diff mbox series

[RFC,net-next,3/4] net: stmmac: do not use __netif_tx_lock_bh when in NAPI threaded mode

Message ID 20211210193556.1349090-4-yannick.vignon@oss.nxp.com (mailing list archive)
State RFC
Delegated to: Netdev Maintainers
Headers show
Series net: Improving network scheduling latencies | expand

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Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit fail Errors and warnings before: 0 this patch: 1
netdev/cc_maintainers warning 4 maintainers not CCed: linux-arm-kernel@lists.infradead.org linux-stm32@st-md-mailman.stormreply.com mcoquelin.stm32@gmail.com alexandre.torgue@foss.st.com
netdev/build_clang fail Errors and warnings before: 0 this patch: 1
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn fail Errors and warnings before: 0 this patch: 1
netdev/checkpatch warning WARNING: line length of 91 exceeds 80 columns WARNING: line length of 93 exceeds 80 columns
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netdev/source_inline success Was 0 now: 0

Commit Message

Yannick Vignon Dec. 10, 2021, 7:35 p.m. UTC 
From: Yannick Vignon <yannick.vignon@nxp.com>

In threaded mode, a NAPI instance can not execute concurrently in a
separate context but only in its assigned kernel thread.

Replace the calls to __netif_tx_lock_bh/__netif_tx_unlock_bh by their
non-bh version to avoid disabling BH in that case. This prevents high
priority traffic from being blocked by another piece of code already
running with BH disabled.

Signed-off-by: Yannick Vignon <yannick.vignon@nxp.com>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c    | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 8bf24902be3c..2190b40fa92e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2481,13 +2481,16 @@  static bool stmmac_xdp_xmit_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
  * @queue: TX queue index
  * Description: it reclaims the transmit resources after transmission completes.
  */
-static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
+static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue, bool is_threaded)
 {
 	struct stmmac_tx_queue *tx_q = &priv->tx_queue[queue];
 	unsigned int bytes_compl = 0, pkts_compl = 0;
 	unsigned int entry, xmits = 0, count = 0;
 
-	__netif_tx_lock_bh(netdev_get_tx_queue(priv->dev, queue));
+	if (is_threaded)
+		__netif_tx_lock(netdev_get_tx_queue(priv->dev, queue), smp_processor_id());
+	else
+		__netif_tx_lock_bh(netdev_get_tx_queue(priv->dev, queue));
 
 	priv->xstats.tx_clean++;
 
@@ -2646,7 +2649,10 @@  static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
 			      STMMAC_COAL_TIMER(priv->tx_coal_timer[queue]),
 			      HRTIMER_MODE_REL);
 
-	__netif_tx_unlock_bh(netdev_get_tx_queue(priv->dev, queue));
+	if (is_threaded)
+		__netif_tx_unlock(netdev_get_tx_queue(priv->dev, queue));
+	else
+		__netif_tx_unlock_bh(netdev_get_tx_queue(priv->dev, queue));
 
 	/* Combine decisions from TX clean and XSK TX */
 	return max(count, xmits);
@@ -5377,7 +5383,7 @@  static int stmmac_napi_poll_tx(struct napi_struct *napi, int budget)
 
 	priv->xstats.napi_poll++;
 
-	work_done = stmmac_tx_clean(priv, budget, chan);
+	work_done = stmmac_tx_clean(priv, budget, chan, !!napi->thread);
 	work_done = min(work_done, budget);
 
 	if (work_done < budget && napi_complete_done(napi, work_done)) {
@@ -5401,7 +5407,7 @@  static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget)
 
 	priv->xstats.napi_poll++;
 
-	tx_done = stmmac_tx_clean(priv, budget, chan);
+	tx_done = stmmac_tx_clean(priv, budget, chan, !!napi->thread);
 	tx_done = min(tx_done, budget);
 
 	rx_done = stmmac_rx_zc(priv, budget, chan);