| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20250425175426.3353069-1-brianvv@google.com>
Date: Fri, 25 Apr 2025 17:54:26 +0000
From: Brian Vazquez <brianvv@...gle.com>
To: Brian Vazquez <brianvv.kernel@...il.com>, Tony Nguyen <anthony.l.nguyen@...el.com>,
Przemek Kitszel <przemyslaw.kitszel@...el.com>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
intel-wired-lan@...ts.osuosl.org
Cc: David Decotigny <decot@...gle.com>, Anjali Singhai <anjali.singhai@...el.com>,
Sridhar Samudrala <sridhar.samudrala@...el.com>, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, emil.s.tantilov@...el.com,
Brian Vazquez <brianvv@...gle.com>, Josh Hay <joshua.a.hay@...el.com>,
Luigi Rizzo <lrizzo@...gle.com>
Subject: [iwl-next PATCH] idpf: fix a race in txq wakeup
Add a helper function to correctly handle the lockless
synchronization when the sender needs to block. The paradigm is
if (no_resources()) {
stop_queue();
barrier();
if (!no_resources())
restart_queue();
}
netif_subqueue_maybe_stop already handles the paradigm correctly, but
the code split the check for resources in three parts, the first one
(descriptors) followed the protocol, but the other two (completions and
tx_buf) were only doing the first part and so race prone.
Luckly netif_subqueue_maybe_stop macro already allows you to use a
function to evaluate the start/stop conditions so the fix only requires
to pass the right helper function to evaluate all the conditions at once.
The patch removes idpf_tx_maybe_stop_common since it's no longer needed
and instead adjusts separetely the conditions for singleq and splitq.
Note that idpf_rx_buf_hw_update doesn't need to check for resources
since that will be covered in idpf_tx_splitq_frame.
To reproduce:
Reduce the threshold for pending completions to increase the chances of
hitting this pause by locally changing the kernel:
drivers/net/ethernet/intel/idpf/idpf_txrx.h
-#define IDPF_TX_COMPLQ_OVERFLOW_THRESH(txcq) ((txcq)->desc_count >> 1)
+#define IDPF_TX_COMPLQ_OVERFLOW_THRESH(txcq) ((txcq)->desc_count >> 4)
Use pktgen to force the host to push small pkts very aggresively:
./pktgen_sample02_multiqueue.sh -i eth1 -s 100 -6 -d $IP -m $MAC \
-p 10000-10000 -t 16 -n 0 -v -x -c 64
Signed-off-by: Josh Hay <joshua.a.hay@...el.com>
Signed-off-by: Brian Vazquez <brianvv@...gle.com>
Signed-off-by: Luigi Rizzo <lrizzo@...gle.com>
---
.../ethernet/intel/idpf/idpf_singleq_txrx.c | 9 ++--
drivers/net/ethernet/intel/idpf/idpf_txrx.c | 44 +++++++------------
drivers/net/ethernet/intel/idpf/idpf_txrx.h | 8 ----
3 files changed, 21 insertions(+), 40 deletions(-)
diff --git a/drivers/net/ethernet/intel/idpf/idpf_singleq_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_singleq_txrx.c
index c6b927fa9979..fb85270c69d6 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_singleq_txrx.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_singleq_txrx.c
@@ -364,15 +364,16 @@ netdev_tx_t idpf_tx_singleq_frame(struct sk_buff *skb,
struct idpf_tx_buf *first;
unsigned int count;
__be16 protocol;
- int csum, tso;
+ int csum, tso, needed;
count = idpf_tx_desc_count_required(tx_q, skb);
if (unlikely(!count))
return idpf_tx_drop_skb(tx_q, skb);
- if (idpf_tx_maybe_stop_common(tx_q,
- count + IDPF_TX_DESCS_PER_CACHE_LINE +
- IDPF_TX_DESCS_FOR_CTX)) {
+ needed = count + IDPF_TX_DESCS_PER_CACHE_LINE + IDPF_TX_DESCS_FOR_CTX;
+ if (!netif_subqueue_maybe_stop(tx_q->netdev, tx_q->idx,
+ IDPF_DESC_UNUSED(tx_q),
+ needed, needed)) {
idpf_tx_buf_hw_update(tx_q, tx_q->next_to_use, false);
u64_stats_update_begin(&tx_q->stats_sync);
diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
index 970fa9e5c39b..cb41b6fcf03f 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
@@ -2184,6 +2184,19 @@ void idpf_tx_splitq_build_flow_desc(union idpf_tx_flex_desc *desc,
desc->flow.qw1.compl_tag = cpu_to_le16(params->compl_tag);
}
+/* Global conditions to tell whether the txq (and related resources)
+ * has room to allow the use of "size" descriptors.
