aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/net
diff options
context:
space:
mode:
authorDavid Vrabel <david.vrabel@citrix.com>2014-05-16 12:26:04 +0100
committerDavid S. Miller <davem@davemloft.net>2014-05-16 16:27:23 -0400
commit0d08fceb2e21c30ca3e1e462e678723f806acf18 (patch)
tree4a890dcf919f80ffb067351bfc45cc63dab35791 /drivers/net
parentMerge branch 'for-davem' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless (diff)
downloadlinux-dev-0d08fceb2e21c30ca3e1e462e678723f806acf18.tar.xz
linux-dev-0d08fceb2e21c30ca3e1e462e678723f806acf18.zip
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>
Diffstat (limited to 'drivers/net')
-rw-r--r--drivers/net/xen-netback/common.h2
-rw-r--r--drivers/net/xen-netback/interface.c30
-rw-r--r--drivers/net/xen-netback/netback.c4
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,