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Date: Thu, 14 Feb 2013 16:39:07 +0000 From: Ian Campbell <Ian.Campbell@...rix.com> To: David Vrabel <david.vrabel@...rix.com>, "Christopher S. Aker" <caker@...shore.net> CC: "xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>, "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>, Jan Beulich <jbeulich@...e.com>, "Wei Liu (3P)" <wei.liu@...rix.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org> Subject: Re: [PATCH 2/2] xen-netback: cancel the credit timer when taking the vif down On Thu, 2013-02-14 at 13:18 +0000, David Vrabel wrote: > From: David Vrabel <david.vrabel@...rix.com> > > If the credit timer is left armed after calling > xen_netbk_remove_xenvif(), then it may fire and attempt to schedule > the vif which will then oops as vif->netbk == NULL. > > This may happen both in the fatal error path and during normal > disconnection from the front end. > > The sequencing during shutdown is critical to ensure that: a) > vif->netbk doesn't become unexpectedly NULL; and b) the net device/vif > is not freed. > > 1. Mark as unschedulable (netif_carrier_off()). > 2. Synchronously cancel the timer. > 3. Remove the vif from the schedule list. > 4. Remove it from it netback thread group. > 5. Wait for vif->refcnt to become 0. > > Signed-off-by: David Vrabel <david.vrabel@...rix.com> Acked-by: Ian Campbell <ian.campbell@...rix.com> Was this one also Reported-by Christopher S. Aker or was it just discovered in the process of investigating? Another stable candidate please Dave. > --- > drivers/net/xen-netback/interface.c | 3 +-- > 1 files changed, 1 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c > index b8c5193..221f426 100644 > --- a/drivers/net/xen-netback/interface.c > +++ b/drivers/net/xen-netback/interface.c > @@ -132,6 +132,7 @@ static void xenvif_up(struct xenvif *vif) > static void xenvif_down(struct xenvif *vif) > { > disable_irq(vif->irq); > + del_timer_sync(&vif->credit_timeout); > xen_netbk_deschedule_xenvif(vif); > xen_netbk_remove_xenvif(vif); > } > @@ -363,8 +364,6 @@ void xenvif_disconnect(struct xenvif *vif) > atomic_dec(&vif->refcnt); > wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0); > > - del_timer_sync(&vif->credit_timeout); > - > if (vif->irq) > unbind_from_irqhandler(vif->irq, vif); > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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