fs/select.c - android_kernel_htc_msm8960 - Gitiles

 /*
  * This file contains the procedures for the handling of select and poll
  *
  * Created for Linux based loosely upon Mathius Lattner's minix
  * patches by Peter MacDonald. Heavily edited by Linus.
  *
  *  4 February 1994
  *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
  *     flag set in its personality we do *not* modify the given timeout
  *     parameter to reflect time remaining.
  *
  *  24 January 2000
  *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
  *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
  */

 #include <linux/kernel.h>
 #include <linux/syscalls.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
 #include <linux/file.h>
 #include <linux/fdtable.h>
 #include <linux/fs.h>
 #include <linux/rcupdate.h>
 #include <linux/hrtimer.h>

 #include <asm/uaccess.h>


 /*
  * Estimate expected accuracy in ns from a timeval.
  *
  * After quite a bit of churning around, we've settled on
  * a simple thing of taking 0.1% of the timeout as the
  * slack, with a cap of 100 msec.
  * "nice" tasks get a 0.5% slack instead.
  *
  * Consider this comment an open invitation to come up with even
  * better solutions..
  */

 static long __estimate_accuracy(struct timespec *tv)
 {
 	long slack;
 	int divfactor = 1000;

 	if (task_nice(current) > 0)
 		divfactor = divfactor / 5;

 	slack = tv->tv_nsec / divfactor;
 	slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);

 	if (slack > 100 * NSEC_PER_MSEC)
 		slack =  100 * NSEC_PER_MSEC;

 	if (slack < 0)
 		slack = 0;
 	return slack;
 }

 static long estimate_accuracy(struct timespec *tv)
 {
 	unsigned long ret;
 	struct timespec now;

 	/*
 	 * Realtime tasks get a slack of 0 for obvious reasons.
 	 */

 	if (rt_task(current))
 		return 0;

 	ktime_get_ts(&now);
 	now = timespec_sub(*tv, now);
 	ret = __estimate_accuracy(&now);
 	if (ret < current->timer_slack_ns)
 		return current->timer_slack_ns;
 	return ret;
 }


 struct poll_table_page {
 	struct poll_table_page * next;
 	struct poll_table_entry * entry;
 	struct poll_table_entry entries[0];
 };

 #define POLL_TABLE_FULL(table) \
 	((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))

 /*
  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
  * I have rewritten this, taking some shortcuts: This code may not be easy to
  * follow, but it should be free of race-conditions, and it's practical. If you
  * understand what I'm doing here, then you understand how the linux
  * sleep/wakeup mechanism works.
  *
  * Two very simple procedures, poll_wait() and poll_freewait() make all the
  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
  * as all select/poll functions have to call it to add an entry to the
  * poll table.
  */
 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 		       poll_table *p);

 void poll_initwait(struct poll_wqueues *pwq)
 {
 	init_poll_funcptr(&pwq->pt, __pollwait);
 	pwq->error = 0;
 	pwq->table = NULL;
 	pwq->inline_index = 0;
 }

 EXPORT_SYMBOL(poll_initwait);

 static void free_poll_entry(struct poll_table_entry *entry)
 {
 	remove_wait_queue(entry->wait_address, &entry->wait);
 	fput(entry->filp);
 }

 void poll_freewait(struct poll_wqueues *pwq)
 {
 	struct poll_table_page * p = pwq->table;
 	int i;
 	for (i = 0; i < pwq->inline_index; i++)
 		free_poll_entry(pwq->inline_entries + i);
 	while (p) {
 		struct poll_table_entry * entry;
 		struct poll_table_page *old;

 		entry = p->entry;
 		do {
 			entry--;
 			free_poll_entry(entry);
 		} while (entry > p->entries);
 		old = p;
 		p = p->next;
 		free_page((unsigned long) old);
 	}
 }

 EXPORT_SYMBOL(poll_freewait);

 static struct poll_table_entry *poll_get_entry(poll_table *_p)
 {
 	struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
 	struct poll_table_page *table = p->table;

 	if (p->inline_index < N_INLINE_POLL_ENTRIES)
 		return p->inline_entries + p->inline_index++;

 	if (!table || POLL_TABLE_FULL(table)) {
 		struct poll_table_page *new_table;

 		new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 		if (!new_table) {
 			p->error = -ENOMEM;
 			__set_current_state(TASK_RUNNING);
 			return NULL;
 		}
 		new_table->entry = new_table->entries;
 		new_table->next = table;
 		p->table = new_table;
 		table = new_table;
 	}

 	return table->entry++;
 }

 /* Add a new entry */
 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 				poll_table *p)
 {
 	struct poll_table_entry *entry = poll_get_entry(p);
 	if (!entry)
 		return;
 	get_file(filp);
 	entry->filp = filp;
 	entry->wait_address = wait_address;
 	init_waitqueue_entry(&entry->wait, current);
 	add_wait_queue(wait_address, &entry->wait);
 }

 /**
  * poll_select_set_timeout - helper function to setup the timeout value
  * @to:		pointer to timespec variable for the final timeout
  * @sec:	seconds (from user space)
  * @nsec:	nanoseconds (from user space)
  *
  * Note, we do not use a timespec for the user space value here, That
  * way we can use the function for timeval and compat interfaces as well.
  *
  * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
  */
 int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
 {
 	struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};

 	if (!timespec_valid(&ts))
 		return -EINVAL;

 	/* Optimize for the zero timeout value here */
 	if (!sec && !nsec) {
 		to->tv_sec = to->tv_nsec = 0;
 	} else {
 		ktime_get_ts(to);
 		*to = timespec_add_safe(*to, ts);
 	}
 	return 0;
 }

