2 * This file contains the procedures for the handling of select and poll
4 * Created for Linux based loosely upon Mathius Lattner's minix
5 * patches by Peter MacDonald. Heavily edited by Linus.
8 * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
9 * flag set in its personality we do *not* modify the given timeout
10 * parameter to reflect time remaining.
13 * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
14 * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
17 #include <linux/kernel.h>
18 #include <linux/syscalls.h>
19 #include <linux/module.h>
20 #include <linux/slab.h>
21 #include <linux/poll.h>
22 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
26 #include <linux/rcupdate.h>
27 #include <linux/hrtimer.h>
29 #include <asm/uaccess.h>
33 * Estimate expected accuracy in ns from a timeval.
35 * After quite a bit of churning around, we've settled on
36 * a simple thing of taking 0.1% of the timeout as the
37 * slack, with a cap of 100 msec.
38 * "nice" tasks get a 0.5% slack instead.
40 * Consider this comment an open invitation to come up with even
44 static long __estimate_accuracy(struct timespec
*tv
)
49 if (task_nice(current
) > 0)
50 divfactor
= divfactor
/ 5;
52 slack
= tv
->tv_nsec
/ divfactor
;
53 slack
+= tv
->tv_sec
* (NSEC_PER_SEC
/divfactor
);
55 if (slack
> 100 * NSEC_PER_MSEC
)
56 slack
= 100 * NSEC_PER_MSEC
;
63 static long estimate_accuracy(struct timespec
*tv
)
69 * Realtime tasks get a slack of 0 for obvious reasons.
76 now
= timespec_sub(*tv
, now
);
77 ret
= __estimate_accuracy(&now
);
78 if (ret
< current
->timer_slack_ns
)
79 return current
->timer_slack_ns
;
85 struct poll_table_page
{
86 struct poll_table_page
* next
;
87 struct poll_table_entry
* entry
;
88 struct poll_table_entry entries
[0];
91 #define POLL_TABLE_FULL(table) \
92 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
95 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
96 * I have rewritten this, taking some shortcuts: This code may not be easy to
97 * follow, but it should be free of race-conditions, and it's practical. If you
98 * understand what I'm doing here, then you understand how the linux
99 * sleep/wakeup mechanism works.
101 * Two very simple procedures, poll_wait() and poll_freewait() make all the
102 * work. poll_wait() is an inline-function defined in <linux/poll.h>,
103 * as all select/poll functions have to call it to add an entry to the
106 static void __pollwait(struct file
*filp
, wait_queue_head_t
*wait_address
,
109 void poll_initwait(struct poll_wqueues
*pwq
)
111 init_poll_funcptr(&pwq
->pt
, __pollwait
);
114 pwq
->inline_index
= 0;
117 EXPORT_SYMBOL(poll_initwait
);
119 static void free_poll_entry(struct poll_table_entry
*entry
)
121 remove_wait_queue(entry
->wait_address
, &entry
->wait
);
125 void poll_freewait(struct poll_wqueues
*pwq
)
127 struct poll_table_page
* p
= pwq
->table
;
129 for (i
= 0; i
< pwq
->inline_index
; i
++)
130 free_poll_entry(pwq
->inline_entries
+ i
);
132 struct poll_table_entry
* entry
;
133 struct poll_table_page
*old
;
138 free_poll_entry(entry
);
139 } while (entry
> p
->entries
);
142 free_page((unsigned long) old
);
146 EXPORT_SYMBOL(poll_freewait
);
148 static struct poll_table_entry
*poll_get_entry(poll_table
*_p
)
150 struct poll_wqueues
*p
= container_of(_p
, struct poll_wqueues
, pt
);
151 struct poll_table_page
*table
= p
->table
;
153 if (p
->inline_index
< N_INLINE_POLL_ENTRIES
)
154 return p
->inline_entries
+ p
->inline_index
++;
156 if (!table
|| POLL_TABLE_FULL(table
)) {
157 struct poll_table_page
*new_table
;
159 new_table
= (struct poll_table_page
*) __get_free_page(GFP_KERNEL
);
162 __set_current_state(TASK_RUNNING
);
165 new_table
->entry
= new_table
->entries
;
166 new_table
->next
= table
;
167 p
->table
= new_table
;
171 return table
->entry
++;
174 /* Add a new entry */
175 static void __pollwait(struct file
*filp
, wait_queue_head_t
*wait_address
,
178 struct poll_table_entry
*entry
= poll_get_entry(p
);
183 entry
->wait_address
= wait_address
;
184 init_waitqueue_entry(&entry
->wait
, current
);
185 add_wait_queue(wait_address
, &entry
->wait
);
189 * poll_select_set_timeout - helper function to setup the timeout value
190 * @to: pointer to timespec variable for the final timeout
191 * @sec: seconds (from user space)
192 * @nsec: nanoseconds (from user space)
194 * Note, we do not use a timespec for the user space value here, That
195 * way we can use the function for timeval and compat interfaces as well.
