lkml.org 
[lkml]   [2010]   [Nov]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] sched: automated per session task groups
On 11/21, Ingo Molnar wrote:
>
> Btw., there's a small cleanup in the patch that i picked up (see below), and i also
> edited the commit log a bit - so you might want to pick up the version below.

I didn't read the patch in details, but a couple of nits...

> +static void
> +autogroup_move_group(struct task_struct *p, struct autogroup *ag)
> +{
> + struct autogroup *prev;
> + struct task_struct *t;
> +
> + spin_lock(&p->sighand->siglock);

This needs spin_lock_irq(), ->siglock is irq-safe.

The same for other lockers, but:

> +static inline struct autogroup *autogroup_get(struct task_struct *p)
> +{
> + struct autogroup *ag;
> +
> + /* task may be moved after we unlock.. tough */
> + spin_lock(&p->sighand->siglock);

This is called by fs/proc. In this case nothing protects us from
release_task(), we can hit ->siglock == NULL (or we can race with
exec which changes ->sighand in theory).

This needs lock_task_sighand() (it can fail). Perhaps something
else have the same problem...

If the task is current and it is not exiting, or it is the new
child (sched_autogroup_fork), then it is safe to use ->siglock
directly.

And a pure cosmetic nit,

> +void sched_autogroup_fork(struct signal_struct *sig)
> +{
> + struct sighand_struct *sighand = current->sighand;
> +
> + spin_lock(&sighand->siglock);
> + sig->autogroup = autogroup_kref_get(current->signal->autogroup);
> + spin_unlock(&sighand->siglock);
> +}

This looks a bit confusing. We do not need current->sighand->siglock
to set sig->autogroup. Nobody except us can see this new signal_struct,
and in any case current->sighand->siglock can't help.

It is needed for autogroup_kref_get(), but we already have autogroup_get().
I'd suggest

void sched_autogroup_fork(struct signal_struct *sig)
{
sig->autogroup = autogroup_get(current);
}

Oleg.



\
 
 \ /
  Last update: 2010-11-21 16:53    [W:0.149 / U:21.416 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site