 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
 				      int timeval, int ret)
 {
 	struct timespec rts;
 	struct timeval rtv;

 	if (!p)
 		return ret;

 	if (current->personality & STICKY_TIMEOUTS)
 		goto sticky;

 	/* No update for zero timeout */
 	if (!end_time->tv_sec && !end_time->tv_nsec)
 		return ret;

 	ktime_get_ts(&rts);
 	rts = timespec_sub(*end_time, rts);
 	if (rts.tv_sec < 0)
 		rts.tv_sec = rts.tv_nsec = 0;

 	if (timeval) {
 		rtv.tv_sec = rts.tv_sec;
 		rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;

 		if (!copy_to_user(p, &rtv, sizeof(rtv)))
 			return ret;

 	} else if (!copy_to_user(p, &rts, sizeof(rts)))
 		return ret;

 	/*
 	 * 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.
 	 */

 sticky:
 	if (ret == -ERESTARTNOHAND)
 		ret = -EINTR;
 	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)

 #define BITS(fds, n)	(*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))

 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 {
 	unsigned long *open_fds;
 	unsigned long set;
 	int max;
 	struct fdtable *fdt;

 	/* handle last in-complete long-word first */
 	set = ~(~0UL << (n & (__NFDBITS-1)));
 	n /= __NFDBITS;
 	fdt = files_fdtable(current->files);
 	open_fds = fdt->open_fds->fds_bits+n;
 	max = 0;
 	if (set) {
 		set &= BITS(fds, n);
 		if (set) {
 			if (!(set & ~*open_fds))
 				goto get_max;
 			return -EBADF;
 		}
 	}
 	while (n) {
 		open_fds--;
 		n--;
 		set = BITS(fds, n);
 		if (!set)
 			continue;
 		if (set & ~*open_fds)
 			return -EBADF;
 		if (max)
 			continue;
 get_max:
 		do {
 			max++;
 			set >>= 1;
 		} while (set);
 		max += n * __NFDBITS;
 	}

 	return max;
 }

 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 #define POLLEX_SET (POLLPRI)

 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, timed_out = 0;
 	unsigned long slack = 0;

 	rcu_read_lock();
 	retval = max_select_fd(n, fds);
 	rcu_read_unlock();

 	if (retval < 0)
 		return retval;
 	n = retval;

 	poll_initwait(&table);
 	wait = &table.pt;
 	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 		wait = NULL;
 		timed_out = 1;
 	}

 	if (end_time && !timed_out)
 		slack = estimate_accuracy(end_time);

 	retval = 0;
 	for (;;) {
 		unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;

 		set_current_state(TASK_INTERRUPTIBLE);

 		inp = fds->in; outp = fds->out; exp = fds->ex;
 		rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;

 		for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 			unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 			unsigned long res_in = 0, res_out = 0, res_ex = 0;
 			const struct file_operations *f_op = NULL;
 			struct file *file = NULL;

 			in = *inp++; out = *outp++; ex = *exp++;
 			all_bits = in | out | ex;
 			if (all_bits == 0) {
 				i += __NFDBITS;
 				continue;
 			}

 			for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
 				int fput_needed;
 				if (i >= n)
 					break;
 				if (!(bit & all_bits))
 					continue;
 				file = fget_light(i, &fput_needed);
 				if (file) {
 					f_op = file->f_op;
 					mask = DEFAULT_POLLMASK;
 					if (f_op && f_op->poll)
 						mask = (*f_op->poll)(file, retval ? NULL : wait);
 					fput_light(file, fput_needed);
 					if ((mask & POLLIN_SET) && (in & bit)) {
 						res_in |= bit;
 						retval++;
 					}
 					if ((mask & POLLOUT_SET) && (out & bit)) {
 						res_out |= bit;
 						retval++;
 					}
 					if ((mask & POLLEX_SET) && (ex & bit)) {
 						res_ex |= bit;
 						retval++;
 					}
 				}
 			}
 			if (res_in)
 				*rinp = res_in;
 			if (res_out)
 				*routp = res_out;
 			if (res_ex)
 				*rexp = res_ex;
 			cond_resched();
 		}
 		wait = NULL;
 		if (retval || timed_out || signal_pending(current))
 			break;
 		if (table.error) {
 			retval = table.error;
 			break;
 		}

 		/*
 		 * 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;
 		}

 		if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
 			timed_out = 1;
 	}
 	__set_current_state(TASK_RUNNING);

 	poll_freewait(&table);

 	return retval;
 }

 /*
  * We can actually return ERESTARTSYS instead of EINTR, but I'd
  * like to be certain this leads to no problems. So I return
  * EINTR just for safety.
  *
  * Update: ERESTARTSYS breaks at least the xview clock binary, so
  * I'm trying ERESTARTNOHAND which restart only when you want to.
  */
 #define MAX_SELECT_SECONDS \
 	((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, struct timespec *end_time)
 {
 	fd_set_bits fds;
 	void *bits;
 	int ret, max_fds;
 	unsigned int size;
 	struct fdtable *fdt;
 	/* Allocate small arguments on the stack to save memory and be faster */
 	long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];

 	ret = -EINVAL;
 	if (n < 0)
 		goto out_nofds;

 	/* max_fds can increase, so grab it once to avoid race */
 	rcu_read_lock();
 	fdt = files_fdtable(current->files);
 	max_fds = fdt->max_fds;
 	rcu_read_unlock();
 	if (n > max_fds)
 		n = max_fds;

