From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Beulich , Wei Liu , David Vrabel , Ian Campbell , Jason Luan , "David S. Miller" Subject: [PATCH 3.10 05/24] xen-netback: use jiffies_64 value to calculate credit timeout Date: Mon, 18 Nov 2013 10:42:15 -0800 Message-Id: <20131118184222.429032833@linuxfoundation.org> In-Reply-To: <20131118184222.017393843@linuxfoundation.org> References: <20131118184222.017393843@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wei Liu [ Upstream commit 059dfa6a93b779516321e5112db9d7621b1367ba ] 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 Signed-off-by: Wei Liu Reviewed-by: David Vrabel Cc: Ian Campbell Cc: Jason Luan Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- 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(-) --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -88,6 +88,7 @@ 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; --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -275,8 +275,7 @@ struct xenvif *xenvif_alloc(struct devic 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; --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1423,9 +1423,8 @@ 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. */ @@ -1433,8 +1432,8 @@ static bool tx_credit_exceeded(struct xe 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); } @@ -1446,6 +1445,7 @@ static bool tx_credit_exceeded(struct xe tx_credit_callback; mod_timer(&vif->credit_timeout, next_credit); + vif->credit_window_start = next_credit; return true; }