Re: [[PATCH stable <3.12]] xen-netback: fix refcnt unbalance for 3.11 and earlier versions
From: Ian Campbell <hidden>
Date: 2013-11-28 13:08:53
On Thu, 2013-11-28 at 12:48 +0000, Wei Liu wrote:
With the introduction of "xen-netback: Don't destroy the netdev until the vif is shut down" (upstream commit id 279f438e36), vif disconnect and free are separated. However in the backported verion reference counting code was not correctly modified, and the reset of vif->tx_irq was lost. If frontend goes through vif life cycle more than once the reference counting is skewed. This patch adds back the missing tx_irq reset line. It also moves several lines of the reference counting code to vif_free, so the moved code corresponds to the counterpart in vif_alloc, thus the reference counting is balanced.
Is this a requirement of the bugfix or just to make reasoning about things easier?
3.12 and onward versions are not affected by this bug, because reference counting code was removed due to the introduction of 1:1 model. This pacth should be backported to all stable verions which are lower than 3.12 and have 279f438e36. Reported-and-tested-by: Tomasz Wroblewski <redacted> Signed-off-by: Wei Liu <redacted>
Acked-by: Ian Campbell <redacted>
quoted hunk ↗ jump to hunk
Cc: Konrad Wilk <redacted> Cc: David Vrabel <redacted> --- drivers/net/xen-netback/interface.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index d28324a..342d4e5 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c@@ -418,9 +418,6 @@ void xenvif_disconnect(struct xenvif *vif) if (netif_carrier_ok(vif->dev)) xenvif_carrier_off(vif); - atomic_dec(&vif->refcnt); - wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0); - if (vif->tx_irq) { if (vif->tx_irq == vif->rx_irq) unbind_from_irqhandler(vif->tx_irq, vif);@@ -428,6 +425,7 @@ void xenvif_disconnect(struct xenvif *vif) unbind_from_irqhandler(vif->tx_irq, vif); unbind_from_irqhandler(vif->rx_irq, vif); } + vif->tx_irq = 0; } xen_netbk_unmap_frontend_rings(vif);@@ -435,6 +433,9 @@ void xenvif_disconnect(struct xenvif *vif) void xenvif_free(struct xenvif *vif) { + atomic_dec(&vif->refcnt); + wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0); + unregister_netdev(vif->dev); free_netdev(vif->dev);