 	/*
 	 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 	 * since we used fdset we need to allocate memory in units of
 	 * long-words.
 	 */
 	size = FDS_BYTES(n);
 	bits = stack_fds;
 	if (size > sizeof(stack_fds) / 6) {
 		/* Not enough space in on-stack array; must use kmalloc */
 		ret = -ENOMEM;
 		bits = kmalloc(6 * size, GFP_KERNEL);
 		if (!bits)
 			goto out_nofds;
 	}
 	fds.in      = bits;
 	fds.out     = bits +   size;
 	fds.ex      = bits + 2*size;
 	fds.res_in  = bits + 3*size;
 	fds.res_out = bits + 4*size;
 	fds.res_ex  = bits + 5*size;

 	if ((ret = get_fd_set(n, inp, fds.in)) ||
 	    (ret = get_fd_set(n, outp, fds.out)) ||
 	    (ret = get_fd_set(n, exp, fds.ex)))
 		goto out;
 	zero_fd_set(n, fds.res_in);
 	zero_fd_set(n, fds.res_out);
 	zero_fd_set(n, fds.res_ex);

 	ret = do_select(n, &fds, end_time);

 	if (ret < 0)
 		goto out;
 	if (!ret) {
 		ret = -ERESTARTNOHAND;
 		if (signal_pending(current))
 			goto out;
 		ret = 0;
 	}

 	if (set_fd_set(n, inp, fds.res_in) ||
 	    set_fd_set(n, outp, fds.res_out) ||
 	    set_fd_set(n, exp, fds.res_ex))
 		ret = -EFAULT;

 out:
 	if (bits != stack_fds)
 		kfree(bits);
 out_nofds:
 	return ret;
 }

 asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 			fd_set __user *exp, struct timeval __user *tvp)
 {
 	struct timespec end_time, *to = NULL;
 	struct timeval tv;
 	int ret;

 	if (tvp) {
 		if (copy_from_user(&tv, tvp, sizeof(tv)))
 			return -EFAULT;

 		to = &end_time;
 		if (poll_select_set_timeout(to,
 				tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 				(tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 			return -EINVAL;
 	}

 	ret = core_sys_select(n, inp, outp, exp, to);
 	ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);

 	return ret;
 }

 #ifdef HAVE_SET_RESTORE_SIGMASK
 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)
 {
 	sigset_t ksigmask, sigsaved;
 	struct timespec ts, end_time, *to = NULL;
 	int ret;

 	if (tsp) {
 		if (copy_from_user(&ts, tsp, sizeof(ts)))
 			return -EFAULT;

 		to = &end_time;
 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 			return -EINVAL;
 	}

 	if (sigmask) {
 		/* XXX: Don't preclude handling different sized sigset_t's.  */
 		if (sigsetsize != sizeof(sigset_t))
 			return -EINVAL;
 		if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 			return -EFAULT;

 		sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 	}

 	ret = core_sys_select(n, inp, outp, exp, &end_time);
 	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);

 	if (ret == -ERESTARTNOHAND) {
 		/*
 		 * Don't restore the signal mask yet. Let do_signal() deliver
 		 * the signal on the way back to userspace, before the signal
 		 * mask is restored.
 		 */
 		if (sigmask) {
 			memcpy(&current->saved_sigmask, &sigsaved,
 					sizeof(sigsaved));
 			set_restore_sigmask();
 		}
 	} else if (sigmask)
 		sigprocmask(SIG_SETMASK, &sigsaved, NULL);

 	return ret;
 }

 /*
  * Most architectures can't handle 7-argument syscalls. So we provide a
  * 6-argument version where the sixth argument is a pointer to a structure
  * which has a pointer to the sigset_t itself followed by a size_t containing
  * the sigset size.
  */
 asmlinkage long sys_pselect6(int n, fd_set __user *inp, fd_set __user *outp,
 	fd_set __user *exp, struct timespec __user *tsp, void __user *sig)
 {
 	size_t sigsetsize = 0;
 	sigset_t __user *up = NULL;

 	if (sig) {
 		if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 		    || __get_user(up, (sigset_t __user * __user *)sig)
 		    || __get_user(sigsetsize,
 				(size_t __user *)(sig+sizeof(void *))))
 			return -EFAULT;
 	}

 	return sys_pselect7(n, inp, outp, exp, tsp, up, sigsetsize);
 }
 #endif /* HAVE_SET_RESTORE_SIGMASK */

 struct poll_list {
 	struct poll_list *next;
 	int len;
 	struct pollfd entries[0];
 };

 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))

 /*
  * Fish for pollable events on the pollfd->fd file descriptor. We're only
  * interested in events matching the pollfd->events mask, and the result
  * matching that mask is both recorded in pollfd->revents and returned. The
  * pwait poll_table will be used by the fd-provided poll handler for waiting,
  * if non-NULL.
  */
 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
 {
 	unsigned int mask;
 	int fd;

 	mask = 0;
 	fd = pollfd->fd;
 	if (fd >= 0) {
 		int fput_needed;
 		struct file * file;

 		file = fget_light(fd, &fput_needed);
 		mask = POLLNVAL;
 		if (file != NULL) {
 			mask = DEFAULT_POLLMASK;
 			if (file->f_op && file->f_op->poll)
 				mask = file->f_op->poll(file, pwait);
 			/* Mask out unneeded events. */
 			mask &= pollfd->events | POLLERR | POLLHUP;
 			fput_light(file, fput_needed);
 		}
 	}
 	pollfd->revents = mask;

 	return mask;
 }

 static int do_poll(unsigned int nfds,  struct poll_list *list,
 		   struct poll_wqueues *wait, struct timespec *end_time)
 {
 	poll_table* pt = &wait->pt;
 	ktime_t expire, *to = NULL;
 	int timed_out = 0, count = 0;
 	unsigned long slack = 0;

