[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net] xen-netback: use jiffies_64 value to calculate credit timeout
On 2013-10-28 10:36, annie li wrote: On 2013-10-27 19:11, 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@xxxxxxxx> Suggested-by: David Vrabel <david.vrabel@xxxxxxxxxx> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx> Cc: Jason Luan <jianhai.luan@xxxxxxxxxx> --- drivers/net/xen-netback/common.h | 1 + drivers/net/xen-netback/interface.c | 4 ++-- drivers/net/xen-netback/netback.c | 13 ++++++------- 3 files changed, 9 insertions(+), 9 deletions(-)diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.hindex 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.cindex 01bb854..8c45b63 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c@@ -312,8 +312,8 @@ 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; + /* credit window is tracked in credit_window_start */ + 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.cindex f3e591c..1bc0688 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);You simply replace "credit_timeout.expires" with "vif->credit_window_start" here, and never update "vif->credit_window_start" in following code./* 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_timeout.expires = (unsigned long)now;updates credit_window_start as following, vif->credit_window_start = (unsigned long)now; both credit_window_start and credit_timeout.expires need to be updated here, vif->credit_window_start = (unsigned long)now; vif->credit_timeout.expires = (unsigned long)now; tx_add_credit(vif); }@@ -1207,7 +1206,7 @@ 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_timeout.expires is unsigned long, and this still causes original issue on 32bit system, which works well on 64bit. Or rewriting code to avoid uses of vif->credit_timeout.expires, but it is complex. My understanding here is wrong, please ignore this. Thanks Annie _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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