> -----Original Message-----
> From: Ilya Maximets [mailto:i.maxim...@samsung.com]
> Sent: Wednesday, September 12, 2018 4:05 PM
> To: Zhang, Qi Z <qi.z.zh...@intel.com>; dev@dpdk.org
> Cc: Lu, Wenzhuo <wenzhuo...@intel.com>; Ananyev, Konstantin
> <konstantin.anan...@intel.com>; Laurent Hardy
> <laurent.ha...@6wind.com>; Dai, Wei <wei....@intel.com>;
> sta...@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] net/ixgbe: fix busy polling while fiber link
> update
>
> On 12.09.2018 09:49, Zhang, Qi Z wrote:
> >
> >
> >> -----Original Message-----
> >> From: Ilya Maximets [mailto:i.maxim...@samsung.com]
> >> Sent: Monday, September 10, 2018 11:09 PM
> >> To: Zhang, Qi Z <qi.z.zh...@intel.com>; dev@dpdk.org
> >> Cc: Lu, Wenzhuo <wenzhuo...@intel.com>; Ananyev, Konstantin
> >> <konstantin.anan...@intel.com>; Laurent Hardy
> >> <laurent.ha...@6wind.com>; Dai, Wei <wei....@intel.com>;
> >> sta...@dpdk.org
> >> Subject: Re: [dpdk-dev] [PATCH] net/ixgbe: fix busy polling while
> >> fiber link update
> >>
> >> On 04.09.2018 09:08, Zhang, Qi Z wrote:
> >>> Hi Ilya:
> >>>
> >>>> -----Original Message-----
> >>>> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Ilya Maximets
> >>>> Sent: Friday, August 31, 2018 8:40 PM
> >>>> To: dev@dpdk.org
> >>>> Cc: Lu, Wenzhuo <wenzhuo...@intel.com>; Ananyev, Konstantin
> >>>> <konstantin.anan...@intel.com>; Laurent Hardy
> >>>> <laurent.ha...@6wind.com>; Dai, Wei <wei....@intel.com>; Ilya
> >>>> Maximets <i.maxim...@samsung.com>; sta...@dpdk.org
> >>>> Subject: [dpdk-dev] [PATCH] net/ixgbe: fix busy polling while fiber
> >>>> link update
> >>>>
> >>>> If the multispeed fiber link is in DOWN state, ixgbe_setup_link
> >>>> could take around a second of busy polling. This is highly
> >>>> inconvenient for the case where single thread periodically checks the
> >>>> link
> statuses.
> >>>> For example, OVS main thread periodically updates the link statuses
> >>>> and hangs for a really long time busy waiting on ixgbe_setup_link()
> >>>> for a DOWN fiber ports. For case with 3 down ports it hangs for a 3
> >>>> seconds and unable to do anything including packet processing.
> >>>> Fix that by shifting that workaround to a separate thread by alarm
> >>>> handler that will try to set up link if it is DOWN.
> >>>
> >>> Does that mean we will block the interrupt thread for 3 seconds?
> >>
> >> Three times for one second. Other work could be scheduled between.
> >> IMHO, it's much better than blocking usual caller for 3 seconds.
> >>
> >>> Also, can we guarantee there will not be any race condition if we
> >>> call
> >> ixgbe_setup_link at another thread, the base code API is not assumed
> >> to be thread-safe as I know.
> >>
> >> The only user of 'ixgbe_setup_link' is 'ixgbe_dev_start', but it
> >> could be called only if device stopped. 'ixgbe_dev_stop' cancels the alarm.
> >> Race with 'link_update' avoided by 'IXGBE_FLAG_NEED_LINK_CONFIG' flag.
> >
> > I guess, it' not only about when ixgb_setup_link race with itself, but also
> when it race with other APIs.
> > Also the concern is, even in current version, we can prove there is no
> > issue,
> how can we guarantee we are safe for future base code update? It's not
> designed as thread-safe.
