On Wed, Feb 25, 2015 at 03:32:08PM +0100, Cornelia Huck wrote: > On Wed, 25 Feb 2015 15:14:36 +0100 > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > virtio balloon has this code: > > wait_event_interruptible(vb->config_change, > > (diff = towards_target(vb)) != 0 > > || vb->need_stats_update > > || kthread_should_stop() > > || freezing(current)); > > > > Which is a problem because towards_target() call might block after > > wait_event_interruptible sets task state to TAST_INTERRUPTIBLE, causing > > the task_struct::state collision typical of nesting of sleeping > > primitives > > > > See also http://lwn.net/Articles/628628/ or Thomas's > > bug report > > http://article.gmane.org/gmane.linux.kernel.virtualization/24846 > > for a fuller explanation. > > > > To fix, rewrite using wait_woken. > > > > Cc: stable@xxxxxxxxxxxxxxx > > Reported-by: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx> > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > --- > > drivers/virtio/virtio_balloon.c | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > > index 0413157..2f19f65 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -29,6 +29,7 @@ > > #include <linux/module.h> > > #include <linux/balloon_compaction.h> > > #include <linux/oom.h> > > +#include <linux/wait.h> > > > > /* > > * Balloon device works in 4K page units. So each page is pointed to by > > @@ -334,12 +335,25 @@ static int virtballoon_oom_notify(struct notifier_block *self, > > static int balloon(void *_vballoon) > > { > > struct virtio_balloon *vb = _vballoon; > > + DEFINE_WAIT_FUNC(wait, woken_wake_function); > > > > set_freezable(); > > while (!kthread_should_stop()) { > > s64 diff; > > > > try_to_freeze(); > > + > > + add_wait_queue(&vb->config_change, &wait); > > + for (;;) { > > + if ((diff = towards_target(vb)) != 0 || > > + vb->need_stats_update || > > + kthread_should_stop() || > > + freezing(current)) > > + break; > > + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); > > + } > > + remove_wait_queue(&vb->config_change, &wait); > > + > > wait_event_interruptible(vb->config_change, > > (diff = towards_target(vb)) != 0 > > || vb->need_stats_update > > Forgot to remove the wait_event_interruptible()? Ugh. Forgot to commit :( Will resend. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