 	/* Optimise the no-wait case */
 	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 		pt = NULL;
 		timed_out = 1;
 	}

 	if (end_time && !timed_out)
 		slack = estimate_accuracy(end_time);

 	for (;;) {
 		struct poll_list *walk;

 		set_current_state(TASK_INTERRUPTIBLE);
 		for (walk = list; walk != NULL; walk = walk->next) {
 			struct pollfd * pfd, * pfd_end;

 			pfd = walk->entries;
 			pfd_end = pfd + walk->len;
 			for (; pfd != pfd_end; pfd++) {
 				/*
 				 * Fish for events. If we found one, record it
 				 * and kill the poll_table, so we don't
 				 * needlessly register any other waiters after
 				 * this. They'll get immediately deregistered
 				 * when we break out and return.
 				 */
 				if (do_pollfd(pfd, pt)) {
 					count++;
 					pt = NULL;
 				}
 			}
 		}
 		/*
 		 * All waiters have already been registered, so don't provide
 		 * a poll_table to them on the next loop iteration.
 		 */
 		pt = NULL;
 		if (!count) {
 			count = wait->error;
 			if (signal_pending(current))
 				count = -EINTR;
 		}
 		if (count || timed_out)
 			break;

 		/*
 		 * 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;
 		}

 		if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
 			timed_out = 1;
 	}
 	__set_current_state(TASK_RUNNING);
 	return count;
 }

 #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,
 		struct timespec *end_time)
 {
 	struct poll_wqueues table;
  	int err = -EFAULT, fdcount, len, size;
 	/* Allocate small arguments on the stack to save memory and be
 	   faster - use long to make sure the buffer is aligned properly
 	   on 64 bit archs to avoid unaligned access */
 	long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 	struct poll_list *const head = (struct poll_list *)stack_pps;
  	struct poll_list *walk = head;
  	unsigned long todo = nfds;

 	if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 		return -EINVAL;

 	len = min_t(unsigned int, nfds, N_STACK_PPS);
 	for (;;) {
 		walk->next = NULL;
 		walk->len = len;
 		if (!len)
 			break;

 		if (copy_from_user(walk->entries, ufds + nfds-todo,
 					sizeof(struct pollfd) * walk->len))
 			goto out_fds;

 		todo -= walk->len;
 		if (!todo)
 			break;

 		len = min(todo, POLLFD_PER_PAGE);
 		size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 		walk = walk->next = kmalloc(size, GFP_KERNEL);
 		if (!walk) {
 			err = -ENOMEM;
 			goto out_fds;
 		}
 	}

 	poll_initwait(&table);
 	fdcount = do_poll(nfds, head, &table, end_time);
 	poll_freewait(&table);

 	for (walk = head; walk; walk = walk->next) {
 		struct pollfd *fds = walk->entries;
 		int j;

 		for (j = 0; j < walk->len; j++, ufds++)
 			if (__put_user(fds[j].revents, &ufds->revents))
 				goto out_fds;
   	}

 	err = fdcount;
 out_fds:
 	walk = head->next;
 	while (walk) {
 		struct poll_list *pos = walk;
 		walk = walk->next;
 		kfree(pos);
 	}

 	return err;
 }

 static long do_restart_poll(struct restart_block *restart_block)
 {
 	struct pollfd __user *ufds = restart_block->poll.ufds;
 	int nfds = restart_block->poll.nfds;
 	struct timespec *to = NULL, end_time;
 	int ret;

 	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;
 		ret = -ERESTART_RESTARTBLOCK;
 	}
 	return ret;
 }

 asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 			long timeout_msecs)
 {
 	struct timespec end_time, *to = NULL;
 	int ret;

 	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, to);

 	if (ret == -EINTR) {
 		struct restart_block *restart_block;

 		restart_block = &current_thread_info()->restart_block;
 		restart_block->fn = do_restart_poll;
 		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;
 }

 #ifdef HAVE_SET_RESTORE_SIGMASK
 asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
 	struct timespec __user *tsp, const sigset_t __user *sigmask,
 	size_t sigsetsize)
 {
 	sigset_t ksigmask, sigsaved;
 	struct timespec ts, end_time, *to = NULL;
 	int ret;

 	if (tsp) {
 		if (copy_from_user(&ts, tsp, sizeof(ts)))
 			return -EFAULT;

 		to = &end_time;
 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 			return -EINVAL;
 	}

 	if (sigmask) {
 		/* XXX: Don't preclude handling different sized sigset_t's.  */
 		if (sigsetsize != sizeof(sigset_t))
 			return -EINVAL;
 		if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 			return -EFAULT;

 		sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 	}

 	ret = do_sys_poll(ufds, nfds, to);

 	/* We can restart this syscall, usually */
 	if (ret == -EINTR) {
 		/*
 		 * Don't restore the signal mask yet. Let do_signal() deliver
 		 * the signal on the way back to userspace, before the signal
 		 * mask is restored.
 		 */
 		if (sigmask) {
 			memcpy(&current->saved_sigmask, &sigsaved,
 					sizeof(sigsaved));
 			set_restore_sigmask();
 		}
 		ret = -ERESTARTNOHAND;
 	} else if (sigmask)
 		sigprocmask(SIG_SETMASK, &sigsaved, NULL);

