linux-kernel - Re: [PATCH 3/3] vhost: apply cpumask and cgroup to vhost pollers

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Message-Id: <1277419551.27868.27.camel@w-sridhar.beaverton.ibm.com>
Date:	Thu, 24 Jun 2010 15:45:51 -0700
From:	Sridhar Samudrala <sri@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	netdev <netdev@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitri Vorobiev <dmitri.vorobiev@...ial.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 3/3] vhost: apply cpumask and cgroup to vhost pollers

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 <mst@...hat.com>
> > Cc: Sridhar Samudrala <samudrala.sridhar@...il.com>
> 
> 
> 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 <sri@...ibm.com>

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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