| Message ID | 1424874878-17155-1-git-send-email-mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 25 Feb 2015 15:36:02 +0100 "Michael S. Tsirkin" <mst@redhat.com> 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@vger.kernel.org > Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > > changes from v1: > remove wait_event_interruptible > noticed by Cornelia Huck <cornelia.huck@de.ibm.com> > > drivers/virtio/virtio_balloon.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > I was able to reproduce Thomas' original problem and can confirm that it is gone with this patch. Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 25 Feb 2015 16:11:27 +0100 Cornelia Huck <cornelia.huck@de.ibm.com> wrote: > On Wed, 25 Feb 2015 15:36:02 +0100 > "Michael S. Tsirkin" <mst@redhat.com> 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@vger.kernel.org > > Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > > > changes from v1: > > remove wait_event_interruptible > > noticed by Cornelia Huck <cornelia.huck@de.ibm.com> > > > > drivers/virtio/virtio_balloon.c | 19 ++++++++++++++----- > > 1 file changed, 14 insertions(+), 5 deletions(-) > > > > I was able to reproduce Thomas' original problem and can confirm that > it is gone with this patch. > > Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> Right, I just applied the patch on my system, too, and the problem is indeed gone! Thanks for the quick fix! Tested-by: Thomas Huth <thuth@linux.vnet.ibm.com> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Thomas Huth <thuth@linux.vnet.ibm.com> writes: > On Wed, 25 Feb 2015 16:11:27 +0100 > Cornelia Huck <cornelia.huck@de.ibm.com> wrote: > >> On Wed, 25 Feb 2015 15:36:02 +0100 >> "Michael S. Tsirkin" <mst@redhat.com> 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@vger.kernel.org >> > Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com> >> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> >> > --- >> > >> > changes from v1: >> > remove wait_event_interruptible >> > noticed by Cornelia Huck <cornelia.huck@de.ibm.com> >> > >> > drivers/virtio/virtio_balloon.c | 19 ++++++++++++++----- >> > 1 file changed, 14 insertions(+), 5 deletions(-) >> > >> >> I was able to reproduce Thomas' original problem and can confirm that >> it is gone with this patch. >> >> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> > > Right, I just applied the patch on my system, too, and the problem is > indeed gone! Thanks for the quick fix! > > Tested-by: Thomas Huth <thuth@linux.vnet.ibm.com> Applied. Thanks, Rusty. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 0413157..5a6ad6d 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 @@ -334,17 +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(); - wait_event_interruptible(vb->config_change, - (diff = towards_target(vb)) != 0 - || vb->need_stats_update - || kthread_should_stop() - || freezing(current)); + + 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); + if (vb->need_stats_update) stats_handle_request(vb); if (diff > 0)
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@vger.kernel.org Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- changes from v1: remove wait_event_interruptible noticed by Cornelia Huck <cornelia.huck@de.ibm.com> drivers/virtio/virtio_balloon.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)