diff options
| author | David Vrabel <david.vrabel@citrix.com> | 2014-05-16 15:26:04 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-05-17 00:27:23 +0400 |
| commit | 0d08fceb2e21c30ca3e1e462e678723f806acf18 (patch) | |
| tree | 4a890dcf919f80ffb067351bfc45cc63dab35791 | |
| parent | 202630b445d2618d94e4f099567fcee5618dab27 (diff) | |
| download | linux-0d08fceb2e21c30ca3e1e462e678723f806acf18.tar.xz | |
xen-netback: fix race between napi_complete() and interrupt handler
When the NAPI budget was not all used, xenvif_poll() would call
napi_complete() /after/ enabling the interrupt. This resulted in a
race between the napi_complete() and the napi_schedule() in the
interrupt handler. The use of local_irq_save/restore() avoided by
race iff the handler is running on the same CPU but not if it was
running on a different CPU.
Fix this properly by calling napi_complete() before reenabling
interrupts (in the xenvif_napi_schedule_or_enable_irq() call).
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | drivers/net/xen-netback/common.h | 2 | ||||
| -rw-r--r-- | drivers/net/xen-netback/interface.c | 30 | ||||
| -rw-r--r-- | drivers/net/xen-netback/netback.c | 4 |
3 files changed, 6 insertions, 30 deletions
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h index 630a3fcf65bc..0d4a285cbd7e 100644 --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -226,7 +226,7 @@ int xenvif_map_frontend_rings(struct xenvif *vif, grant_ref_t rx_ring_ref); /* Check for SKBs from frontend and schedule backend processing */ -void xenvif_check_rx_xenvif(struct xenvif *vif); +void xenvif_napi_schedule_or_enable_events(struct xenvif *vif); /* Prevent the device from generating any further traffic. */ void xenvif_carrier_off(struct xenvif *vif); diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index ef05c5c49d41..20e9defa1060 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -75,32 +75,8 @@ static int xenvif_poll(struct napi_struct *napi, int budget) work_done = xenvif_tx_action(vif, budget); if (work_done < budget) { - int more_to_do = 0; - unsigned long flags; - - /* It is necessary to disable IRQ before calling - * RING_HAS_UNCONSUMED_REQUESTS. Otherwise we might - * lose event from the frontend. - * - * Consider: - * RING_HAS_UNCONSUMED_REQUESTS - * <frontend generates event to trigger napi_schedule> - * __napi_complete - * - * This handler is still in scheduled state so the - * event has no effect at all. After __napi_complete - * this handler is descheduled and cannot get - * scheduled again. We lose event in this case and the ring - * will be completely stalled. - */ - - local_irq_save(flags); - - RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do); - if (!more_to_do) - __napi_complete(napi); - - local_irq_restore(flags); + napi_complete(napi); + xenvif_napi_schedule_or_enable_events(vif); } return work_done; @@ -194,7 +170,7 @@ static void xenvif_up(struct xenvif *vif) enable_irq(vif->tx_irq); if (vif->tx_irq != vif->rx_irq) enable_irq(vif->rx_irq); - xenvif_check_rx_xenvif(vif); + xenvif_napi_schedule_or_enable_events(vif); } static void xenvif_down(struct xenvif *vif) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 64ab1d141f1c..7367208ee8cd 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -716,7 +716,7 @@ done: notify_remote_via_irq(vif->rx_irq); } -void xenvif_check_rx_xenvif(struct xenvif *vif) +void xenvif_napi_schedule_or_enable_events(struct xenvif *vif) { int more_to_do; @@ -750,7 +750,7 @@ static void tx_credit_callback(unsigned long data) { struct xenvif *vif = (struct xenvif *)data; tx_add_credit(vif); - xenvif_check_rx_xenvif(vif); + xenvif_napi_schedule_or_enable_events(vif); } static void xenvif_tx_err(struct xenvif *vif, |