+ */
+static inline int txq_has_room(struct idpf_tx_queue *tx_q, u32 size)
+{
+ if (IDPF_DESC_UNUSED(tx_q) < size ||
+ IDPF_TX_COMPLQ_PENDING(tx_q->txq_grp) >
+ IDPF_TX_COMPLQ_OVERFLOW_THRESH(tx_q->txq_grp->complq) ||
+ IDPF_TX_BUF_RSV_LOW(tx_q))
+ return 0;
+ return 1;
+}
+
/**
* idpf_tx_maybe_stop_splitq - 1st level check for Tx splitq stop conditions
* @tx_q: the queue to be checked
@@ -2194,29 +2207,10 @@ void idpf_tx_splitq_build_flow_desc(union idpf_tx_flex_desc *desc,
static int idpf_tx_maybe_stop_splitq(struct idpf_tx_queue *tx_q,
unsigned int descs_needed)
{
- if (idpf_tx_maybe_stop_common(tx_q, descs_needed))
- goto out;
-
- /* If there are too many outstanding completions expected on the
- * completion queue, stop the TX queue to give the device some time to
- * catch up
- */
- if (unlikely(IDPF_TX_COMPLQ_PENDING(tx_q->txq_grp) >
- IDPF_TX_COMPLQ_OVERFLOW_THRESH(tx_q->txq_grp->complq)))
- goto splitq_stop;
-
- /* Also check for available book keeping buffers; if we are low, stop
- * the queue to wait for more completions
- */
- if (unlikely(IDPF_TX_BUF_RSV_LOW(tx_q)))
- goto splitq_stop;
-
- return 0;
-
-splitq_stop:
- netif_stop_subqueue(tx_q->netdev, tx_q->idx);
+ if (netif_subqueue_maybe_stop(tx_q->netdev, tx_q->idx,
+ txq_has_room(tx_q, descs_needed), 1, 1))
+ return 0;
-out:
u64_stats_update_begin(&tx_q->stats_sync);
u64_stats_inc(&tx_q->q_stats.q_busy);
u64_stats_update_end(&tx_q->stats_sync);
@@ -2242,12 +2236,6 @@ void idpf_tx_buf_hw_update(struct idpf_tx_queue *tx_q, u32 val,
nq = netdev_get_tx_queue(tx_q->netdev, tx_q->idx);
tx_q->next_to_use = val;
- if (idpf_tx_maybe_stop_common(tx_q, IDPF_TX_DESC_NEEDED)) {
- u64_stats_update_begin(&tx_q->stats_sync);
- u64_stats_inc(&tx_q->q_stats.q_busy);
- u64_stats_update_end(&tx_q->stats_sync);
- }
-
/* Force memory writes to complete before letting h/w
* know there are new descriptors to fetch. (Only
* applicable for weak-ordered memory model archs,
diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.h b/drivers/net/ethernet/intel/idpf/idpf_txrx.h
index c779fe71df99..36a0f828a6f8 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_txrx.h
+++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.h
@@ -1049,12 +1049,4 @@ bool idpf_rx_singleq_buf_hw_alloc_all(struct idpf_rx_queue *rxq,
u16 cleaned_count);
int idpf_tso(struct sk_buff *skb, struct idpf_tx_offload_params *off);
-static inline bool idpf_tx_maybe_stop_common(struct idpf_tx_queue *tx_q,
- u32 needed)
-{
- return !netif_subqueue_maybe_stop(tx_q->netdev, tx_q->idx,
- IDPF_DESC_UNUSED(tx_q),
- needed, needed);
-}
-
#endif /* !_IDPF_TXRX_H_ */
--
2.49.0.850.g28803427d3-goog
Powered by blists - more mailing lists