Re: [PATCH] timer_list: Correct the show function for timer_listby using iter->now

[Nathan Zimmer]

On 07/23/2013 02:18 AM, Holger Hans Peter Freyther wrote:
> On Mon, Jul 22, 2013 at 04:18:31PM -0500, Nathan Zimmer wrote:
> > This patch corrects the issue with /proc/timer_list reported by Holger.
> > When reading from the proc file with a sufficently small buffer, 2k so not
> > really that small, there was one could get hung trying to read the file a
> > chunk at a time.
> I think it makes sense to always use iter->now but it does not solve
> the issue with dropbear/my test case. Or is this meant to be applied
> on top of the previous patch?
>
>
> holger
Ah sorry I networked booted the wrong kernel and got excited.


However after hitting my head against this for the better part of the 
day I found
the root cause of my issue.

In seq_read about halfway down when we flush the buffer to userland.
m->index is advanced without calling m->op->next().
My iterator doesn't take notice of that and thus fails to advance.

        /* if not empty - flush it first */
        if (m->count) {
                n = min(m->count, size);
                err = copy_to_user(buf, m->buf + m->from, n);
                if (err)
                        goto Efault;
                m->count -= n;
                m->from += n;
                size -= n;
                buf += n;
                copied += n;
                if (!m->count)
                        m->index++;
....


I'll need to think about how to correct it.

For the moment probably the right thing would be to revert b3956a896ea5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/