197 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
199 int poll_select_set_timeout(struct timespec
*to
, long sec
, long nsec
)
201 struct timespec ts
= {.tv_sec
= sec
, .tv_nsec
= nsec
};
203 if (!timespec_valid(&ts
))
206 /* Optimize for the zero timeout value here */
208 to
->tv_sec
= to
->tv_nsec
= 0;
211 *to
= timespec_add_safe(*to
, ts
);
216 static int poll_select_copy_remaining(struct timespec
*end_time
, void __user
*p
,
217 int timeval
, int ret
)
225 if (current
->personality
& STICKY_TIMEOUTS
)
228 /* No update for zero timeout */
229 if (!end_time
->tv_sec
&& !end_time
->tv_nsec
)
233 rts
= timespec_sub(*end_time
, rts
);
235 rts
.tv_sec
= rts
.tv_nsec
= 0;
238 rtv
.tv_sec
= rts
.tv_sec
;
239 rtv
.tv_usec
= rts
.tv_nsec
/ NSEC_PER_USEC
;
241 if (!copy_to_user(p
, &rtv
, sizeof(rtv
)))
244 } else if (!copy_to_user(p
, &rts
, sizeof(rts
)))
248 * If an application puts its timeval in read-only memory, we
249 * don't want the Linux-specific update to the timeval to
250 * cause a fault after the select has completed
251 * successfully. However, because we're not updating the
252 * timeval, we can't restart the system call.
256 if (ret
== -ERESTARTNOHAND
)
261 #define FDS_IN(fds, n) (fds->in + n)
262 #define FDS_OUT(fds, n) (fds->out + n)
263 #define FDS_EX(fds, n) (fds->ex + n)
265 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
267 static int max_select_fd(unsigned long n
, fd_set_bits
*fds
)
269 unsigned long *open_fds
;
274 /* handle last in-complete long-word first */
275 set
= ~(~0UL << (n
& (__NFDBITS
-1)));
277 fdt
= files_fdtable(current
->files
);
278 open_fds
= fdt
->open_fds
->fds_bits
+n
;
283 if (!(set
& ~*open_fds
))
294 if (set
& ~*open_fds
)
303 max
+= n
* __NFDBITS
;
309 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
310 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
311 #define POLLEX_SET (POLLPRI)
313 int do_select(int n
, fd_set_bits
*fds
, struct timespec
*end_time
)
315 ktime_t expire
, *to
= NULL
;
316 struct poll_wqueues table
;
318 int retval
, i
, timed_out
= 0;
319 unsigned long slack
= 0;
322 retval
= max_select_fd(n
, fds
);
329 poll_initwait(&table
);
331 if (end_time
&& !end_time
->tv_sec
&& !end_time
->tv_nsec
) {
336 if (end_time
&& !timed_out
)
337 slack
= estimate_accuracy(end_time
);
341 unsigned long *rinp
, *routp
, *rexp
, *inp
, *outp
, *exp
;
343 set_current_state(TASK_INTERRUPTIBLE
);
345 inp
= fds
->in
; outp
= fds
->out
; exp
= fds
->ex
;
346 rinp
= fds
->res_in
; routp
= fds
->res_out
; rexp
= fds
->res_ex
;
348 for (i
= 0; i
< n
; ++rinp
, ++routp
, ++rexp
) {
349 unsigned long in
, out
, ex
, all_bits
, bit
= 1, mask
, j
;
350 unsigned long res_in
= 0, res_out
= 0, res_ex
= 0;
351 const struct file_operations
*f_op
= NULL
;
352 struct file
*file
= NULL
;