 	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);

 	return ret;
 }
 #endif /* HAVE_SET_RESTORE_SIGMASK */
	/*
	* This file contains the procedures for the handling of select and poll
	*
	* Created for Linux based loosely upon Mathius Lattner's minix
	* patches by Peter MacDonald. Heavily edited by Linus.
	*
	* 4 February 1994
	* COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
	* flag set in its personality we do not modify the given timeout
	* parameter to reflect time remaining.
	*
	* 24 January 2000
	* Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
	* of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
	*/

	#include <linux/kernel.h>
	#include <linux/syscalls.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/poll.h>
	#include <linux/personality.h> /* for STICKY_TIMEOUTS */
	#include <linux/file.h>
	#include <linux/fdtable.h>
	#include <linux/fs.h>
	#include <linux/rcupdate.h>
	#include <linux/hrtimer.h>

	#include <asm/uaccess.h>


	/*
	* Estimate expected accuracy in ns from a timeval.
	*
	* After quite a bit of churning around, we've settled on
	* a simple thing of taking 0.1% of the timeout as the
	* slack, with a cap of 100 msec.
	* "nice" tasks get a 0.5% slack instead.
	*
	* Consider this comment an open invitation to come up with even
	* better solutions..
	*/

	static long __estimate_accuracy(struct timespec *tv)
	{
	long slack;
	int divfactor = 1000;

	if (task_nice(current) > 0)
	divfactor = divfactor / 5;

	slack = tv->tv_nsec / divfactor;
	slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);

	if (slack > 100 * NSEC_PER_MSEC)
	slack = 100 * NSEC_PER_MSEC;

	if (slack < 0)
	slack = 0;
	return slack;
	}

	static long estimate_accuracy(struct timespec *tv)
	{
	unsigned long ret;
	struct timespec now;

	/*
	* Realtime tasks get a slack of 0 for obvious reasons.
	*/

	if (rt_task(current))
	return 0;

	ktime_get_ts(&now);
	now = timespec_sub(*tv, now);
	ret = __estimate_accuracy(&now);
	if (ret < current->timer_slack_ns)
	return current->timer_slack_ns;
	return ret;
	}



	struct poll_table_page {
	struct poll_table_page * next;
	struct poll_table_entry * entry;
	struct poll_table_entry entries[0];
	};

	#define POLL_TABLE_FULL(table) \
	((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))

	/*
	* Ok, Peter made a complicated, but straightforward multiple_wait() function.
	* I have rewritten this, taking some shortcuts: This code may not be easy to
	* follow, but it should be free of race-conditions, and it's practical. If you
	* understand what I'm doing here, then you understand how the linux
	* sleep/wakeup mechanism works.
	*
	* Two very simple procedures, poll_wait() and poll_freewait() make all the
	* work. poll_wait() is an inline-function defined in <linux/poll.h>,
	* as all select/poll functions have to call it to add an entry to the
	* poll table.
	*/
	static void __pollwait(struct file filp, wait_queue_head_t wait_address,
	poll_table *p);

	void poll_initwait(struct poll_wqueues *pwq)
	{
	init_poll_funcptr(&pwq->pt, __pollwait);
	pwq->error = 0;
	pwq->table = NULL;
	pwq->inline_index = 0;
	}

	EXPORT_SYMBOL(poll_initwait);

	static void free_poll_entry(struct poll_table_entry *entry)
	{
	remove_wait_queue(entry->wait_address, &entry->wait);
	fput(entry->filp);
	}

	void poll_freewait(struct poll_wqueues *pwq)
	{
	struct poll_table_page * p = pwq->table;
	int i;
	for (i = 0; i < pwq->inline_index; i++)
	free_poll_entry(pwq->inline_entries + i);
	while (p) {
	struct poll_table_entry * entry;
	struct poll_table_page *old;

	entry = p->entry;
	do {
	entry--;
	free_poll_entry(entry);
	} while (entry > p->entries);
	old = p;
	p = p->next;
	free_page((unsigned long) old);
	}
	}

	EXPORT_SYMBOL(poll_freewait);

	static struct poll_table_entry poll_get_entry(poll_table _p)
	{
	struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
	struct poll_table_page *table = p->table;

	if (p->inline_index < N_INLINE_POLL_ENTRIES)
	return p->inline_entries + p->inline_index++;

	if (!table \|\| POLL_TABLE_FULL(table)) {
	struct poll_table_page *new_table;

	new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
	if (!new_table) {
	p->error = -ENOMEM;
	__set_current_state(TASK_RUNNING);
	return NULL;
	}
	new_table->entry = new_table->entries;
	new_table->next = table;
	p->table = new_table;
	table = new_table;
	}

	return table->entry++;
	}

	/* Add a new entry */
	static void __pollwait(struct file filp, wait_queue_head_t wait_address,
	poll_table *p)
	{
	struct poll_table_entry *entry = poll_get_entry(p);
	if (!entry)
	return;
	get_file(filp);
	entry->filp = filp;
	entry->wait_address = wait_address;
	init_waitqueue_entry(&entry->wait, current);
	add_wait_queue(wait_address, &entry->wait);
	}

	/**
	* poll_select_set_timeout - helper function to setup the timeout value
	* @to: pointer to timespec variable for the final timeout
	* @sec: seconds (from user space)
	* @nsec: nanoseconds (from user space)
	*
	* Note, we do not use a timespec for the user space value here, That
	* way we can use the function for timeval and compat interfaces as well.
	*
	* Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
	*/
	int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
	{
	struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};

	if (!timespec_valid(&ts))
	return -EINVAL;

