_block->poll.tv_nsec = end_time.tv_nsec;
+			restart_block->poll.has_timeout = 1;
+		} else
+			restart_block->poll.has_timeout = 0;
+
 		ret = -ERESTART_RESTARTBLOCK;
 	}
 	return ret;
@@ -841,21 +783,16 @@ asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
 	size_t sigsetsize)
 {
 	sigset_t ksigmask, sigsaved;
-	struct timespec ts;
-	s64 timeout = -1;
+	struct timespec ts, end_time, *to = NULL;
 	int ret;
 
 	if (tsp) {
 		if (copy_from_user(&ts, tsp, sizeof(ts)))
 			return -EFAULT;
 
-		/* Cast to u64 to make GCC stop complaining */
-		if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
-			timeout = -1;	/* infinite */
-		else {
-			timeout = DIV_ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/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) {
@@ -869,7 +806,7 @@ asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
 		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) {
@@ -887,31 +824,7 @@ asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
 	} else if (sigmask)
 		sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 
-	if (tsp && timeout >= 0) {
-		struct 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 (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;
 }