Subject: [PATCH UPDATED 3/3] vhost: apply cpumask and cgroup to vhost pollers

From: Tejun Heo <[email-masked]>
Date: Mon, 31 May 2010 08:58:42 +0200

Apply the cpumask and cgroup of the initializing task to the created
vhost poller.

Based on Sridhar Samudrala's patch.  Li Zefan spotted a bug in error
path, fixed.

Cc: Michael S. Tsirkin <[email-masked]>
Cc: Sridhar Samudrala <[email-masked]>
Cc: Li Zefan <[email-masked]>
---
Updated accordingly.  Thanks.

 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 && poller)
+		kthread_stop(poller);
+	free_cpumask_var(mask);
+	return ret;
 }

 /* Caller should have device mutex */