	/* Optimize for the zero timeout value here */
	if (!sec && !nsec) {
	to->tv_sec = to->tv_nsec = 0;
	} else {
	ktime_get_ts(to);
	to = timespec_add_safe(to, ts);
	}
	return 0;
	}

	static int poll_select_copy_remaining(struct timespec end_time, void __user p,
	int timeval, int ret)
	{
	struct timespec rts;
	struct timeval rtv;

	if (!p)
	return ret;

	if (current->personality & STICKY_TIMEOUTS)
	goto sticky;

	/* No update for zero timeout */
	if (!end_time->tv_sec && !end_time->tv_nsec)
	return ret;

	ktime_get_ts(&rts);
	rts = timespec_sub(*end_time, rts);
	if (rts.tv_sec < 0)
	rts.tv_sec = rts.tv_nsec = 0;

	if (timeval) {
	rtv.tv_sec = rts.tv_sec;
	rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;

	if (!copy_to_user(p, &rtv, sizeof(rtv)))
	return ret;

	} else if (!copy_to_user(p, &rts, sizeof(rts)))
	return ret;

	/*
	* 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.
	*/

	sticky:
	if (ret == -ERESTARTNOHAND)
	ret = -EINTR;
	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)

	#define BITS(fds, n) (FDS_IN(fds, n)\|FDS_OUT(fds, n)\|*FDS_EX(fds, n))

	static int max_select_fd(unsigned long n, fd_set_bits *fds)
	{
	unsigned long *open_fds;
	unsigned long set;
	int max;
	struct fdtable *fdt;

	/* handle last in-complete long-word first */
	set = ~(~0UL << (n & (__NFDBITS-1)));
	n /= __NFDBITS;
	fdt = files_fdtable(current->files);
	open_fds = fdt->open_fds->fds_bits+n;
	max = 0;
	if (set) {
	set &= BITS(fds, n);
	if (set) {
	if (!(set & ~*open_fds))
	goto get_max;
	return -EBADF;
	}
	}
	while (n) {
	open_fds--;
	n--;
	set = BITS(fds, n);
	if (!set)
	continue;
	if (set & ~*open_fds)
	return -EBADF;
	if (max)
	continue;
	get_max:
	do {
	max++;
	set >>= 1;
	} while (set);
	max += n * __NFDBITS;
	}

	return max;
	}

	#define POLLIN_SET (POLLRDNORM \| POLLRDBAND \| POLLIN \| POLLHUP \| POLLERR)
	#define POLLOUT_SET (POLLWRBAND \| POLLWRNORM \| POLLOUT \| POLLERR)
	#define POLLEX_SET (POLLPRI)

	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, timed_out = 0;
	unsigned long slack = 0;

	rcu_read_lock();
	retval = max_select_fd(n, fds);
	rcu_read_unlock();

	if (retval < 0)
	return retval;
	n = retval;

	poll_initwait(&table);
	wait = &table.pt;
	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
	wait = NULL;
	timed_out = 1;
	}

	if (end_time && !timed_out)
	slack = estimate_accuracy(end_time);

	retval = 0;
	for (;;) {
	unsigned long rinp, routp, rexp, inp, outp, exp;

	set_current_state(TASK_INTERRUPTIBLE);

	inp = fds->in; outp = fds->out; exp = fds->ex;
	rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;

	for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
	unsigned long in, out, ex, all_bits, bit = 1, mask, j;
	unsigned long res_in = 0, res_out = 0, res_ex = 0;
	const struct file_operations *f_op = NULL;
	struct file *file = NULL;

	in = inp++; out = outp++; ex = *exp++;
	all_bits = in \| out \| ex;
	if (all_bits == 0) {
	i += __NFDBITS;
	continue;
	}

	for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
	int fput_needed;
	if (i >= n)
	break;
	if (!(bit & all_bits))
	continue;
	file = fget_light(i, &fput_needed);
	if (file) {
	f_op = file->f_op;
	mask = DEFAULT_POLLMASK;
	if (f_op && f_op->poll)
	mask = (*f_op->poll)(file, retval ? NULL : wait);
	fput_light(file, fput_needed);
	if ((mask & POLLIN_SET) && (in & bit)) {
	res_in \|= bit;
	retval++;
	}
	if ((mask & POLLOUT_SET) && (out & bit)) {
	res_out \|= bit;
	retval++;
	}
	if ((mask & POLLEX_SET) && (ex & bit)) {
	res_ex \|= bit;
	retval++;
	}
	}
	}
	if (res_in)
	*rinp = res_in;
	if (res_out)
	*routp = res_out;
	if (res_ex)
	*rexp = res_ex;
	cond_resched();
	}
	wait = NULL;
	if (retval \|\| timed_out \|\| signal_pending(current))
	break;
	if (table.error) {
	retval = table.error;
	break;
	}

	/*
	* 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;
	}

	if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
	timed_out = 1;
	}
	__set_current_state(TASK_RUNNING);

	poll_freewait(&table);

	return retval;
	}

	/*
	* We can actually return ERESTARTSYS instead of EINTR, but I'd
	* like to be certain this leads to no problems. So I return
	* EINTR just for safety.
	*
	* Update: ERESTARTSYS breaks at least the xview clock binary, so
	* I'm trying ERESTARTNOHAND which restart only when you want to.
	*/
	#define MAX_SELECT_SECONDS \
	((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, struct timespec end_time)
	{
	fd_set_bits fds;
	void *bits;
	int ret, max_fds;
	unsigned int size;
	struct fdtable *fdt;
	/* Allocate small arguments on the stack to save memory and be faster */
	long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];

	ret = -EINVAL;
	if (n < 0)
	goto out_nofds;

