On Thu, 2014-06-19 at 19:24 -0400, Pranith Kumar wrote:
> (dropping some CCs)
>
> On 06/19/2014 05:00 PM, Paul E. McKenney wrote:
> > On Wed, Jun 18, 2014 at 12:49:42PM -0700, Joe Perches wrote:
> >>
> >> I believe the function doesn't work well.
> >>
> >> static void
> >> rcu_torture_stats_print(void)
> >> {
> >> int size = nr_cpu_ids * 200 + 8192;
> >> char *buf;
> >>
> >> buf = kmalloc(size, GFP_KERNEL);
> >> if (!buf) {
> >> pr_err("rcu-torture: Out of memory, need: %d\n", size);
> >> return;
> >> }
> >> rcu_torture_printk(buf);
> >> pr_alert("%s", buf);
> >> kfree(buf);
> >> }
> >>
> >> rcu_torture_printk simply fills buf
> >>
> >> btw: I believe the arguments should pass size and
> >> rcu_torture_printk should use snprintf/size
> >>
> >> but all printks are limited to a maximum of 1024
> >> bytes so the large allocation is senseless and
> >> would even if it worked, would likely need to be
> >> vmalloc/vfree
> >
> > Fair point!
> >
> > Pranith, Romanov, if you would like part of RCU that is less touchy
> > about random hacking, this would be a good place to start. Scripts in
> > tools/testing/selftests/rcutorture/bin do care about some of the format,
> > but the variable-length portion generated by cur_ops->stats() is as far
> > as I know only parsed by human eyes.
> >
>
> Here is a first run of the change. Please let me know if I am totally off.
> RFC. :)
>
> Three things on Todo list:
>
> * We need to check that we are using less than the allocated size of the
> buffer (used > size). (we are allocating a big buffer, so not sure if
> necessary)
> * Need to check with the scripts if they are working.
> * I used a loop for pr_alert(). I am not sure this is right, there should be
> a better way for printing large buffers
>
> If the overall structure is ok I will go ahead and check how the scripts are
> handling these changes.
[]
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
[]
> @@ -1130,17 +1134,23 @@ rcu_torture_printk(char *page)
> static void
> rcu_torture_stats_print(void)
> {
[]
> + /* printk can print only print LOG_LINE_MAX chars at a time */
> + while (used > 0) {
> + size_pr = pr_alert("%s", buf);
> + used -= size_pr;
> + buf += size_pr;
> + }
> + vfree(buf);
> }
You can't increment buf then vfree it.
Try a char *tmpbuf = buf, and increment it.
I suggest you check by strcspn(tmpbuf, "\n")
save the byte after, replace it with 0,
print, replace the 0 with saved byte, and
loop until end of buffer.
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