Re: [PATCH v2] virtio-balloon: do not call blocking ops when !TASK_RUNNING
Thomas Huth th...@linux.vnet.ibm.com writes: On Wed, 25 Feb 2015 16:11:27 +0100 Cornelia Huck cornelia.h...@de.ibm.com wrote: On Wed, 25 Feb 2015 15:36:02 +0100 Michael S. Tsirkin m...@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: sta...@vger.kernel.org Reported-by: Thomas Huth th...@linux.vnet.ibm.com Signed-off-by: Michael S. Tsirkin m...@redhat.com --- changes from v1: remove wait_event_interruptible noticed by Cornelia Huck cornelia.h...@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.h...@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 th...@linux.vnet.ibm.com Applied. Thanks, Rusty. ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
[PATCH v2] virtio-balloon: do not call blocking ops when !TASK_RUNNING
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: sta...@vger.kernel.org Reported-by: Thomas Huth th...@linux.vnet.ibm.com Signed-off-by: Michael S. Tsirkin m...@redhat.com --- changes from v1: remove wait_event_interruptible noticed by Cornelia Huck cornelia.h...@de.ibm.com drivers/virtio/virtio_balloon.c | 19 ++- 1 file changed, 14 insertions(+), 5 deletions(-) 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) -- MST ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH v2] virtio-balloon: do not call blocking ops when !TASK_RUNNING
On Wed, 25 Feb 2015 16:11:27 +0100 Cornelia Huck cornelia.h...@de.ibm.com wrote: On Wed, 25 Feb 2015 15:36:02 +0100 Michael S. Tsirkin m...@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: sta...@vger.kernel.org Reported-by: Thomas Huth th...@linux.vnet.ibm.com Signed-off-by: Michael S. Tsirkin m...@redhat.com --- changes from v1: remove wait_event_interruptible noticed by Cornelia Huck cornelia.h...@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.h...@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 th...@linux.vnet.ibm.com ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization