From mboxrd@z Thu Jan 1 00:00:00 1970 From: jianhai luan Subject: Re: [Xen-devel] [PATCH net] xen-netback: use jiffies_64 value to calculate credit timeout Date: Mon, 28 Oct 2013 16:36:03 +0800 Message-ID: <526E21F3.4060103@oracle.com> References: <1382872313-11675-1-git-send-email-wei.liu2@citrix.com> <526E1E97.7090804@cantab.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Ian Campbell , annie.li@oracle.com, david.vrabel@citrix.com, jbeulich@suse.com To: David Vrabel , Wei Liu , xen-devel@lists.xen.org, netdev@vger.kernel.org Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:26426 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751848Ab3J1Ihe (ORCPT ); Mon, 28 Oct 2013 04:37:34 -0400 In-Reply-To: <526E1E97.7090804@cantab.net> Sender: netdev-owner@vger.kernel.org List-ID: On 2013-10-28 16:21, David Vrabel wrote: > On 27/10/2013 11:11, 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. > Thanks. > >> Suggested-by: Jan Beulich >> Suggested-by: David Vrabel > Jan's suggestion; I just agreed with him. > >> Signed-off-by: Wei Liu >> Cc: Ian Campbell >> Cc: Jason Luan >> --- >> 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.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..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 */ > You could drop this comment as the field name makes this obvious. > >> + 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..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); >> >> /* 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; > Need to set vif->credit_window_start = now here instead of .expires. I agree Annie's suggest. add the below line; vif->credit_window_start = 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); > Need to set vif->credit_window_start = next_credit here as well. I think that we shouldn't add the above line. > > David Jason