> > > static int uptime_read_proc(char *page, char **start, off_t off,
> > > int count, int *eof, void *data)
> > > {
> > > struct timespec uptime;
> > > struct timespec idle;
> > > int len;
> > > cputime_t idletime;
> > >
> > > + if (off)
> > > + return 0;
> >
> > Except that this is wrong - if you try to advance the offset a bit from
> > the start of the file and read something, you'll get nothing. This is
> > inconsistent with normal file behavior.
>
> so what - "uptime_read_proc" ignores the offset parameter anyway.
> you get wrong results right now, too, even without the two lines
> I've added.
>
> if you write "Except that this is wrong" you should have in mind that
> "this is wrong" currently, too.
>
> just "try to advance the offset a bit from the start of the file and
> read something", like "dd if=/proc/uptime bs=1 count=1 seek=1".
> do you expect to get right results?
argh, my mistake, sorry. I see. I tried reading a character at a time
and with the two lines, /proc/uptime will return only a single character.
so even though currently the update-routine is called more than
needed, my patch is even more wrong.
but this means that e.g.:
int main() {
int fd;
char ch;
fd=open("/proc/uptime",0);
for(;;) {
if (read(fd,&ch,1)!=1)
break;
write(1,&ch,1);
}
}
will call the buffer-formatting routines 16 times on the whole
buffer, just to return 1 single character, and each call will
return a different result. eeks...
by the way: why does "dd if=/proc/uptime bs=1 seek=1" hang?
e.g.:
root@afp ~ # strace -f dd if=/proc/uptime bs=1 count=1 seek=1
open("/proc/uptime", O_RDONLY|O_LARGEFILE) = 0
...
_llseek(1, 1, 0xbfaa8464, SEEK_CUR) = -1 ESPIPE (Illegal seek)
read(1, <unfinished ...>
processing stops here.
regards,
h.rosmanith
regards,
h.rosmanith
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