> > For my option, the change is risky.
>
> In current implementation interrupt handler already calls the
> 'ixgbe_dev_link_update' which subsequently calls 'ixgbe_setup_link'
> in our case if LSC interrupts enabled. So, my change makes the driver even
> safer by moving 'ixgbe_setup_link' to the same interrupt thread.
> Otherwise two threads (interrupts handler and the link status checking thread)
> could call 'ixgbe_setup_link' simultaneously.
Ok, you are right, seems the concern I have is already exist , your patch does
not introduce new issue.
So I have no objection if this will fix some issue.
But let's check if any ixgbe experts will comment.
Regards
Qi
>
> >
> > Btw, since ixgbe support LSC, it is not necessary for "single thread
> periodically checks the link statuses", right?
>
> In current implementation it will take at least 5 seconds (4 + 1) for the
> interrupt
> handler to detect DOWN link state for ixgbe multispeed fiber. This is too much
> for many real world cases.
>
> >
> >>
> >>>
> >>> Regards
> >>> Qi
> >>>
> >>>>
> >>>> Fixes: c12d22f65b13 ("net/ixgbe: ensure link status is updated")
> >>>> CC: sta...@dpdk.org
> >>>>
> >>>> Signed-off-by: Ilya Maximets <i.maxim...@samsung.com>
> >>>> ---
> >>>> drivers/net/ixgbe/ixgbe_ethdev.c | 43
> >>>> ++++++++++++++++++++++++--------
> >>>> 1 file changed, 32 insertions(+), 11 deletions(-)
> >>>>
> >>>> diff --git a/drivers/net/ixgbe/ixgbe_ethdev.c
> >>>> b/drivers/net/ixgbe/ixgbe_ethdev.c
> >>>> index 26b192737..a33b9a6e8 100644
> >>>> --- a/drivers/net/ixgbe/ixgbe_ethdev.c
> >>>> +++ b/drivers/net/ixgbe/ixgbe_ethdev.c
> >>>> @@ -221,6 +221,8 @@ static int ixgbe_dev_interrupt_action(struct
> >>>> rte_eth_dev *dev,
> >>>> struct rte_intr_handle *handle);
> >>>> static void
> >>>> ixgbe_dev_interrupt_handler(void *param); static void
> >>>> ixgbe_dev_interrupt_delayed_handler(void *param);
> >>>> +static void ixgbe_dev_setup_link_alarm_handler(void *param);
> >>>> +
> >>>> static int ixgbe_add_rar(struct rte_eth_dev *dev, struct
> >>>> ether_addr *mac_addr,
> >>>> uint32_t index, uint32_t pool); static void
> >>>> ixgbe_remove_rar(struct rte_eth_dev *dev, uint32_t index); @@
> >>>> -2791,6 +2793,8 @@ ixgbe_dev_stop(struct rte_eth_dev *dev)
> >>>>
> >>>> PMD_INIT_FUNC_TRACE();
> >>>>
> >>>> + rte_eal_alarm_cancel(ixgbe_dev_setup_link_alarm_handler, dev);
> >>>> +
> >>>> /* disable interrupts */
> >>>> ixgbe_disable_intr(hw);
> >>>>
> >>>> @@ -3969,6 +3973,25 @@ ixgbevf_check_link(struct ixgbe_hw *hw,
> >>>> ixgbe_link_speed *speed,
> >>>> return ret_val;
> >>>> }
> >>>>
> >>>> +static void
> >>>> +ixgbe_dev_setup_link_alarm_handler(void *param) {
> >>>> + struct rte_eth_dev *dev = (struct rte_eth_dev *)param;
