Subject: [PATCH] sched: export sched_set/getaffinity (was Re: [PATCH 3/3] vhost: apply cpumask and cgroup to vhost pollers)

From: "Michael S. Tsirkin" <[email-masked]>
Date: Fri, 25 Jun 2010 13:10:22 +0300

On Thu, Jun 24, 2010 at 03:45:51PM -0700, Sridhar Samudrala wrote:
> On Thu, 2010-06-24 at 11:11 +0300, Michael S. Tsirkin wrote:
> > On Sun, May 30, 2010 at 10:25:01PM +0200, Tejun Heo wrote:
> > > Apply the cpumask and cgroup of the initializing task to the created
> > > vhost poller.
> > > 
> > > Based on Sridhar Samudrala's patch.
> > > 
> > > Cc: Michael S. Tsirkin <[email-masked]>
> > > Cc: Sridhar Samudrala <[email-masked]>
> > 
> > 
> > I wanted to apply this, but modpost fails:
> > ERROR: "sched_setaffinity" [drivers/vhost/vhost_net.ko] undefined!
> > ERROR: "sched_getaffinity" [drivers/vhost/vhost_net.ko] undefined!
> > 
> > Did you try building as a module?
> 
> In my original implementation, i had these calls in workqueue.c.
> Now that these are moved to vhost.c which can be built as a module,
> these symbols need to be exported.
> The following patch fixes the build issue with vhost as a module.
> 
> Signed-off-by: Sridhar Samudrala <[email-masked]>

Signed-off-by: Michael S. Tsirkin <[email-masked]>

Works for me. To simplify dependencies, I'd like to queue this
together with the chost patches through net-next.
Ack to this?

> diff --git a/kernel/sched.c b/kernel/sched.c
> index 3c2a54f..15a0c6f 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4837,6 +4837,7 @@ out_put_task:
>  	put_online_cpus();
>  	return retval;
>  }
> +EXPORT_SYMBOL_GPL(sched_setaffinity);
>  
>  static int get_user_cpu_mask(unsigned long __user *user_mask_ptr,
> unsigned len,
>  			     struct cpumask *new_mask)
> @@ -4900,6 +4901,7 @@ out_unlock:
>  
>  	return retval;
>  }
> +EXPORT_SYMBOL_GPL(sched_getaffinity);
>  
>  /**
>   * sys_sched_getaffinity - get the cpu affinity of a process
> 
> 
> > > ---
> > >  drivers/vhost/vhost.c |   36 +++++++++++++++++++++++++++++++-----
> > >  1 file changed, 31 insertions(+), 5 deletions(-)
> > > 
> > > Index: work/drivers/vhost/vhost.c
> > > ===================================================================
> > > --- work.orig/drivers/vhost/vhost.c
> > > +++ work/drivers/vhost/vhost.c
> > > @@ -23,6 +23,7 @@
> > >  #include <linux/highmem.h>
> > >  #include <linux/slab.h>
> > >  #include <linux/kthread.h>
> > > +#include <linux/cgroup.h>
> > > 
> > >  #include <linux/net.h>
> > >  #include <linux/if_packet.h>
> > > @@ -176,12 +177,30 @@ repeat:
> > >  long vhost_dev_init(struct vhost_dev *dev,
> > >  		    struct vhost_virtqueue *vqs, int nvqs)
> > >  {
> > > -	struct task_struct *poller;
> > > -	int i;
> > > +	struct task_struct *poller = NULL;
> > > +	cpumask_var_t mask;
> > > +	int i, ret = -ENOMEM;
> > > +
> > > +	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
> > > +		goto out;
> > > 
> > >  	poller = kthread_create(vhost_poller, dev, "vhost-%d", current->pid);
> > > -	if (IS_ERR(poller))
> > > -		return PTR_ERR(poller);
> > > +	if (IS_ERR(poller)) {
> > > +		ret = PTR_ERR(poller);
> > > +		goto out;
> > > +	}
> > > +
> > > +	ret = sched_getaffinity(current->pid, mask);
> > > +	if (ret)
> > > +		goto out;
> > > +
> > > +	ret = sched_setaffinity(poller->pid, mask);
> > > +	if (ret)
> > > +		goto out;
> > > +
> > > +	ret = cgroup_attach_task_current_cg(poller);
> > > +	if (ret)
> > > +		goto out;
> > > 
> > >  	dev->vqs = vqs;
> > >  	dev->nvqs = nvqs;
> > > @@ -202,7 +221,14 @@ long vhost_dev_init(struct vhost_dev *de
> > >  			vhost_poll_init(&dev->vqs[i].poll,
> > >  					dev->vqs[i].handle_kick, POLLIN, dev);
> > >  	}
> > > -	return 0;
> > > +
> > > +	wake_up_process(poller);	/* avoid contributing to loadavg */
> > > +	ret = 0;
> > > +out:
> > > +	if (ret)
> > > +		kthread_stop(poller);
> > > +	free_cpumask_var(mask);
> > > +	return ret;
> > >  }
> > > 
> > >  /* Caller should have device mutex */
> > --
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