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[v1,net-next,07/11] net: ena: Add more information on TX timeouts

Message ID 20240129085531.15608-8-darinzon@amazon.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series ENA driver changes | expand

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Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1064 this patch: 1064
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 0 of 0 maintainers
netdev/build_clang success Errors and warnings before: 1081 this patch: 1081
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1081 this patch: 1081
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns WARNING: line length of 83 exceeds 80 columns WARNING: line length of 84 exceeds 80 columns WARNING: line length of 86 exceeds 80 columns WARNING: line length of 88 exceeds 80 columns WARNING: line length of 90 exceeds 80 columns WARNING: line length of 92 exceeds 80 columns WARNING: line length of 95 exceeds 80 columns WARNING: line length of 96 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest pending net-next-2024-01-30--09-00

Commit Message

David Arinzon Jan. 29, 2024, 8:55 a.m. UTC
From: David Arinzon <darinzon@amazon.com>

The function responsible for polling TX completions might not receive
the CPU resources it needs due to higher priority tasks running on the
requested core.

The driver might not be able to recognize such cases, but it can use its
state to suspect that they happened. If both conditions are met:

- napi hasn't been executed more than the TX completion timeout value
- napi is scheduled (meaning that we've received an interrupt)

Then it's more likely that the napi handler isn't scheduled because of
an overloaded CPU.
It was decided that for this case, the driver would wait twice as long
as the regular timeout before scheduling a reset.
The driver uses ENA_REGS_RESET_SUSPECTED_POLL_STARVATION reset reason to
indicate this case to the device.

This patch also adds more information to the ena_tx_timeout() callback.
This function is called by the kernel when it detects that a specific TX
queue has been closed for too long.

Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: David Arinzon <darinzon@amazon.com>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c  | 77 +++++++++++++++----
 .../net/ethernet/amazon/ena/ena_regs_defs.h   |  1 +
 2 files changed, 64 insertions(+), 14 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 18acb76..ae9291b 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -47,19 +47,44 @@  static int ena_restore_device(struct ena_adapter *adapter);
 
 static void ena_tx_timeout(struct net_device *dev, unsigned int txqueue)
 {
+	enum ena_regs_reset_reason_types reset_reason = ENA_REGS_RESET_OS_NETDEV_WD;
 	struct ena_adapter *adapter = netdev_priv(dev);
+	unsigned int time_since_last_napi, threshold;
+	struct ena_ring *tx_ring;
+	int napi_scheduled;
+
+	if (txqueue >= adapter->num_io_queues) {
+		netdev_err(dev, "TX timeout on invalid queue %u\n", txqueue);
+		goto schedule_reset;
+	}
+
+	threshold = jiffies_to_usecs(dev->watchdog_timeo);
+	tx_ring = &adapter->tx_ring[txqueue];
+
+	time_since_last_napi = jiffies_to_usecs(jiffies - tx_ring->tx_stats.last_napi_jiffies);
+	napi_scheduled = !!(tx_ring->napi->state & NAPIF_STATE_SCHED);
 
+	netdev_err(dev,
+		   "TX q %d is paused for too long (threshold %u). Time since last napi %u usec. napi scheduled: %d\n",
+		   txqueue,
+		   threshold,
+		   time_since_last_napi,
+		   napi_scheduled);
+
+	if (threshold < time_since_last_napi && napi_scheduled) {
+		netdev_err(dev,
+			   "napi handler hasn't been called for a long time but is scheduled\n");
+			   reset_reason = ENA_REGS_RESET_SUSPECTED_POLL_STARVATION;
+	}
+schedule_reset:
 	/* Change the state of the device to trigger reset
 	 * Check that we are not in the middle or a trigger already
 	 */
-
 	if (test_and_set_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags))
 		return;
 
-	ena_reset_device(adapter, ENA_REGS_RESET_OS_NETDEV_WD);
+	ena_reset_device(adapter, reset_reason);
 	ena_increase_stat(&adapter->dev_stats.tx_timeout, 1, &adapter->syncp);
-
-	netif_err(adapter, tx_err, dev, "Transmit time out\n");
 }
 
 static void update_rx_ring_mtu(struct ena_adapter *adapter, int mtu)
@@ -3374,14 +3399,18 @@  static int check_missing_comp_in_tx_queue(struct ena_adapter *adapter,
 					  struct ena_ring *tx_ring)
 {
 	struct ena_napi *ena_napi = container_of(tx_ring->napi, struct ena_napi, napi);
+	enum ena_regs_reset_reason_types reset_reason = ENA_REGS_RESET_MISS_TX_CMPL;
 	unsigned int time_since_last_napi;
 	unsigned int missing_tx_comp_to;
 	bool is_tx_comp_time_expired;
 	struct ena_tx_buffer *tx_buf;
 	unsigned long last_jiffies;
+	int napi_scheduled;
 	u32 missed_tx = 0;
 	int i, rc = 0;
 
