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    SubjectRe: [PATCH 3/3] vhost: apply cpumask and cgroup to vhost pollers
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    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@redhat.com>
    > > Cc: Sridhar Samudrala <samudrala.sridhar@gmail.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@us.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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