Wei Liu
2013-Oct-28 12:07 UTC
[PATCH net V3] xen-netback: use jiffies_64 value to calculate credit timeout
time_after_eq() only works if the delta is < MAX_ULONG/2.
For a 32bit Dom0, if netfront sends packets at a very low rate, the time
between subsequent calls to tx_credit_exceeded() may exceed MAX_ULONG/2
and the test for timer_after_eq() will be incorrect. Credit will not be
replenished and the guest may become unable to send packets (e.g., if
prior to the long gap, all credit was exhausted).
Use jiffies_64 variant to mitigate this problem for 32bit Dom0.
Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Jason Luan <jianhai.luan@oracle.com>
---
drivers/net/xen-netback/common.h | 1 +
drivers/net/xen-netback/interface.c | 3 +--
drivers/net/xen-netback/netback.c | 10 +++++-----
3 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 5715318..400fea1 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -163,6 +163,7 @@ struct xenvif {
unsigned long credit_usec;
unsigned long remaining_credit;
struct timer_list credit_timeout;
+ u64 credit_window_start;
/* Statistics */
unsigned long rx_gso_checksum_fixup;
diff --git a/drivers/net/xen-netback/interface.c
b/drivers/net/xen-netback/interface.c
index 01bb854..459935a 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -312,8 +312,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t
domid,
vif->credit_bytes = vif->remaining_credit = ~0UL;
vif->credit_usec = 0UL;
init_timer(&vif->credit_timeout);
- /* Initialize ''expires'' now: it''s used to track the
credit window. */
- vif->credit_timeout.expires = jiffies;
+ vif->credit_window_start = get_jiffies_64();
dev->netdev_ops = &xenvif_netdev_ops;
dev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO;
diff --git a/drivers/net/xen-netback/netback.c
b/drivers/net/xen-netback/netback.c
index f3e591c..900da4b 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1185,9 +1185,8 @@ out:
static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
{
- unsigned long now = jiffies;
- unsigned long next_credit - vif->credit_timeout.expires +
+ u64 now = get_jiffies_64();
+ u64 next_credit = vif->credit_window_start +
msecs_to_jiffies(vif->credit_usec / 1000);
/* Timer could already be pending in rare cases. */
@@ -1195,8 +1194,8 @@ static bool tx_credit_exceeded(struct xenvif *vif,
unsigned size)
return true;
/* Passed the point where we can replenish credit? */
- if (time_after_eq(now, next_credit)) {
- vif->credit_timeout.expires = now;
+ if (time_after_eq64(now, next_credit)) {
+ vif->credit_window_start = now;
tx_add_credit(vif);
}
@@ -1208,6 +1207,7 @@ static bool tx_credit_exceeded(struct xenvif *vif,
unsigned size)
tx_credit_callback;
mod_timer(&vif->credit_timeout,
next_credit);
+ vif->credit_window_start = next_credit;
return true;
}
--
1.7.10.4
annie li
2013-Oct-29 02:39 UTC
Re: [PATCH net V3] xen-netback: use jiffies_64 value to calculate credit timeout
On 2013-10-28 20:07, Wei Liu wrote:> time_after_eq() only works if the delta is < MAX_ULONG/2. > > For a 32bit Dom0, if netfront sends packets at a very low rate, the time > between subsequent calls to tx_credit_exceeded() may exceed MAX_ULONG/2 > and the test for timer_after_eq() will be incorrect. Credit will not be > replenished and the guest may become unable to send packets (e.g., if > prior to the long gap, all credit was exhausted). > > Use jiffies_64 variant to mitigate this problem for 32bit Dom0. > > Suggested-by: Jan Beulich <jbeulich@suse.com> > Signed-off-by: Wei Liu <wei.liu2@citrix.com> > Reviewed-by: David Vrabel <david.vrabel@citrix.com> > Cc: Ian Campbell <ian.campbell@citrix.com> > Cc: Jason Luan <jianhai.luan@oracle.com> > --- > drivers/net/xen-netback/common.h | 1 + > drivers/net/xen-netback/interface.c | 3 +-- > drivers/net/xen-netback/netback.c | 10 +++++----- > 3 files changed, 7 insertions(+), 7 deletions(-) > > diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h > index 5715318..400fea1 100644 > --- a/drivers/net/xen-netback/common.h > +++ b/drivers/net/xen-netback/common.h > @@ -163,6 +163,7 @@ struct xenvif { > unsigned long credit_usec; > unsigned long remaining_credit; > struct timer_list credit_timeout; > + u64 credit_window_start; > > /* Statistics */ > unsigned long rx_gso_checksum_fixup; > diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c > index 01bb854..459935a 100644 > --- a/drivers/net/xen-netback/interface.c > +++ b/drivers/net/xen-netback/interface.c > @@ -312,8 +312,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid, > vif->credit_bytes = vif->remaining_credit = ~0UL; > vif->credit_usec = 0UL; > init_timer(&vif->credit_timeout); > - /* Initialize ''expires'' now: it''s used to track the credit window. */ > - vif->credit_timeout.expires = jiffies; > + vif->credit_window_start = get_jiffies_64(); > > dev->netdev_ops = &xenvif_netdev_ops; > dev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO; > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > index f3e591c..900da4b 100644 > --- a/drivers/net/xen-netback/netback.c > +++ b/drivers/net/xen-netback/netback.c > @@ -1185,9 +1185,8 @@ out: > > static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) > { > - unsigned long now = jiffies; > - unsigned long next_credit > - vif->credit_timeout.expires + > + u64 now = get_jiffies_64(); > + u64 next_credit = vif->credit_window_start + > msecs_to_jiffies(vif->credit_usec / 1000); > > /* Timer could already be pending in rare cases. */ > @@ -1195,8 +1194,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) > return true; > > /* Passed the point where we can replenish credit? */ > - if (time_after_eq(now, next_credit)) { > - vif->credit_timeout.expires = now; > + if (time_after_eq64(now, next_credit)) { > + vif->credit_window_start = now; > tx_add_credit(vif); > } > > @@ -1208,6 +1207,7 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) > tx_credit_callback; > mod_timer(&vif->credit_timeout, > next_credit); > + vif->credit_window_start = next_credit; > > return true; > }This patch looks good, thanks Wei. Thanks Annie
David Miller
2013-Oct-29 04:25 UTC
Re: [PATCH net V3] xen-netback: use jiffies_64 value to calculate credit timeout
From: Wei Liu <wei.liu2@citrix.com> Date: Mon, 28 Oct 2013 12:07:57 +0000> time_after_eq() only works if the delta is < MAX_ULONG/2. > > For a 32bit Dom0, if netfront sends packets at a very low rate, the time > between subsequent calls to tx_credit_exceeded() may exceed MAX_ULONG/2 > and the test for timer_after_eq() will be incorrect. Credit will not be > replenished and the guest may become unable to send packets (e.g., if > prior to the long gap, all credit was exhausted). > > Use jiffies_64 variant to mitigate this problem for 32bit Dom0. > > Suggested-by: Jan Beulich <jbeulich@suse.com> > Signed-off-by: Wei Liu <wei.liu2@citrix.com> > Reviewed-by: David Vrabel <david.vrabel@citrix.com>Applied and queued up for -stable, thanks.