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);//调用poll_wait处理过程,即把驱动中等待队列头增加到poll_wqueues中的entry中,并把指向当前里程的等待队列项增加到等待队列头中。每一个等待队列头占用一个entry 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();//增加抢占点,调度其它进程,当前里程进入睡眠 }
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);