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xen-netback: use jiffies_64 value to calculate credit timeout

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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>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Liu 2013-10-28 12:07:57 +00:00 committed by David S. Miller
parent 262e827fe7
commit 059dfa6a93
3 changed files with 7 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/net/xen-netback/common.h
View File

@ -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;

3
drivers/net/xen-netback/interface.c
View File

@ -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;

10
drivers/net/xen-netback/netback.c
View File

@ -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;
}