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From: Long Li <longli@microsoft.com>
To: Matan Azrad <matan@nvidia.com>,
	Long Li <longli@linuxonhyperv.com>,
	Matan Azrad <matan@mellanox.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, "stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [PATCH] net/vdev_netvsc: Prevent alarm lost on failed device probe
Date: Mon, 19 Oct 2020 20:38:47 +0000
Message-ID: <BN8PR21MB11555C3B59269DE97085224DCE1E0@BN8PR21MB1155.namprd21.prod.outlook.com> (raw)
In-Reply-To: <MW2PR12MB249275BEDD7010E18750F47CDF010@MW2PR12MB2492.namprd12.prod.outlook.com>

> Subject: RE: [PATCH] net/vdev_netvsc: Prevent alarm lost on failed device
> probe
> 
> 
> 
> From: Long Li
> > If a device probe fails, the alarm is canceled and will no longer work
> > for previously probed devices.
> >
> > Fix this by introducing a flag to track if alarm has been set. Because
> > it's possible that an alarm is triggered while probing is in progress
> > that may modify vdev_netvsc_ctx_list, introduce a lock to protect it.
> >
> > Cc: stable@dpdk.org
> > Signed-off-by: Long Li <longli@microsoft.com>
> > ---
> >  drivers/net/vdev_netvsc/vdev_netvsc.c | 41
> > +++++++++++++++++++++++++----------
> >  1 file changed, 30 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/net/vdev_netvsc/vdev_netvsc.c
> > b/drivers/net/vdev_netvsc/vdev_netvsc.c
> > index be8f19c..bd7e308 100644
> > --- a/drivers/net/vdev_netvsc/vdev_netvsc.c
> > +++ b/drivers/net/vdev_netvsc/vdev_netvsc.c
> > @@ -76,6 +76,11 @@ struct vdev_netvsc_ctx {
> >  /** Context list is common to all driver instances. */  static
> > LIST_HEAD(,
> > vdev_netvsc_ctx) vdev_netvsc_ctx_list =
> >         LIST_HEAD_INITIALIZER(vdev_netvsc_ctx_list);
> > +/* Lock to protect concurrent accesses to vdev_netvsc_ctx_list */
> > +static rte_rwlock_t vdev_netvsc_ctx_list_lock;
> > +
> > +/* Flag to track if alarm has been set */ static int
> > +vdev_netvsc_alarm_set;
> >
> >  /** Number of entries in context list. */  static unsigned int
> > vdev_netvsc_ctx_count; @@ -454,19 +459,26 @@ static LIST_HEAD(,
> > vdev_netvsc_ctx) vdev_netvsc_ctx_list =
> >         struct vdev_netvsc_ctx *ctx;
> >         int ret;
> >
> > +       rte_rwlock_write_lock(&vdev_netvsc_ctx_list_lock);
> >         LIST_FOREACH(ctx, &vdev_netvsc_ctx_list, entry) {
> >                 ret = vdev_netvsc_foreach_iface(vdev_netvsc_device_probe, 0,
> >                       ctx);
> >                 if (ret < 0)
> >                         break;
> >         }
> > -       if (!vdev_netvsc_ctx_count)
> > +       rte_rwlock_write_unlock(&vdev_netvsc_ctx_list_lock);
> > +
> > +       if (!vdev_netvsc_ctx_count) {
> > +               vdev_netvsc_alarm_set = 0;
> >                 return;
> > +       }
> > +
> >         ret = rte_eal_alarm_set(VDEV_NETVSC_PROBE_MS * 1000,
> >                                 vdev_netvsc_alarm, NULL);
> >         if (ret < 0) {
> >                 DRV_LOG(ERR, "unable to reschedule alarm callback: %s",
> >                         rte_strerror(-ret));
> > +               vdev_netvsc_alarm_set = 0;
> >         }
> >  }
> >
> > @@ -698,34 +710,41 @@ static LIST_HEAD(, vdev_netvsc_ctx)
> > vdev_netvsc_ctx_list =
> >                         " device.");
> >                 goto error;
> >         }
> > -       rte_eal_alarm_cancel(vdev_netvsc_alarm, NULL);
> > +
> > +       rte_rwlock_write_lock(&vdev_netvsc_ctx_list_lock);
> >         /* Gather interfaces. */
> >         ret = vdev_netvsc_foreach_iface(vdev_netvsc_netvsc_probe, 1,
> name,
> >                                         kvargs, specified, &matched);
> >         if (ret < 0)
> > -               goto error;
> > +               goto error_unlock;
> >         if (specified && matched < specified) {
> >                 if (!force) {
> >                         DRV_LOG(ERR, "Cannot find the specified netvsc device");
> > -                       goto error;
> > +                       goto error_unlock;
> >                 }
> >                 /* Try to force probing on non-netvsc specified device. */
> >                 if (vdev_netvsc_foreach_iface(vdev_netvsc_netvsc_probe, 0,
> name,
> >                                               kvargs, specified, &matched) < 0)
> > -                       goto error;
> > +                       goto error_unlock;
> >                 if (matched < specified) {
> >                         DRV_LOG(ERR, "Cannot find the specified device");
> > -                       goto error;
> > +                       goto error_unlock;
> >                 }
> >                 DRV_LOG(WARNING, "non-netvsc device was probed as netvsc");
> >         }
> > -       ret = rte_eal_alarm_set(VDEV_NETVSC_PROBE_MS * 1000,
> > +       if (!vdev_netvsc_alarm_set) {
> > +               ret = rte_eal_alarm_set(VDEV_NETVSC_PROBE_MS * 1000,
> >                                 vdev_netvsc_alarm, NULL);
> > -       if (ret < 0) {
> > -               DRV_LOG(ERR, "unable to schedule alarm callback: %s",
> > -                       rte_strerror(-ret));
> > -               goto error;
> > +               if (ret < 0)
> > +                       DRV_LOG(ERR, "unable to schedule alarm callback: %s",
> > +                               rte_strerror(-ret));
> > +               else
> > +                       vdev_netvsc_alarm_set = 1;
> >         }
> > +
> > +error_unlock:
> > +       rte_rwlock_write_unlock(&vdev_netvsc_ctx_list_lock);
> > +
> >  error:
> >         if (kvargs)
> >                 rte_kvargs_free(kvargs);
> > --
> 
> Hi
> 
> Nice direction.
> 
> As I understand from your patch it looks like you want to add support for the
> vdev_netvsc driver itself to be hot-plug aware - so it can be probed\removed
> in run-time (even after EAL initialization).
> So I think the title and commit log should be converted to this:
> net/vdev_netvsc: support driver instance hot-plug ...

Hi Matan,

Actually I was not trying to add support for hot-plug (although it made half way there).

The problem I'm trying to solve is on a system with multiple vdev_netvsc interfaces. For example, if the system has eth1, eth2 .. eth10. What if the probing on eth1 to eth9 succeed, but on eth10 fails? Current behavior is that we can still have DPDK run on eth1 to eth9, but without any alarms. Because the alarm is canceled while trying to probing eth10. Then once eth1 to eth9 lost VF, they won't get VF back because we don't have any alarms.

Long

> 
> More things:
> Look on convention of the file - blank line only after variables declarations
> inside the blocks.
> 
> Need to adjust also vdev_netvsc_vdev_remove to the feature.
> 
> Matan

  reply	other threads:[~2020-10-19 20:38 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-15 19:33 Long Li
2020-10-18  7:31 ` Matan Azrad
2020-10-19 20:38   ` Long Li [this message]
2020-10-20  5:50     ` Matan Azrad
2020-10-20 21:39       ` Long Li

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