	/* max_fds can increase, so grab it once to avoid race */
	rcu_read_lock();
	fdt = files_fdtable(current->files);
	max_fds = fdt->max_fds;
	rcu_read_unlock();
	if (n > max_fds)
	n = max_fds;

	/*
	* We need 6 bitmaps (in/out/ex for both incoming and outgoing),
	* since we used fdset we need to allocate memory in units of
	* long-words.
	*/
	size = FDS_BYTES(n);
	bits = stack_fds;
	if (size > sizeof(stack_fds) / 6) {
	/* Not enough space in on-stack array; must use kmalloc */
	ret = -ENOMEM;
	bits = kmalloc(6 * size, GFP_KERNEL);
	if (!bits)
	goto out_nofds;
	}
	fds.in = bits;
	fds.out = bits + size;
	fds.ex = bits + 2*size;
	fds.res_in = bits + 3*size;
	fds.res_out = bits + 4*size;
	fds.res_ex = bits + 5*size;

	if ((ret = get_fd_set(n, inp, fds.in)) \|\|
	(ret = get_fd_set(n, outp, fds.out)) \|\|
	(ret = get_fd_set(n, exp, fds.ex)))
	goto out;
	zero_fd_set(n, fds.res_in);
	zero_fd_set(n, fds.res_out);
	zero_fd_set(n, fds.res_ex);

	ret = do_select(n, &fds, end_time);

	if (ret < 0)
	goto out;
	if (!ret) {
	ret = -ERESTARTNOHAND;
	if (signal_pending(current))
	goto out;
	ret = 0;
	}

	if (set_fd_set(n, inp, fds.res_in) \|\|
	set_fd_set(n, outp, fds.res_out) \|\|
	set_fd_set(n, exp, fds.res_ex))
	ret = -EFAULT;

	out:
	if (bits != stack_fds)
	kfree(bits);
	out_nofds:
	return ret;
	}

	asmlinkage long sys_select(int n, fd_set __user inp, fd_set __user outp,
	fd_set __user exp, struct timeval __user tvp)
	{
	struct timespec end_time, *to = NULL;
	struct timeval tv;
	int ret;

	if (tvp) {
	if (copy_from_user(&tv, tvp, sizeof(tv)))
	return -EFAULT;

	to = &end_time;
	if (poll_select_set_timeout(to,
	tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
	(tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
	return -EINVAL;
	}

	ret = core_sys_select(n, inp, outp, exp, to);
	ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);

	return ret;
	}

	#ifdef HAVE_SET_RESTORE_SIGMASK
	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)
	{
	sigset_t ksigmask, sigsaved;
	struct timespec ts, end_time, *to = NULL;
	int ret;

	if (tsp) {
	if (copy_from_user(&ts, tsp, sizeof(ts)))
	return -EFAULT;

	to = &end_time;
	if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
	return -EINVAL;
	}

	if (sigmask) {
	/* XXX: Don't preclude handling different sized sigset_t's. */
	if (sigsetsize != sizeof(sigset_t))
	return -EINVAL;
	if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
	return -EFAULT;

	sigdelsetmask(&ksigmask, sigmask(SIGKILL)\|sigmask(SIGSTOP));
	sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
	}

	ret = core_sys_select(n, inp, outp, exp, &end_time);
	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);

	if (ret == -ERESTARTNOHAND) {
	/*
	* Don't restore the signal mask yet. Let do_signal() deliver
	* the signal on the way back to userspace, before the signal
	* mask is restored.
	*/
	if (sigmask) {
	memcpy(&current->saved_sigmask, &sigsaved,
	sizeof(sigsaved));
	set_restore_sigmask();
	}
	} else if (sigmask)
	sigprocmask(SIG_SETMASK, &sigsaved, NULL);

	return ret;
	}

	/*
	* Most architectures can't handle 7-argument syscalls. So we provide a
	* 6-argument version where the sixth argument is a pointer to a structure
	* which has a pointer to the sigset_t itself followed by a size_t containing
	* the sigset size.
	*/
	asmlinkage long sys_pselect6(int n, fd_set __user inp, fd_set __user outp,
	fd_set __user exp, struct timespec __user tsp, void __user *sig)
	{
	size_t sigsetsize = 0;
	sigset_t __user *up = NULL;

	if (sig) {
	if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
	\|\| __get_user(up, (sigset_t __user * __user *)sig)
	\|\| __get_user(sigsetsize,
	(size_t __user )(sig+sizeof(void ))))
	return -EFAULT;
	}

	return sys_pselect7(n, inp, outp, exp, tsp, up, sigsetsize);
	}
	#endif /* HAVE_SET_RESTORE_SIGMASK */

	struct poll_list {
	struct poll_list *next;
	int len;
	struct pollfd entries[0];
	};

	#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))

	/*
	* Fish for pollable events on the pollfd->fd file descriptor. We're only
	* interested in events matching the pollfd->events mask, and the result
	* matching that mask is both recorded in pollfd->revents and returned. The
	* pwait poll_table will be used by the fd-provided poll handler for waiting,
	* if non-NULL.
	*/
	static inline unsigned int do_pollfd(struct pollfd pollfd, poll_table pwait)
	{
	unsigned int mask;
	int fd;

	mask = 0;
	fd = pollfd->fd;
	if (fd >= 0) {
	int fput_needed;
	struct file * file;

	file = fget_light(fd, &fput_needed);
	mask = POLLNVAL;
	if (file != NULL) {
	mask = DEFAULT_POLLMASK;
	if (file->f_op && file->f_op->poll)
	mask = file->f_op->poll(file, pwait);
	/* Mask out unneeded events. */
	mask &= pollfd->events \| POLLERR \| POLLHUP;
	fput_light(file, fput_needed);
	}
	}
	pollfd->revents = mask;

	return mask;
	}

	static int do_poll(unsigned int nfds, struct poll_list *list,
	struct poll_wqueues wait, struct timespec end_time)
	{
	poll_table* pt = &wait->pt;
	ktime_t expire, *to = NULL;
	int timed_out = 0, count = 0;
	unsigned long slack = 0;

