netdev - [PATCH RFC net-next 6/7] net: phy: split locked and unlocked section of phy_state

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Message-Id: <E1qeZXy-007G4h-Uj@rmk-PC.armlinux.org.uk>
Date: Fri, 08 Sep 2023 12:21:10 +0100
From: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>
Cc: Jijie Shao <shaojijie@...wei.com>,
	 shaojijie@...wei.com,
	 shenjian15@...wei.com,
	 liuyonglong@...wei.com,
	 wangjie125@...wei.com,
	 chenhao418@...wei.com,
	 lanhao@...wei.com,
	 wangpeiyang1@...wei.com,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org
Subject: [PATCH RFC net-next 6/7] net: phy: split locked and unlocked section
 of phy_state_machine()

Split out the locked and unlocked sections of phy_state_machine() into
two separate functions which can be called inside the phydev lock and
outside the phydev lock as appropriate, thus allowing us to combine
the locked regions in the caller of phy_state_machine() with the
locked region inside phy_state_machine().

This avoids unnecessarily dropping the phydev lock which may allow
races to occur.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 drivers/net/phy/phy.c | 68 ++++++++++++++++++++++++++-----------------
 1 file changed, 42 insertions(+), 26 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 20e23fa9cf96..d78c2cc003ce 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -1353,33 +1353,27 @@ void phy_free_interrupt(struct phy_device *phydev)
 }
 EXPORT_SYMBOL(phy_free_interrupt);
 
-/**
- * phy_state_machine - Handle the state machine
- * @work: work_struct that describes the work to be done
- */
-void phy_state_machine(struct work_struct *work)
+enum phy_state_work {
+	PHY_STATE_WORK_NONE,
+	PHY_STATE_WORK_ANEG,
+	PHY_STATE_WORK_SUSPEND,
+};
+
+static enum phy_state_work _phy_state_machine(struct phy_device *phydev)
 {
-	struct delayed_work *dwork = to_delayed_work(work);
-	struct phy_device *phydev =
-			container_of(dwork, struct phy_device, state_queue);
+	enum phy_state_work state_work = PHY_STATE_WORK_NONE;
 	struct net_device *dev = phydev->attached_dev;
-	bool needs_aneg = false, do_suspend = false;
-	enum phy_state old_state;
+	enum phy_state old_state = phydev->state;
 	const void *func = NULL;
 	bool finished = false;
 	int err = 0;
 
-	mutex_lock(&phydev->lock);
-
-	old_state = phydev->state;
-
 	switch (phydev->state) {
 	case PHY_DOWN:
 	case PHY_READY:
 		break;
 	case PHY_UP:
-		needs_aneg = true;
-
+		state_work = PHY_STATE_WORK_ANEG;
 		break;
 	case PHY_NOLINK:
 	case PHY_RUNNING:
@@ -1391,7 +1385,7 @@ void phy_state_machine(struct work_struct *work)
 		if (err) {
 			phy_abort_cable_test(phydev);
 			netif_testing_off(dev);
-			needs_aneg = true;
+			state_work = PHY_STATE_WORK_ANEG;
 			phydev->state = PHY_UP;
 			break;
 		}
@@ -1399,7 +1393,7 @@ void phy_state_machine(struct work_struct *work)
 		if (finished) {
 			ethnl_cable_test_finished(phydev);
 			netif_testing_off(dev);
-			needs_aneg = true;
+			state_work = PHY_STATE_WORK_ANEG;
 			phydev->state = PHY_UP;
 		}
 		break;
@@ -1409,19 +1403,17 @@ void phy_state_machine(struct work_struct *work)
 			phydev->link = 0;
 			phy_link_down(phydev);
 		}
-		do_suspend = true;
+		state_work = PHY_STATE_WORK_SUSPEND;
 		break;
 	}
 
-	if (needs_aneg) {
+	if (state_work == PHY_STATE_WORK_ANEG) {
 		err = _phy_start_aneg(phydev);
 		func = &_phy_start_aneg;
 	}
 
-	if (err == -ENODEV) {
-		mutex_unlock(&phydev->lock);
-		return;
-	}
+	if (err == -ENODEV)
+		return state_work;
 
 	if (err < 0)
 		phy_error_precise(phydev, func, err);
@@ -1438,12 +1430,36 @@ void phy_state_machine(struct work_struct *work)
 	 */
 	if (phy_polling_mode(phydev) && phy_is_started(phydev))
 		phy_queue_state_machine(phydev, PHY_STATE_TIME);
-	mutex_unlock(&phydev->lock);
 
-	if (do_suspend)
+	return state_work;
+}
+
+/* unlocked part of the PHY state machine */
+static void _phy_state_machine_post_work(struct phy_device *phydev,
+					 enum phy_state_work state_work)
+{
+	if (state_work == PHY_STATE_WORK_SUSPEND)
 		phy_suspend(phydev);
 }
 
+/**
+ * phy_state_machine - Handle the state machine
+ * @work: work_struct that describes the work to be done
+ */
+void phy_state_machine(struct work_struct *work)
+{
+	struct delayed_work *dwork = to_delayed_work(work);
+	struct phy_device *phydev =
+			container_of(dwork, struct phy_device, state_queue);
+	enum phy_state_work state_work;
+
+	mutex_lock(&phydev->lock);
+	state_work = _phy_state_machine(phydev);
+	mutex_unlock(&phydev->lock);
+
+	_phy_state_machine_post_work(phydev, state_work);
+}
+
 /**
  * phy_stop - Bring down the PHY link, and stop checking the status
  * @phydev: target phy_device struct
-- 
2.30.2