* [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
@ 2013-10-28 11:35 Wei Liu
2013-10-28 11:49 ` Jan Beulich
` (3 more replies)
0 siblings, 4 replies; 7+ messages in thread
From: Wei Liu @ 2013-10-28 11:35 UTC (permalink / raw)
To: xen-devel, netdev
Cc: david.vrabel, jbeulich, annie.li, Wei Liu, Ian Campbell, Jason Luan
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>
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 | 14 +++++++-------
3 files changed, 9 insertions(+), 9 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..8644aca 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1185,18 +1185,17 @@ out:
static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
{
- unsigned long now = jiffies;
- unsigned long next_credit =
- vif->credit_timeout.expires +
- msecs_to_jiffies(vif->credit_usec / 1000);
+ u64 now = get_jiffies_64();
+ u64 next_credit = vif->credit_window_start +
+ (u64)msecs_to_jiffies(vif->credit_usec / 1000);
/* Timer could already be pending in rare cases. */
if (timer_pending(&vif->credit_timeout))
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);
}
@@ -1207,7 +1206,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
vif->credit_timeout.function =
tx_credit_callback;
mod_timer(&vif->credit_timeout,
- next_credit);
+ (unsigned long)next_credit);
+ vif->credit_window_start = next_credit;
return true;
}
--
1.7.10.4
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
2013-10-28 11:35 [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout Wei Liu
2013-10-28 11:49 ` Jan Beulich
@ 2013-10-28 11:49 ` Jan Beulich
2013-10-28 12:01 ` Wei Liu
2013-10-28 12:01 ` Wei Liu
2013-10-28 11:53 ` [Xen-devel] " David Vrabel
2013-10-28 11:53 ` David Vrabel
3 siblings, 2 replies; 7+ messages in thread
From: Jan Beulich @ 2013-10-28 11:49 UTC (permalink / raw)
To: Wei Liu
Cc: david.vrabel, Ian Campbell, xen-devel, annie.li, Jason Luan, netdev
>>> On 28.10.13 at 12:35, Wei Liu <wei.liu2@citrix.com> wrote:
Two formal things:
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1185,18 +1185,17 @@ out:
>
> static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> {
> - unsigned long now = jiffies;
> - unsigned long next_credit =
> - vif->credit_timeout.expires +
> - msecs_to_jiffies(vif->credit_usec / 1000);
> + u64 now = get_jiffies_64();
> + u64 next_credit = vif->credit_window_start +
> + (u64)msecs_to_jiffies(vif->credit_usec / 1000);
The cast to u64 seems pointless here.
> @@ -1207,7 +1206,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> vif->credit_timeout.function =
> tx_credit_callback;
> mod_timer(&vif->credit_timeout,
> - next_credit);
> + (unsigned long)next_credit);
And the cast here seems pointless too (gcc doesn't warn about
truncations).
Jan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
2013-10-28 11:35 [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout Wei Liu
@ 2013-10-28 11:49 ` Jan Beulich
2013-10-28 11:49 ` Jan Beulich
` (2 subsequent siblings)
3 siblings, 0 replies; 7+ messages in thread
From: Jan Beulich @ 2013-10-28 11:49 UTC (permalink / raw)
To: Wei Liu
Cc: Ian Campbell, netdev, annie.li, david.vrabel, xen-devel, Jason Luan
>>> On 28.10.13 at 12:35, Wei Liu <wei.liu2@citrix.com> wrote:
Two formal things:
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1185,18 +1185,17 @@ out:
>
> static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> {
> - unsigned long now = jiffies;
> - unsigned long next_credit =
> - vif->credit_timeout.expires +
> - msecs_to_jiffies(vif->credit_usec / 1000);
> + u64 now = get_jiffies_64();
> + u64 next_credit = vif->credit_window_start +
> + (u64)msecs_to_jiffies(vif->credit_usec / 1000);
The cast to u64 seems pointless here.
> @@ -1207,7 +1206,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> vif->credit_timeout.function =
> tx_credit_callback;
> mod_timer(&vif->credit_timeout,
> - next_credit);
> + (unsigned long)next_credit);
And the cast here seems pointless too (gcc doesn't warn about
truncations).
Jan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Xen-devel] [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
2013-10-28 11:35 [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout Wei Liu
2013-10-28 11:49 ` Jan Beulich
2013-10-28 11:49 ` Jan Beulich
@ 2013-10-28 11:53 ` David Vrabel
2013-10-28 11:53 ` David Vrabel
3 siblings, 0 replies; 7+ messages in thread
From: David Vrabel @ 2013-10-28 11:53 UTC (permalink / raw)
To: Wei Liu, xen-devel, netdev
Cc: Ian Campbell, annie.li, david.vrabel, jbeulich, Jason Luan
On 28/10/2013 11:35, 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.
