Subject: [net-next PATCH v3 1/4] net: introduce napi_is_scheduled helper

From: Christian Marangi <[email-masked]>
Date: Sat, 14 Oct 2023 11:29:51 +0200

We currently have napi_if_scheduled_mark_missed that can be used to
check if napi is scheduled but that does more thing than simply checking
it and return a bool. Some driver already implement custom function to
check if napi is scheduled.

Drop these custom function and introduce napi_is_scheduled that simply
check if napi is scheduled atomically.

Update any driver and code that implement a similar check and instead
use this new helper.

Signed-off-by: Christian Marangi <[email-masked]>
---
 drivers/net/ethernet/chelsio/cxgb3/sge.c  |  8 --------
 drivers/net/wireless/realtek/rtw89/core.c |  2 +-
 include/linux/netdevice.h                 | 23 +++++++++++++++++++++++
 net/core/dev.c                            |  2 +-
 4 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb3/sge.c b/drivers/net/ethernet/chelsio/cxgb3/sge.c
index 2e9a74fe0970..71fa2dc19034 100644
--- a/drivers/net/ethernet/chelsio/cxgb3/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb3/sge.c
@@ -2501,14 +2501,6 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 	return work_done;
 }
 
-/*
- * Returns true if the device is already scheduled for polling.
- */
-static inline int napi_is_scheduled(struct napi_struct *napi)
-{
-	return test_bit(NAPI_STATE_SCHED, &napi->state);
-}
-
 /**
  *	process_pure_responses - process pure responses from a response queue
  *	@adap: the adapter
diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index cca18d7ea1dd..6faf4dcf007c 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1919,7 +1919,7 @@ static void rtw89_core_rx_to_mac80211(struct rtw89_dev *rtwdev,
 	struct napi_struct *napi = &rtwdev->napi;
 
 	/* In low power mode, napi isn't scheduled. Receive it to netif. */
-	if (unlikely(!test_bit(NAPI_STATE_SCHED, &napi->state)))
+	if (unlikely(!napi_is_scheduled(napi)))
 		napi = NULL;
 
 	rtw89_core_hw_to_sband_rate(rx_status);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 1c7681263d30..b8bf669212cc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -482,6 +482,29 @@ static inline bool napi_prefer_busy_poll(struct napi_struct *n)
 	return test_bit(NAPI_STATE_PREFER_BUSY_POLL, &n->state);
 }
 
+/**
+ * napi_is_scheduled - test if NAPI is scheduled
+ * @n: NAPI context
+ *
+ * This check is "best-effort". With no locking implemented,
+ * a NAPI can be scheduled or terminate right after this check
+ * and produce not precise results.
+ *
+ * NAPI_STATE_SCHED is an internal state, napi_is_scheduled
+ * should not be used normally and napi_schedule should be
+ * used instead.
+ *
+ * Use only if the driver really needs to check if a NAPI
+ * is scheduled for example in the context of delayed timer
+ * that can be skipped if a NAPI is already scheduled.
+ *
+ * Return True if NAPI is scheduled, False otherwise.
+ */
+static inline bool napi_is_scheduled(struct napi_struct *n)
+{
+	return test_bit(NAPI_STATE_SCHED, &n->state);
+}
+
 bool napi_schedule_prep(struct napi_struct *n);
 
 /**
diff --git a/net/core/dev.c b/net/core/dev.c
index 3ca746a5f0ad..8d267fc0b988 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6527,7 +6527,7 @@ static int __napi_poll(struct napi_struct *n, bool *repoll)
 	 * accidentally calling ->poll() when NAPI is not scheduled.
 	 */
 	work = 0;
-	if (test_bit(NAPI_STATE_SCHED, &n->state)) {
+	if (napi_is_scheduled(n)) {
 		work = n->poll(n, weight);
 		trace_napi_poll(n, work, weight);
 	}
-- 
2.40.1