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Message-Id: <20210615145455.564037-9-toke@redhat.com>
Date: Tue, 15 Jun 2021 16:54:47 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: bpf@...r.kernel.org, netdev@...r.kernel.org
Cc: Martin KaFai Lau <kafai@...com>,
Hangbin Liu <liuhangbin@...il.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Magnus Karlsson <magnus.karlsson@...il.com>,
"Paul E . McKenney" <paulmck@...nel.org>,
Jakub Kicinski <kuba@...nel.org>,
Toke Høiland-Jørgensen <toke@...hat.com>,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
intel-wired-lan@...ts.osuosl.org
Subject: [PATCH bpf-next v2 08/16] net: intel: remove rcu_read_lock() around XDP program invocation
The Intel drivers all have rcu_read_lock()/rcu_read_unlock() pairs around
XDP program invocations. However, the actual lifetime of the objects
referred by the XDP program invocation is longer, all the way through to
the call to xdp_do_flush(), making the scope of the rcu_read_lock() too
small. This turns out to be harmless because it all happens in a single
NAPI poll cycle (and thus under local_bh_disable()), but it makes the
rcu_read_lock() misleading.
Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. With the addition of RCU annotations to the XDP_REDIRECT map
types that take bh execution into account, lockdep even understands this to
be safe, so there's really no reason to keep it around.
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org
Tested-by: Jesper Dangaard Brouer <brouer@...hat.com> # i40e
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
drivers/net/ethernet/intel/i40e/i40e_txrx.c | 5 +++--
drivers/net/ethernet/intel/i40e/i40e_xsk.c | 11 +++++------
drivers/net/ethernet/intel/ice/ice_txrx.c | 6 +-----
drivers/net/ethernet/intel/ice/ice_xsk.c | 6 +-----
drivers/net/ethernet/intel/igb/igb_main.c | 5 +++--
drivers/net/ethernet/intel/igc/igc_main.c | 10 +++++-----
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 5 +++--
drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 9 ++++-----
drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c | 5 +++--
9 files changed, 28 insertions(+), 34 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index de70c16ef619..7fc5bdb5cd9e 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2298,7 +2298,6 @@ static int i40e_run_xdp(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
struct bpf_prog *xdp_prog;
u32 act;
- rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@@ -2306,6 +2305,9 @@ static int i40e_run_xdp(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
prefetchw(xdp->data_hard_start); /* xdp_frame write */
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
act = bpf_prog_run_xdp(xdp_prog, xdp);
switch (act) {
case XDP_PASS:
@@ -2329,7 +2331,6 @@ static int i40e_run_xdp(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
break;
}
xdp_out:
- rcu_read_unlock();
return result;
}
diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index 46d884417c63..a5982cd112be 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
@@ -153,8 +153,10 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
struct bpf_prog *xdp_prog;
u32 act;
- rcu_read_lock();
- /* NB! xdp_prog will always be !NULL, due to the fact that
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ *
+ * NB! xdp_prog will always be !NULL, due to the fact that
* this path is enabled by setting an XDP program.