	/* Optimise the no-wait case */
	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
	pt = NULL;
	timed_out = 1;
	}

	if (end_time && !timed_out)
	slack = estimate_accuracy(end_time);

	for (;;) {
	struct poll_list *walk;

	set_current_state(TASK_INTERRUPTIBLE);
	for (walk = list; walk != NULL; walk = walk->next) {
	struct pollfd * pfd, * pfd_end;

	pfd = walk->entries;
	pfd_end = pfd + walk->len;
	for (; pfd != pfd_end; pfd++) {
	/*
	* Fish for events. If we found one, record it
	* and kill the poll_table, so we don't
	* needlessly register any other waiters after
	* this. They'll get immediately deregistered
	* when we break out and return.
	*/
	if (do_pollfd(pfd, pt)) {
	count++;
	pt = NULL;
	}
	}
	}
	/*
	* All waiters have already been registered, so don't provide
	* a poll_table to them on the next loop iteration.
	*/
	pt = NULL;
	if (!count) {
	count = wait->error;
	if (signal_pending(current))
	count = -EINTR;
	}
	if (count \|\| timed_out)
	break;

	/*
	* 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;
	}

	if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
	timed_out = 1;
	}
	__set_current_state(TASK_RUNNING);
	return count;
	}

	#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,
	struct timespec *end_time)
	{
	struct poll_wqueues table;
	int err = -EFAULT, fdcount, len, size;
	/* Allocate small arguments on the stack to save memory and be
	faster - use long to make sure the buffer is aligned properly
	on 64 bit archs to avoid unaligned access */
	long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
	struct poll_list const head = (struct poll_list )stack_pps;
	struct poll_list *walk = head;
	unsigned long todo = nfds;

	if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
	return -EINVAL;

	len = min_t(unsigned int, nfds, N_STACK_PPS);
	for (;;) {
	walk->next = NULL;
	walk->len = len;
	if (!len)
	break;

	if (copy_from_user(walk->entries, ufds + nfds-todo,
	sizeof(struct pollfd) * walk->len))
	goto out_fds;

	todo -= walk->len;
	if (!todo)
	break;

	len = min(todo, POLLFD_PER_PAGE);
	size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
	walk = walk->next = kmalloc(size, GFP_KERNEL);
	if (!walk) {
	err = -ENOMEM;
	goto out_fds;
	}
	}

	poll_initwait(&table);
	fdcount = do_poll(nfds, head, &table, end_time);
	poll_freewait(&table);

	for (walk = head; walk; walk = walk->next) {
	struct pollfd *fds = walk->entries;
	int j;

	for (j = 0; j < walk->len; j++, ufds++)
	if (__put_user(fds[j].revents, &ufds->revents))
	goto out_fds;
	}

	err = fdcount;
	out_fds:
	walk = head->next;
	while (walk) {
	struct poll_list *pos = walk;
	walk = walk->next;
	kfree(pos);
	}

	return err;
	}

	static long do_restart_poll(struct restart_block *restart_block)
	{
	struct pollfd __user *ufds = restart_block->poll.ufds;
	int nfds = restart_block->poll.nfds;
	struct timespec *to = NULL, end_time;
	int ret;

	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;
	ret = -ERESTART_RESTARTBLOCK;
	}
	return ret;
	}

	asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
	long timeout_msecs)
	{
	struct timespec end_time, *to = NULL;
	int ret;

	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, to);

	if (ret == -EINTR) {
	struct restart_block *restart_block;

	restart_block = &current_thread_info()->restart_block;
	restart_block->fn = do_restart_poll;
	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;
	}

	#ifdef HAVE_SET_RESTORE_SIGMASK
	asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
	struct timespec __user tsp, const sigset_t __user sigmask,
	size_t sigsetsize)
	{
	sigset_t ksigmask, sigsaved;
	struct timespec ts, end_time, *to = NULL;
	int ret;

	if (tsp) {
	if (copy_from_user(&ts, tsp, sizeof(ts)))
	return -EFAULT;

	to = &end_time;
	if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
	return -EINVAL;
	}

	if (sigmask) {
	/* XXX: Don't preclude handling different sized sigset_t's. */
	if (sigsetsize != sizeof(sigset_t))
	return -EINVAL;
	if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
	return -EFAULT;

	sigdelsetmask(&ksigmask, sigmask(SIGKILL)\|sigmask(SIGSTOP));
	sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
	}

	ret = do_sys_poll(ufds, nfds, to);

	/* We can restart this syscall, usually */
	if (ret == -EINTR) {
	/*
	* Don't restore the signal mask yet. Let do_signal() deliver
	* the signal on the way back to userspace, before the signal
	* mask is restored.
	*/
	if (sigmask) {
	memcpy(&current->saved_sigmask, &sigsaved,
	sizeof(sigsaved));
	set_restore_sigmask();
	}
	ret = -ERESTARTNOHAND;
	} else if (sigmask)
	sigprocmask(SIG_SETMASK, &sigsaved, NULL);

	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);

	return ret;
	}
	#endif /* HAVE_SET_RESTORE_SIGMASK */