354 in
= *inp
++; out
= *outp
++; ex
= *exp
++;
355 all_bits
= in
| out
| ex
;
361 for (j
= 0; j
< __NFDBITS
; ++j
, ++i
, bit
<<= 1) {
365 if (!(bit
& all_bits
))
367 file
= fget_light(i
, &fput_needed
);
370 mask
= DEFAULT_POLLMASK
;
371 if (f_op
&& f_op
->poll
)
372 mask
= (*f_op
->poll
)(file
, retval
? NULL
: wait
);
373 fput_light(file
, fput_needed
);
374 if ((mask
& POLLIN_SET
) && (in
& bit
)) {
378 if ((mask
& POLLOUT_SET
) && (out
& bit
)) {
382 if ((mask
& POLLEX_SET
) && (ex
& bit
)) {
397 if (retval
|| timed_out
|| signal_pending(current
))
400 retval
= table
.error
;
405 * If this is the first loop and we have a timeout
406 * given, then we convert to ktime_t and set the to
407 * pointer to the expiry value.
409 if (end_time
&& !to
) {
410 expire
= timespec_to_ktime(*end_time
);
414 if (!schedule_hrtimeout_range(to
, slack
, HRTIMER_MODE_ABS
))
417 __set_current_state(TASK_RUNNING
);
419 poll_freewait(&table
);
425 * We can actually return ERESTARTSYS instead of EINTR, but I'd
426 * like to be certain this leads to no problems. So I return
427 * EINTR just for safety.
429 * Update: ERESTARTSYS breaks at least the xview clock binary, so
430 * I'm trying ERESTARTNOHAND which restart only when you want to.
432 #define MAX_SELECT_SECONDS \
433 ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
435 int core_sys_select(int n
, fd_set __user
*inp
, fd_set __user
*outp
,
436 fd_set __user
*exp
, struct timespec
*end_time
)
443 /* Allocate small arguments on the stack to save memory and be faster */
444 long stack_fds
[SELECT_STACK_ALLOC
/sizeof(long)];
450 /* max_fds can increase, so grab it once to avoid race */
452 fdt
= files_fdtable(current
->files
);
453 max_fds
= fdt
->max_fds
;
459 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
460 * since we used fdset we need to allocate memory in units of
465 if (size
> sizeof(stack_fds
) / 6) {
466 /* Not enough space in on-stack array; must use kmalloc */
468 bits
= kmalloc(6 * size
, GFP_KERNEL
);
473 fds
.out
= bits
+ size
;
474 fds
.ex
= bits
+ 2*size
;
475 fds
.res_in
= bits
+ 3*size
;
476 fds
.res_out
= bits
+ 4*size
;
477 fds
.res_ex
= bits
+ 5*size
;
479 if ((ret
= get_fd_set(n
, inp
, fds
.in
)) ||
480 (ret
= get_fd_set(n
, outp
, fds
.out
)) ||
481 (ret
= get_fd_set(n
, exp
, fds
.ex
)))
483 zero_fd_set(n
, fds
.res_in
);
484 zero_fd_set(n
, fds
.res_out
);
485 zero_fd_set(n
, fds
.res_ex
);
487 ret
= do_select(n
, &fds
, end_time
);
492 ret
= -ERESTARTNOHAND
;
493 if (signal_pending(current
))
498 if (set_fd_set(n
, inp
, fds
.res_in
) ||
499 set_fd_set(n
, outp
, fds
.res_out
) ||
500 set_fd_set(n
, exp
, fds
.res_ex
))
504 if (bits
!= stack_fds
)
510 asmlinkage
long sys_select(int n
, fd_set __user
*inp
, fd_set __user
*outp
,
511 fd_set __user
*exp
, struct timeval __user
