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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
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10
drivers/net/xen-netback/netback.c
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@@ -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;
}