linux-master/fs/select.c

11  *     parameter to reflect time remaining.
14  *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
15  *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
47  * Consider this comment an open invitation to come up with even
109  * I have rewritten this, taking some shortcuts: This code may not be easy to
116  * as all select/poll functions have to call it to add an entry to the
194 	 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
204 	 * TODO: This is hacky but there currently is no interface to
205 	 * pass in @sync.  @sync is scheduled to be removed and once
264  * poll_select_set_timeout - helper function to setup the timeout value
265  * @to:		pointer to timespec64 variable for the final timeout
274 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec)
283 		to->tv_sec = to->tv_nsec = 0;
285 		ktime_get_ts64(to);
286 		*to = timespec64_add_safe(*to, ts);
358 	 * don't want the Linux-specific update to the timeval to
387  * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
481 	ktime_t expire, *to = NULL;
599 		 * given, then we convert to ktime_t and set the to
600 		 * pointer to the expiry value.
602 		if (end_time && !to) {
604 			to = &expire;
608 					   to, slack))
619  * like to be certain this leads to no problems. So I return
623  * I'm trying ERESTARTNOHAND which restart only when you want to.
633 	/* Allocate small arguments on the stack to save memory and be faster */
640 	/* max_fds can increase, so grab it once to avoid race */
650 	 * since we used fdset we need to allocate memory in units of
707 	struct timespec64 end_time, *to = NULL;
715 		to = &end_time;
716 		if (poll_select_set_timeout(to,
722 	ret = core_sys_select(n, inp, outp, exp, to);
737 	struct timespec64 ts, end_time, *to = NULL;
754 		to = &end_time;
755 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
763 	ret = core_sys_select(n, inp, outp, exp, to);
769  * 6-argument version where the sixth argument is a pointer to a structure
770  * which has a pointer to the sigset_t itself followed by a size_t containing
778 static inline int get_sigset_argpack(struct sigset_argpack *to,
781 	// the path is hot enough for overhead of copy_from_user() to matter
785 		unsafe_get_user(to->p, &from->p, Efault);
786 		unsafe_get_user(to->size, &from->size, Efault);
889 	ktime_t expire, *to = NULL;
933 		 * a poll_table->_qproc to them on the next loop iteration.
957 		 * given, then we convert to ktime_t and set the to
958 		 * pointer to the expiry value.
960 		if (end_time && !to) {
962 			to = &expire;
965 		if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
979 	/* Allocate small arguments on the stack to save memory and be
980 	   faster - use long to make sure the buffer is aligned properly
981 	   on 64 bit archs to avoid unaligned access */
1052 	struct timespec64 *to = NULL, end_time;
1058 		to = &end_time;
1061 	ret = do_sys_poll(ufds, nfds, to);
1072 	struct timespec64 end_time, *to = NULL;
1076 		to = &end_time;
1077 		poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
1081 	ret = do_sys_poll(ufds, nfds, to);
1106 	struct timespec64 ts, end_time, *to = NULL;
1113 		to = &end_time;
1114 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1122 	ret = do_sys_poll(ufds, nfds, to);
1132 	struct timespec64 ts, end_time, *to = NULL;
1139 		to = &end_time;
1140 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1148 	ret = do_sys_poll(ufds, nfds, to);
1157  * Ooo, nasty.  We need here to frob 32-bit unsigned longs to
1184  * should be compared to it from time to time
1189  * like to be certain this leads to no problems. So I return
1193  * I'm trying ERESTARTNOHAND which restart only when you want to.
1208 	/* max_fds can increase, so grab it once to avoid race */
1218 	 * since we used fdset we need to allocate memory in units of
1270 	struct timespec64 end_time, *to = NULL;
1278 		to = &end_time;
1279 		if (poll_select_set_timeout(to,
1285 	ret = compat_core_sys_select(n, inp, outp, exp, to);
1319 	struct timespec64 ts, end_time, *to = NULL;
1336 		to = &end_time;
1337 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1345 	ret = compat_core_sys_select(n, inp, outp, exp, to);
1353 static inline int get_compat_sigset_argpack(struct compat_sigset_argpack *to,
1359 		unsafe_get_user(to->p, &from->p, Efault);
1360 		unsafe_get_user(to->size, &from->size, Efault);
1404 	struct timespec64 ts, end_time, *to = NULL;
1411 		to = &end_time;
1412 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1420 	ret = do_sys_poll(ufds, nfds, to);
1430 	struct timespec64 ts, end_time, *to = NULL;
1437 		to = &end_time;
1438 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1446 	ret = do_sys_poll(ufds, nfds, to);