*tvp
)
513 struct timespec end_time
, *to
= NULL
;
518 if (copy_from_user(&tv
, tvp
, sizeof(tv
)))
522 if (poll_select_set_timeout(to
, tv
.tv_sec
,
523 tv
.tv_usec
* NSEC_PER_USEC
))
527 ret
= core_sys_select(n
, inp
, outp
, exp
, to
);
528 ret
= poll_select_copy_remaining(&end_time
, tvp
, 1, ret
);
533 #ifdef HAVE_SET_RESTORE_SIGMASK
534 asmlinkage
long sys_pselect7(int n
, fd_set __user
*inp
, fd_set __user
*outp
,
535 fd_set __user
*exp
, struct timespec __user
*tsp
,
536 const sigset_t __user
*sigmask
, size_t sigsetsize
)
538 sigset_t ksigmask
, sigsaved
;
539 struct timespec ts
, end_time
, *to
= NULL
;
543 if (copy_from_user(&ts
, tsp
, sizeof(ts
)))
547 if (poll_select_set_timeout(to
, ts
.tv_sec
, ts
.tv_nsec
))
552 /* XXX: Don't preclude handling different sized sigset_t's. */
553 if (sigsetsize
!= sizeof(sigset_t
))
555 if (copy_from_user(&ksigmask
, sigmask
, sizeof(ksigmask
)))
558 sigdelsetmask(&ksigmask
, sigmask(SIGKILL
)|sigmask(SIGSTOP
));
559 sigprocmask(SIG_SETMASK
, &ksigmask
, &sigsaved
);
562 ret
= core_sys_select(n
, inp
, outp
, exp
, &end_time
);
563 ret
= poll_select_copy_remaining(&end_time
, tsp
, 0, ret
);
565 if (ret
== -ERESTARTNOHAND
) {
567 * Don't restore the signal mask yet. Let do_signal() deliver
568 * the signal on the way back to userspace, before the signal
572 memcpy(¤t
->saved_sigmask
, &sigsaved
,
574 set_restore_sigmask();
577 sigprocmask(SIG_SETMASK
, &sigsaved
, NULL
);
583 * Most architectures can't handle 7-argument syscalls. So we provide a
584 * 6-argument version where the sixth argument is a pointer to a structure
585 * which has a pointer to the sigset_t itself followed by a size_t containing
588 asmlinkage
long sys_pselect6(int n
, fd_set __user
*inp
, fd_set __user
*outp
,
589 fd_set __user
*exp
, struct timespec __user
*tsp
, void __user
*sig
)
591 size_t sigsetsize
= 0;
592 sigset_t __user
*up
= NULL
;
595 if (!access_ok(VERIFY_READ
, sig
, sizeof(void *)+sizeof(size_t))
596 || __get_user(up
, (sigset_t __user
* __user
*)sig
)
597 || __get_user(sigsetsize
,
598 (size_t __user
*)(sig
+sizeof(void *))))
602 return sys_pselect7(n
, inp
, outp
, exp
, tsp
, up
, sigsetsize
);
604 #endif /* HAVE_SET_RESTORE_SIGMASK */
607 struct poll_list
*next
;
609 struct pollfd entries
[0];
612 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
615 * Fish for pollable events on the pollfd->fd file descriptor. We're only
616 * interested in events matching the pollfd->events mask, and the result
617 * matching that mask is both recorded in pollfd->revents and returned. The
618 * pwait poll_table will be used by the fd-provided poll handler for waiting,
621 static inline unsigned int do_pollfd(struct pollfd
*pollfd
, poll_table
*pwait
)
632 file
= fget_light(fd
, &fput_needed
);
635 mask
