On Mon, 25 Sep 2017, Luck, Tony wrote:
> On Mon, Sep 25, 2017 at 04:04:07PM +0200, Thomas Gleixner wrote:
> > On Mon, 18 Sep 2017, Luck, Tony wrote:
> > > @@ -208,14 +241,19 @@ ssize_t rdtgroup_schemata_write(struct
> > > kernfs_open_file *of,
> > > char *tok, *resname;
> > > int closid, ret = 0;
> > >
> > > + seq_buf_clear(&last_cmd_status);
> > > +
> > > /* Valid input requires a trailing newline */
> > > - if (nbytes == 0 || buf[nbytes - 1] != '\n')
> > > + if (nbytes == 0 || buf[nbytes - 1] != '\n') {
> > > + seq_buf_puts(&last_cmd_status, "no trailing newline\n");
> > > return -EINVAL;
> > > + }
> > > buf[nbytes - 1] = '\0';
> >
> > In all other instances you access last_cmd_status within the
> > rdtgroup_kn_lock_live() protected section, which also serializes the show()
> > function via rdtgroup_mutex. Here you do it outside for obvious reasons,
> > but that opens a can of evil worms ...
>
> Indeed.
>
> > Can you please provide and use two helpers - last_cmd_buf_clear() and
> > last_cmd_buf_puts() - which both have a
> > lockdep_assert_held(&rdtgroup_mutex) inside to make sure that we don't end
> > up with unprotected access accidentally?
>
> Sure. In progress. But I also need a last_cmd_printf(), which for some
> reason is giving me grief. In the header file I put:
>
> +static inline void last_cmd_printf(const char *fmt, ...)
> +{
> + va_list ap;
> +
> + va_start(ap, fmt);
> + lockdep_assert_held(&rdtgroup_mutex);
> + seq_buf_printf(&last_cmd_status, fmt, ap);
seq_buf_vprintf() is your friend. It takes va_list as last argument.
While at it can you please make it a proper function? No point for inlining
that.
Thanks,
tglx
