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Message-ID: <Zsdyz3WqrYCz98QL@lzaremba-mobl.ger.corp.intel.com>
Date: Thu, 22 Aug 2024 19:18:07 +0200
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, Tony Nguyen
<anthony.l.nguyen@...el.com>, "David S. Miller" <davem@...emloft.net>, "Jacob
Keller" <jacob.e.keller@...el.com>, Eric Dumazet <edumazet@...gle.com>, Jakub
Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper
Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>,
<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<bpf@...r.kernel.org>, <magnus.karlsson@...el.com>, Michal Kubiak
<michal.kubiak@...el.com>, Wojciech Drewek <wojciech.drewek@...el.com>,
Amritha Nambiar <amritha.nambiar@...el.com>, Chandan Kumar Rout
<chandanx.rout@...el.com>
Subject: Re: [PATCH iwl-net v3 4/6] ice: check ICE_VSI_DOWN under rtnl_lock
when preparing for reset
On Thu, Aug 22, 2024 at 04:42:44PM +0200, Maciej Fijalkowski wrote:
> On Thu, Aug 22, 2024 at 02:56:50PM +0200, Larysa Zaremba wrote:
> > On Thu, Aug 22, 2024 at 01:34:33PM +0200, Maciej Fijalkowski wrote:
> > > On Mon, Aug 19, 2024 at 12:05:41PM +0200, Larysa Zaremba wrote:
> > > > Consider the following scenario:
> > > >
> > > > .ndo_bpf() | ice_prepare_for_reset() |
> > > > ________________________|_______________________________________|
> > > > rtnl_lock() | |
> > > > ice_down() | |
> > > > | test_bit(ICE_VSI_DOWN) - true |
> > > > | ice_dis_vsi() returns |
> > > > ice_up() | |
> > > > | proceeds to rebuild a running VSI |
> > > >
> > > > .ndo_bpf() is not the only rtnl-locked callback that toggles the interface
> > > > to apply new configuration. Another example is .set_channels().
> > > >
> > > > To avoid the race condition above, act only after reading ICE_VSI_DOWN
> > > > under rtnl_lock.
> > > >
> > > > Fixes: 0f9d5027a749 ("ice: Refactor VSI allocation, deletion and rebuild flow")
> > > > Reviewed-by: Wojciech Drewek <wojciech.drewek@...el.com>
> > > > Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
> > > > Tested-by: Chandan Kumar Rout <chandanx.rout@...el.com>
> > > > Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
> > > > ---
> > > > drivers/net/ethernet/intel/ice/ice_lib.c | 12 ++++++------
> > > > 1 file changed, 6 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> > > > index b72338974a60..94029e446b99 100644
> > > > --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> > > > +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> > > > @@ -2665,8 +2665,7 @@ int ice_ena_vsi(struct ice_vsi *vsi, bool locked)
> > > > */
> > > > void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
> > > > {
> > > > - if (test_bit(ICE_VSI_DOWN, vsi->state))
> > > > - return;
> > > > + bool already_down = test_bit(ICE_VSI_DOWN, vsi->state);
> > > >
> > > > set_bit(ICE_VSI_NEEDS_RESTART, vsi->state);
> > > >
> > > > @@ -2674,15 +2673,16 @@ void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
> > > > if (netif_running(vsi->netdev)) {
> > > > if (!locked)
> > > > rtnl_lock();
> > > > -
> > > > - ice_vsi_close(vsi);
> > > > + already_down = test_bit(ICE_VSI_DOWN, vsi->state);
> > > > + if (!already_down)
> > > > + ice_vsi_close(vsi);
> > >
> > > ehh sorry for being sloppy reviewer. we still are testing ICE_VSI_DOWN in
> > > ice_vsi_close(). wouldn't all of this be cleaner if we would bail out of
> > > the called function when bit was already set?
> > >
> >
> > I am not sure I see the possibility to rewrite this as you suggest, we cannot
> > bail out for the netif_running() case due to needing to unlock after
> > ice_vsi_close() finishes. This leaves bailing out in case of CTRL VSI and
> > non-running PF, which we could do, but it would require a lengthy if condition,
> > which is not that much better than nested code, IMO.