= DEFAULT_POLLMASK
;
636 if (file
->f_op
&& file
->f_op
->poll
)
637 mask
= file
->f_op
->poll(file
, pwait
);
638 /* Mask out unneeded events. */
639 mask
&= pollfd
->events
| POLLERR
| POLLHUP
;
640 fput_light(file
, fput_needed
);
643 pollfd
->revents
= mask
;
648 static int do_poll(unsigned int nfds
, struct poll_list
*list
,
649 struct poll_wqueues
*wait
, struct timespec
*end_time
)
651 poll_table
* pt
= &wait
->pt
;
652 ktime_t expire
, *to
= NULL
;
653 int timed_out
= 0, count
= 0;
654 unsigned long slack
= 0;
656 /* Optimise the no-wait case */
657 if (end_time
&& !end_time
->tv_sec
&& !end_time
->tv_nsec
) {
662 if (end_time
&& !timed_out
)
663 slack
= estimate_accuracy(end_time
);
666 struct poll_list
*walk
;
668 set_current_state(TASK_INTERRUPTIBLE
);
669 for (walk
= list
; walk
!= NULL
; walk
= walk
->next
) {
670 struct pollfd
* pfd
, * pfd_end
;
673 pfd_end
= pfd
+ walk
->len
;
674 for (; pfd
!= pfd_end
; pfd
++) {
676 * Fish for events. If we found one, record it
677 * and kill the poll_table, so we don't
678 * needlessly register any other waiters after
679 * this. They'll get immediately deregistered
680 * when we break out and return.
682 if (do_pollfd(pfd
, pt
)) {
689 * All waiters have already been registered, so don't provide
690 * a poll_table to them on the next loop iteration.
695 if (signal_pending(current
))
698 if (count
|| timed_out
)
702 * If this is the first loop and we have a timeout
703 * given, then we convert to ktime_t and set the to
704 * pointer to the expiry value.
706 if (end_time
&& !to
) {
707 expire
= timespec_to_ktime(*end_time
);
711 if (!schedule_hrtimeout_range(to
, slack
, HRTIMER_MODE_ABS
))
714 __set_current_state(TASK_RUNNING
);
718 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
719 sizeof(struct pollfd))
721 int do_sys_poll(struct pollfd __user
*ufds
, unsigned int nfds
,
722 struct timespec
*end_time
)
724 struct poll_wqueues table
;
725 int err
= -EFAULT
, fdcount
, len
, size
;
726 /* Allocate small arguments on the stack to save memory and be
727 faster - use long to make sure the buffer is aligned properly
728 on 64 bit archs to avoid unaligned access */
729 long stack_pps
[POLL_STACK_ALLOC
/sizeof(long)];
730 struct poll_list
*const head
= (struct poll_list
*)stack_pps
;
731 struct poll_list
*walk
= head
;
732 unsigned long todo
= nfds
;
734 if (nfds
> current
->signal
->rlim
[RLIMIT_NOFILE
].rlim_cur
)
737 len
= min_t(unsigned int, nfds
, N_STACK_PPS
);
744 if (copy_from_user(walk
->entries
, ufds
+ nfds
-todo
,
745 sizeof(struct pollfd
) * walk
->len
))
752 len
= min(todo
, POLLFD_PER_PAGE
);
753 size
= sizeof(struct poll_list
) + sizeof(struct pollfd
) * len
;
754 walk
= walk
->next
= kmalloc(size
, GFP_KERNEL
);
761 poll_initwait(&table
);
762 fdcount
= do_poll(nfds
