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Message-ID: <ZsdOZM9VkSpCouJO@boxer>
Date: Thu, 22 Aug 2024 16:42:44 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Larysa Zaremba <larysa.zaremba@...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 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:)
>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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