+	missing_tx_comp_to = jiffies_to_msecs(adapter->missing_tx_completion_to);
+
 	for (i = 0; i < tx_ring->ring_size; i++) {
 		tx_buf = &tx_ring->tx_buffer_info[i];
 		last_jiffies = tx_buf->last_jiffies;
@@ -3408,25 +3437,45 @@  static int check_missing_comp_in_tx_queue(struct ena_adapter *adapter,
 			adapter->missing_tx_completion_to);
 
 		if (unlikely(is_tx_comp_time_expired)) {
-			if (!tx_buf->print_once) {
-				time_since_last_napi = jiffies_to_usecs(jiffies - tx_ring->tx_stats.last_napi_jiffies);
-				missing_tx_comp_to = jiffies_to_msecs(adapter->missing_tx_completion_to);
-				netif_notice(adapter, tx_err, adapter->netdev,
-					     "Found a Tx that wasn't completed on time, qid %d, index %d. %u usecs have passed since last napi execution. Missing Tx timeout value %u msecs\n",
-					     tx_ring->qid, i, time_since_last_napi, missing_tx_comp_to);
+			time_since_last_napi =
+				jiffies_to_usecs(jiffies - tx_ring->tx_stats.last_napi_jiffies);
+			napi_scheduled = !!(ena_napi->napi.state & NAPIF_STATE_SCHED);
+
+			if (missing_tx_comp_to < time_since_last_napi && napi_scheduled) {
+				/* We suspect napi isn't called because the
+				 * bottom half is not run. Require a bigger
+				 * timeout for these cases
+				 */
+				if (!time_is_before_jiffies(last_jiffies +
+					2 * adapter->missing_tx_completion_to))
+					continue;
+
+				reset_reason = ENA_REGS_RESET_SUSPECTED_POLL_STARVATION;
 			}
 
-			tx_buf->print_once = 1;
 			missed_tx++;
+
+			if (tx_buf->print_once)
+				continue;
+
+			netif_notice(adapter, tx_err, adapter->netdev,
+				     "TX hasn't completed, qid %d, index %d. %u usecs from last napi execution, napi scheduled: %d\n",
+				     tx_ring->qid, i, time_since_last_napi, napi_scheduled);
+
+			tx_buf->print_once = 1;
 		}
 	}
 
 	if (unlikely(missed_tx > adapter->missing_tx_completion_threshold)) {
 		netif_err(adapter, tx_err, adapter->netdev,
-			  "The number of lost tx completions is above the threshold (%d > %d). Reset the device\n",
+			  "Lost TX completions are above the threshold (%d > %d). Completion transmission timeout: %u.\n",
 			  missed_tx,
-			  adapter->missing_tx_completion_threshold);
-		ena_reset_device(adapter, ENA_REGS_RESET_MISS_TX_CMPL);
+			  adapter->missing_tx_completion_threshold,
+			  missing_tx_comp_to);
+		netif_err(adapter, tx_err, adapter->netdev,
+			  "Resetting the device\n");
+
+		ena_reset_device(adapter, reset_reason);
 		rc = -EIO;
 	}
 
diff --git a/drivers/net/ethernet/amazon/ena/ena_regs_defs.h b/drivers/net/ethernet/amazon/ena/ena_regs_defs.h
index 1e007a4..2c3d6a7 100644
--- a/drivers/net/ethernet/amazon/ena/ena_regs_defs.h
+++ b/drivers/net/ethernet/amazon/ena/ena_regs_defs.h
@@ -21,6 +21,7 @@  enum ena_regs_reset_reason_types {
 	ENA_REGS_RESET_USER_TRIGGER                 = 12,
 	ENA_REGS_RESET_GENERIC                      = 13,
 	ENA_REGS_RESET_MISS_INTERRUPT               = 14,
+	ENA_REGS_RESET_SUSPECTED_POLL_STARVATION    = 15,
 };
 
 /* ena_registers offsets */