, head
, &table
, end_time
);
763 poll_freewait(&table
);
765 for (walk
= head
; walk
; walk
= walk
->next
) {
766 struct pollfd
*fds
= walk
->entries
;
769 for (j
= 0; j
< walk
->len
; j
++, ufds
++)
770 if (__put_user(fds
[j
].revents
, &ufds
->revents
))
778 struct poll_list
*pos
= walk
;
786 static long do_restart_poll(struct restart_block
*restart_block
)
788 struct pollfd __user
*ufds
= restart_block
->poll
.ufds
;
789 int nfds
= restart_block
->poll
.nfds
;
790 struct timespec
*to
= NULL
, end_time
;
793 if (restart_block
->poll
.has_timeout
) {
794 end_time
.tv_sec
= restart_block
->poll
.tv_sec
;
795 end_time
.tv_nsec
= restart_block
->poll
.tv_nsec
;
799 ret
= do_sys_poll(ufds
, nfds
, to
);
802 restart_block
->fn
= do_restart_poll
;
803 ret
= -ERESTART_RESTARTBLOCK
;
808 asmlinkage
long sys_poll(struct pollfd __user
*ufds
, unsigned int nfds
,
811 struct timespec end_time
, *to
= NULL
;
814 if (timeout_msecs
>= 0) {
816 poll_select_set_timeout(to
, timeout_msecs
/ MSEC_PER_SEC
,
817 NSEC_PER_MSEC
* (timeout_msecs
% MSEC_PER_SEC
));
820 ret
= do_sys_poll(ufds
, nfds
, to
);
823 struct restart_block
*restart_block
;
825 restart_block
= ¤t_thread_info()->restart_block
;
826 restart_block
->fn
= do_restart_poll
;
827 restart_block
->poll
.ufds
= ufds
;
828 restart_block
->poll
.nfds
= nfds
;
830 if (timeout_msecs
>= 0) {
831 restart_block
->poll
.tv_sec
= end_time
.tv_sec
;
832 restart_block
->poll
.tv_nsec
= end_time
.tv_nsec
;
833 restart_block
->poll
.has_timeout
= 1;
835 restart_block
->poll
.has_timeout
= 0;
837 ret
= -ERESTART_RESTARTBLOCK
;
842 #ifdef HAVE_SET_RESTORE_SIGMASK
843 asmlinkage
long sys_ppoll(struct pollfd __user
*ufds
, unsigned int nfds
,
844 struct timespec __user
*tsp
, const sigset_t __user
*sigmask
,
847 sigset_t ksigmask
, sigsaved
;
848 struct timespec ts
, end_time
, *to
= NULL
;
852 if (copy_from_user(&ts
, tsp
, sizeof(ts
)))
856 if (poll_select_set_timeout(to
, ts
.tv_sec
, ts
.tv_nsec
))
861 /* XXX: Don't preclude handling different sized sigset_t's. */
862 if (sigsetsize
!= sizeof(sigset_t
))
864 if (copy_from_user(&ksigmask
, sigmask
, sizeof(ksigmask
)))
867 sigdelsetmask(&ksigmask
, sigmask(SIGKILL
)|sigmask(SIGSTOP
));
868 sigprocmask(SIG_SETMASK
, &ksigmask
, &sigsaved
);
871 ret
= do_sys_poll(ufds
, nfds
, to
);
873 /* We can restart this syscall, usually */
876 * Don't restore the signal mask yet. Let do_signal() deliver
877 * the signal on the way back to userspace, before the signal
881 memcpy(¤t
->saved_sigmask
, &sigsaved
,
883 set_restore_sigmask();
885 ret
= -ERESTARTNOHAND
;
887 sigprocmask(SIG_SETMASK
, &sigsaved
, NULL
);
889 ret
= poll_select_copy_remaining(&end_time
, tsp
, 0, ret
);
893 #endif /* HAVE_SET_RESTORE_SIGMASK */
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