[Devel] Re: [PATCH 2/2] [RFC] Enable non-blocking writes to the cgroup freezer.state file

[Matt Helsley]

On Mon, Oct 26, 2009 at 08:15:30AM -0700, Matt Helsley wrote:

<snip>

> The change to the num_cant_freeze_now count enables blocking
> while the test of dont_block outside of all the locks re-enables
> non-blocking operations when O_NONBLOCK is set.

nit:

Oops, forgot to update the portion of the description above. Should
read:

The change to the num_cant_freeze_now count enables blocking 
while the test of f_flags & O_NONBLOCK outside of all the locks ...

<snip>

> @@ -356,10 +354,22 @@ static int freezer_write(struct cgroup *cgroup, struct cftype *cft,
>  	else
>  		return -EINVAL;
> 
> +retry:
>  	if (!cgroup_lock_live_group(cgroup))
>  		return -ENODEV;
>  	retval = freezer_change_state(cgroup, goal_state);
>  	cgroup_unlock();
> +
> +	if ((f_flags & O_NONBLOCK) || (retval != -EAGAIN))
> +		return retval;
> +
> +	/* block while we haven't changed the state to the goal state */
> +	set_current_state(TASK_INTERRUPTIBLE);
> +	schedule();
> +	__set_current_state(TASK_RUNNING);
> +	if (!signal_pending(current))
> +		goto retry;
> +	retval = -EINTR;
>  	return retval;
>  }

Cheers,
	-Matt Helsley
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