>
> Hmm. I meant to move bit checking onto ice_vsi_close() only, so you would
> bail out of it in case bit has already been set.
>
> overall, ice_dis_vsi() is a very cumbersome way of calling ice_vsi_close()
> :(
>
> I guess we can progress with what you have but i'd like to brainstorm
> later about some simplification around it.
>
> I prototyped something but not tested that, just to maybe spark a
> discussion. Feels easier to read and swallow in the end. Not sure if
> functionality is kept:)
>
Ok, now I get it.
Yes, this is something worth considering for a -next patch. Opting out of
closing the VSI based on a down state seems not very nice though :/
I am not even sure if such approach is correct in ice_dis_vsi or is it just
some ancient atrifact.
Seems like it needs some VSI state changes analysis.
> From 706289d5c37c41cd3021997e0d5e64d7496e5536 Mon Sep 17 00:00:00 2001
> From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Date: Thu, 22 Aug 2024 16:33:37 +0200
> Subject: [PATCH] ice: simplify ice_dis_vsi()
>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---
> drivers/net/ethernet/intel/ice/ice_lib.c | 46 +++++++++++++-----------
> 1 file changed, 26 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> index f559e60992fa..8ccdda69a1d4 100644
> --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> @@ -2625,14 +2625,34 @@ void ice_vsi_free_rx_rings(struct ice_vsi *vsi)
> */
> void ice_vsi_close(struct ice_vsi *vsi)
> {
> - if (!test_and_set_bit(ICE_VSI_DOWN, vsi->state))
> - ice_down(vsi);
> + if (test_bit(ICE_VSI_DOWN, vsi->state))
> + return;
> +
> + set_bit(ICE_VSI_DOWN, vsi->state);
>
> + ice_down(vsi);
> ice_vsi_free_irq(vsi);
> ice_vsi_free_tx_rings(vsi);
> ice_vsi_free_rx_rings(vsi);
> }
>
> +/**
> + * __ice_vsi_close - variant of shutting down a VSI that takes care of
> + * rtnl_lock
> + * @vsi: the VSI being shut down
> + * @take_lock: to lock or not to lock
> + */
> +static void __ice_vsi_close(struct ice_vsi *vsi, bool take_lock)
> +{
> + if (take_lock)
> + rtnl_lock();
> +
> + ice_vsi_close(vsi);
> +
> + if (take_lock)
> + rtnl_unlock();
> +}
> +
> /**
> * ice_ena_vsi - resume a VSI
> * @vsi: the VSI being resume
> @@ -2671,26 +2691,12 @@ int ice_ena_vsi(struct ice_vsi *vsi, bool locked)
> */
> void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
> {
> - if (test_bit(ICE_VSI_DOWN, vsi->state))
> - return;
> -
> set_bit(ICE_VSI_NEEDS_RESTART, vsi->state);
>
> - if (vsi->type == ICE_VSI_PF && vsi->netdev) {
> - if (netif_running(vsi->netdev)) {
> - if (!locked)
> - rtnl_lock();
> -
> - ice_vsi_close(vsi);
> -
> - if (!locked)
> - rtnl_unlock();
> - } else {
> - ice_vsi_close(vsi);
> - }
> - } else if (vsi->type == ICE_VSI_CTRL) {
> - ice_vsi_close(vsi);
> - }
> + if (vsi->type == ICE_VSI_PF && vsi->netdev)
> + __ice_vsi_close(vsi, !locked && netif_running(vsi->netdev));
> + else if (vsi->type == ICE_VSI_CTRL)
> + __ice_vsi_close(vsi, false);
> }
>
> /**
> --
> 2.34.1
>
>
>
> >
> > > >
> > > > if (!locked)
> > > > rtnl_unlock();
> > > > - } else {
> > > > + } else if (!already_down) {
> > > > ice_vsi_close(vsi);
> > > > }
> > > > - } else if (vsi->type == ICE_VSI_CTRL) {
> > > > + } else if (vsi->type == ICE_VSI_CTRL && !already_down) {
> > > > ice_vsi_close(vsi);
> > > > }
> > > > }
> > > > --
> > > > 2.43.0
> > > >
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