> >>>> + struct ixgbe_hw *hw =
> >>>> IXGBE_DEV_PRIVATE_TO_HW(dev->data->dev_private);
> >>>> + struct ixgbe_interrupt *intr =
> >>>> + IXGBE_DEV_PRIVATE_TO_INTR(dev->data->dev_private);
> >>>> + u32 speed;
> >>>> + bool autoneg = false;
> >>>> +
> >>>> + speed = hw->phy.autoneg_advertised;
> >>>> + if (!speed)
> >>>> + ixgbe_get_link_capabilities(hw, &speed, &autoneg);
> >>>> +
> >>>> + ixgbe_setup_link(hw, speed, true);
> >>>> +
> >>>> + intr->flags &= ~IXGBE_FLAG_NEED_LINK_CONFIG; }
> >>>> +
> >>>> /* return 0 means link status changed, -1 means not changed */
> >>>> int ixgbe_dev_link_update_share(struct rte_eth_dev *dev, @@ -3981,9
> >>>> +4004,7 @@ ixgbe_dev_link_update_share(struct rte_eth_dev *dev,
> >>>> IXGBE_DEV_PRIVATE_TO_INTR(dev->data->dev_private);
> >>>> int link_up;
> >>>> int diag;
> >>>> - u32 speed = 0;
> >>>> int wait = 1;
> >>>> - bool autoneg = false;
> >>>>
> >>>> memset(&link, 0, sizeof(link));
> >>>> link.link_status = ETH_LINK_DOWN; @@ -3993,13 +4014,8 @@
> >>>> ixgbe_dev_link_update_share(struct
> >> rte_eth_dev
> >>>> *dev,
> >>>>
> >>>> hw->mac.get_link_status = true;
> >>>>
> >>>> - if ((intr->flags & IXGBE_FLAG_NEED_LINK_CONFIG) &&
> >>>> - ixgbe_get_media_type(hw) == ixgbe_media_type_fiber) {
> >>>> - speed = hw->phy.autoneg_advertised;
> >>>> - if (!speed)
> >>>> - ixgbe_get_link_capabilities(hw, &speed,
> >>>> &autoneg);
> >>>> - ixgbe_setup_link(hw, speed, true);
> >>>> - }
> >>>> + if (intr->flags & IXGBE_FLAG_NEED_LINK_CONFIG)
> >>>> + return rte_eth_linkstatus_set(dev, &link);
> >>>>
> >>>> /* check if it needs to wait to complete, if lsc interrupt is
> >>>> enabled */
> >>>> if (wait_to_complete == 0 || dev->data->dev_conf.intr_conf.lsc
> >>>> !=
> >>>> 0) @@
> >>>> -4017,11 +4033,14 @@ ixgbe_dev_link_update_share(struct rte_eth_dev
> >> *dev,
> >>>> }
> >>>>
> >>>> if (link_up == 0) {
> >>>> - intr->flags |= IXGBE_FLAG_NEED_LINK_CONFIG;
> >>>> + if (ixgbe_get_media_type(hw) == ixgbe_media_type_fiber)
> >>>> {
> >>>> + intr->flags |= IXGBE_FLAG_NEED_LINK_CONFIG;
> >>>> + rte_eal_alarm_set(10,
> >>>> + ixgbe_dev_setup_link_alarm_handler,
> >>>> dev);
> >>>> + }
> >>>> return rte_eth_linkstatus_set(dev, &link);
> >>>> }
> >>>>
> >>>> - intr->flags &= ~IXGBE_FLAG_NEED_LINK_CONFIG;
> >>>> link.link_status = ETH_LINK_UP;
> >>>> link.link_duplex = ETH_LINK_FULL_DUPLEX;
> >>>>
> >>>> @@ -5128,6 +5147,8 @@ ixgbevf_dev_stop(struct rte_eth_dev *dev)
> >>>>
> >>>> PMD_INIT_FUNC_TRACE();
> >>>>
> >>>> + rte_eal_alarm_cancel(ixgbe_dev_setup_link_alarm_handler, dev);
> >>>> +
> >>>> ixgbevf_intr_disable(dev);
> >>>>
> >>>> hw->adapter_stopped = 1;
> >>>> --
> >>>> 2.17.1
> >>>