*/
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
@@ -162,9 +164,7 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
if (likely(act == XDP_REDIRECT)) {
err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
- result = !err ? I40E_XDP_REDIR : I40E_XDP_CONSUMED;
- rcu_read_unlock();
- return result;
+ return !err ? I40E_XDP_REDIR : I40E_XDP_CONSUMED;
}
switch (act) {
@@ -184,7 +184,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
result = I40E_XDP_CONSUMED;
break;
}
- rcu_read_unlock();
return result;
}
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index e2b4b29ea207..1a311e91fb6d 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -1129,15 +1129,11 @@ int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
xdp.frame_sz = ice_rx_frame_truesize(rx_ring, size);
#endif
- rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
- if (!xdp_prog) {
- rcu_read_unlock();
+ if (!xdp_prog)
goto construct_skb;
- }
xdp_res = ice_run_xdp(rx_ring, &xdp, xdp_prog);
- rcu_read_unlock();
if (!xdp_res)
goto construct_skb;
if (xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR)) {
diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index faa7b8d96adb..d6da377f5ac3 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -463,7 +463,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp)
struct ice_ring *xdp_ring;
u32 act;
- rcu_read_lock();
/* ZC patch is enabled only when XDP program is set,
* so here it can not be NULL
*/
@@ -473,9 +472,7 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp)
if (likely(act == XDP_REDIRECT)) {
err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
- result = !err ? ICE_XDP_REDIR : ICE_XDP_CONSUMED;
- rcu_read_unlock();
- return result;
+ return !err ? ICE_XDP_REDIR : ICE_XDP_CONSUMED;
}
switch (act) {
@@ -496,7 +493,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp)
break;
}
- rcu_read_unlock();
return result;
}
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 038a9fd1af44..0b68d589218a 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -8387,7 +8387,6 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter,
struct bpf_prog *xdp_prog;
u32 act;
- rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@@ -8395,6 +8394,9 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter,
prefetchw(xdp->data_hard_start); /* xdp_frame write */
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
act = bpf_prog_run_xdp(xdp_prog, xdp);
switch (act) {
case XDP_PASS:
@@ -8420,7 +8422,6 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter,
break;
}
xdp_out:
- rcu_read_unlock();
return ERR_PTR(-result);
}
diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index ea998d2defa4..333057ce60c7 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -2175,18 +2175,18 @@ static struct sk_buff *igc_xdp_run_prog(struct igc_adapter *adapter,
struct bpf_prog *prog;
int res;
- rcu_read_lock();
-
prog = READ_ONCE(adapter->xdp_prog);
if (!prog) {
res = IGC_XDP_PASS;
- goto unlock;
+ goto out;
}
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
res = __igc_xdp_run_prog(adapter, prog, xdp);
-unlock:
- rcu_read_unlock();
+out:
return ERR_PTR(-res);
}
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index c5ec17d19c59..9cebe7894111 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2199,7 +2199,6 @@ static struct sk_buff *ixgbe_run_xdp(struct ixgbe_adapter *adapter,
struct xdp_frame *xdpf;
u32 act;
- rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@@ -2207,6 +2206,9 @@ static struct sk_buff *ixgbe_run_xdp(struct ixgbe_adapter *adapter,
prefetchw(xdp->data_hard_start); /* xdp_frame write */
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
act = bpf_prog_run_xdp(xdp_prog, xdp);
switch (act) {
case XDP_PASS:
@@ -2237,7 +2239,6 @@ static struct sk_buff *ixgbe_run_xdp(struct ixgbe_adapter *adapter,
break;
}
xdp_out:
- rcu_read_unlock();
return ERR_PTR(-result);
}
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
index 91ad5b902673..4a075e667082 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
@@ -100,15 +100,15 @@ static int ixgbe_run_xdp_zc(struct ixgbe_adapter *adapter,
struct xdp_frame *xdpf;
u32 act;
- rcu_read_lock();
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
act = bpf_prog_run_xdp(xdp_prog, xdp);
if (likely(act == XDP_REDIRECT)) {
err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
- result = !err ? IXGBE_XDP_REDIR : IXGBE_XDP_CONSUMED;
- rcu_read_unlock();
- return result;
+ return !err ? IXGBE_XDP_REDIR : IXGBE_XDP_CONSUMED;
}
switch (act) {
@@ -132,7 +132,6 @@ static int ixgbe_run_xdp_zc(struct ixgbe_adapter *adapter,
result = IXGBE_XDP_CONSUMED;
break;
}
- rcu_read_unlock();
return result;
}
diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index ba2ed8a43d2d..ab05ebc3d350 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -1054,12 +1054,14 @@ static struct sk_buff *ixgbevf_run_xdp(struct ixgbevf_adapter *adapter,
struct bpf_prog *xdp_prog;
u32 act;
- rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
goto xdp_out;
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
act = bpf_prog_run_xdp(xdp_prog, xdp);
switch (act) {
case XDP_PASS:
@@ -1079,7 +1081,6 @@ static struct sk_buff *ixgbevf_run_xdp(struct ixgbevf_adapter *adapter,
break;
}
xdp_out:
- rcu_read_unlock();
return ERR_PTR(-result);
}
--
2.31.1
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