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
David
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
2013-10-28 11:35 [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout Wei Liu
` (2 preceding siblings ...)
2013-10-28 11:53 ` [Xen-devel] " David Vrabel
@ 2013-10-28 11:53 ` David Vrabel
3 siblings, 0 replies; 7+ messages in thread
From: David Vrabel @ 2013-10-28 11:53 UTC (permalink / raw)
To: Wei Liu, xen-devel, netdev
Cc: Jason Luan, annie.li, Ian Campbell, jbeulich, david.vrabel
On 28/10/2013 11:35, 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.
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
David
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
2013-10-28 11:49 ` Jan Beulich
2013-10-28 12:01 ` Wei Liu
@ 2013-10-28 12:01 ` Wei Liu
1 sibling, 0 replies; 7+ messages in thread
From: Wei Liu @ 2013-10-28 12:01 UTC (permalink / raw)
To: Jan Beulich
Cc: Wei Liu, david.vrabel, Ian Campbell, xen-devel, annie.li,
Jason Luan, netdev
On Mon, Oct 28, 2013 at 11:49:55AM +0000, Jan Beulich wrote:
> >>> On 28.10.13 at 12:35, Wei Liu <wei.liu2@citrix.com> wrote:
>
> Two formal things:
>
> > --- a/drivers/net/xen-netback/netback.c
> > +++ b/drivers/net/xen-netback/netback.c
> > @@ -1185,18 +1185,17 @@ out:
> >
> > static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> > {
> > - unsigned long now = jiffies;
> > - unsigned long next_credit =
> > - vif->credit_timeout.expires +
> > - msecs_to_jiffies(vif->credit_usec / 1000);
> > + u64 now = get_jiffies_64();
> > + u64 next_credit = vif->credit_window_start +
> > + (u64)msecs_to_jiffies(vif->credit_usec / 1000);
>
> The cast to u64 seems pointless here.
>
> > @@ -1207,7 +1206,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> > vif->credit_timeout.function =
> > tx_credit_callback;
> > mod_timer(&vif->credit_timeout,
> > - next_credit);
> > + (unsigned long)next_credit);
>
> And the cast here seems pointless too (gcc doesn't warn about
> truncations).
>
Will fix these, thanks.
Wei.
> Jan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout
2013-10-28 11:49 ` Jan Beulich
@ 2013-10-28 12:01 ` Wei Liu
2013-10-28 12:01 ` Wei Liu
1 sibling, 0 replies; 7+ messages in thread
From: Wei Liu @ 2013-10-28 12:01 UTC (permalink / raw)
To: Jan Beulich
Cc: Wei Liu, Ian Campbell, netdev, annie.li, david.vrabel, xen-devel,
Jason Luan
On Mon, Oct 28, 2013 at 11:49:55AM +0000, Jan Beulich wrote:
> >>> On 28.10.13 at 12:35, Wei Liu <wei.liu2@citrix.com> wrote:
>
> Two formal things:
>
> > --- a/drivers/net/xen-netback/netback.c
> > +++ b/drivers/net/xen-netback/netback.c
> > @@ -1185,18 +1185,17 @@ out:
> >
> > static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> > {
> > - unsigned long now = jiffies;
> > - unsigned long next_credit =
> > - vif->credit_timeout.expires +
> > - msecs_to_jiffies(vif->credit_usec / 1000);
> > + u64 now = get_jiffies_64();
> > + u64 next_credit = vif->credit_window_start +
> > + (u64)msecs_to_jiffies(vif->credit_usec / 1000);
>
> The cast to u64 seems pointless here.
>
> > @@ -1207,7 +1206,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
> > vif->credit_timeout.function =
> > tx_credit_callback;
> > mod_timer(&vif->credit_timeout,
> > - next_credit);
> > + (unsigned long)next_credit);
>
> And the cast here seems pointless too (gcc doesn't warn about
> truncations).
>
Will fix these, thanks.
Wei.
> Jan
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2013-10-28 12:01 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-10-28 11:35 [PATCH net V2] xen-netback: use jiffies_64 value to calculate credit timeout Wei Liu
2013-10-28 11:49 ` Jan Beulich
2013-10-28 11:49 ` Jan Beulich
2013-10-28 12:01 ` Wei Liu
2013-10-28 12:01 ` Wei Liu
2013-10-28 11:53 ` [Xen-devel] " David Vrabel
2013-10-28 11:53 ` David Vrabel
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