sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

alb_break_llc() decides whether to break LLC preference during active
load balance. It does so by testing that every runnable fair task on the
source rq prefers its LLC:

	env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable

But the two counters cover different sets. nr_pref_llc_running is updated
in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued,
so it follows queued tasks. h_nr_runnable is updated in set_delayed()/
clear_delayed() and drops delay-dequeued tasks.

So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted
in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks,
alb_break_llc() returns false, and active balance is free to pull a task
off its preferred LLC. Active balance only moves runnable tasks, and this
is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB
skips the per-task test in can_migrate_task(). The runnable set is the one
we want.

Fix it on the counter side. A task should be counted in
nr_pref_llc_running exactly while it is both queued on its preferred LLC
(pref_llc_queued) and runnable (!sched_delayed). Define that membership
once in task_pref_llc_runnable(), and adjust the counter only through
pref_llc_running_inc()/pref_llc_running_dec() from the four sites that
change either input: account_llc_enqueue(), account_llc_dequeue(),
set_delayed() and clear_delayed(). Gating every update on the same
predicate keeps the delay, wake and dequeue paths from double-counting
or underflowing; see the comments at those sites for the ordering.

nr_llc_running and sd->llc_counts are not touched and stay on queued
semantics.

Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC")
Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/
Reported-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 200 insertions, 0 deletions

diff --git a/drivers/net/phy/rockchip.c b/drivers/net/phy/rockchip.c
new file mode 100644
index 000000000..b338f385e
--- /dev/null
+++ b/drivers/net/phy/rockchip.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * drivers/net/phy/rockchip.c
+ *
+ * Driver for ROCKCHIP Ethernet PHYs
+ *
+ * Copyright (c) 2017, Fuzhou Rockchip Electronics Co., Ltd
+ *
+ * David Wu <david.wu@rock-chips.com>
+ */
+
+#include <linux/ethtool.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/netdevice.h>
+#include <linux/phy.h>
+
+#define INTERNAL_EPHY_ID			0x1234d400
+
+#define MII_INTERNAL_CTRL_STATUS		17
+#define SMI_ADDR_TSTCNTL			20
+#define SMI_ADDR_TSTREAD1			21
+#define SMI_ADDR_TSTREAD2			22
+#define SMI_ADDR_TSTWRITE			23
+#define MII_SPECIAL_CONTROL_STATUS		31
+
+#define MII_AUTO_MDIX_EN			BIT(7)
+#define MII_MDIX_EN				BIT(6)
+
+#define MII_SPEED_10				BIT(2)
+#define MII_SPEED_100				BIT(3)
+
+#define TSTCNTL_RD				(BIT(15) | BIT(10))
+#define TSTCNTL_WR				(BIT(14) | BIT(10))
+
+#define TSTMODE_ENABLE				0x400
+#define TSTMODE_DISABLE				0x0
+
+#define WR_ADDR_A7CFG				0x18
+
+static int rockchip_init_tstmode(struct phy_device *phydev)
+{
+	int ret;
+
+	/* Enable access to Analog and DSP register banks */
+	ret = phy_write(phydev, SMI_ADDR_TSTCNTL, TSTMODE_ENABLE);
+	if (ret)
+		return ret;
+
+	ret = phy_write(phydev, SMI_ADDR_TSTCNTL, TSTMODE_DISABLE);
+	if (ret)
+		return ret;
+
+	return phy_write(phydev, SMI_ADDR_TSTCNTL, TSTMODE_ENABLE);
+}
+
+static int rockchip_close_tstmode(struct phy_device *phydev)
+{
+	/* Back to basic register bank */
+	return phy_write(phydev, SMI_ADDR_TSTCNTL, TSTMODE_DISABLE);
+}
+
+static int rockchip_integrated_phy_analog_init(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = rockchip_init_tstmode(phydev);
+	if (ret)
+		return ret;
+
+	/*
+	 * Adjust tx amplitude to make sginal better,
+	 * the default value is 0x8.
+	 */
+	ret = phy_write(phydev, SMI_ADDR_TSTWRITE, 0xB);
+	if (ret)
+		return ret;
+	ret = phy_write(phydev, SMI_ADDR_TSTCNTL, TSTCNTL_WR | WR_ADDR_A7CFG);
+	if (ret)
+		return ret;
+
+	return rockchip_close_tstmode(phydev);
+}
+
+static int rockchip_integrated_phy_config_init(struct phy_device *phydev)
+{
+	int val, ret;
+
+	/*
+	 * The auto MIDX has linked problem on some board,
+	 * workround to disable auto MDIX.
+	 */
+	val = phy_read(phydev, MII_INTERNAL_CTRL_STATUS);
+	if (val < 0)
+		return val;
+	val &= ~MII_AUTO_MDIX_EN;
+	ret = phy_write(phydev, MII_INTERNAL_CTRL_STATUS, val);
+	if (ret)
+		return ret;
+
+	return rockchip_integrated_phy_analog_init(phydev);
+}
+
+static void rockchip_link_change_notify(struct phy_device *phydev)
+{
+	/*
+	 * If mode switch happens from 10BT to 100BT, all DSP/AFE
+	 * registers are set to default values. So any AFE/DSP
+	 * registers have to be re-initialized in this case.
+	 */
+	if (phydev->state == PHY_RUNNING && phydev->speed == SPEED_100) {
+		int ret = rockchip_integrated_phy_analog_init(phydev);
+
+		if (ret)
+			phydev_err(phydev, "rockchip_integrated_phy_analog_init err: %d.\n",
+				   ret);
+	}
+}
+
+static int rockchip_set_polarity(struct phy_device *phydev, int polarity)
+{
+	int reg, err, val;
+
+	/* get the current settings */
+	reg = phy_read(phydev, MII_INTERNAL_CTRL_STATUS);
+	if (reg < 0)
+		return reg;
+
+	reg &= ~MII_AUTO_MDIX_EN;
+	val = reg;
+	switch (polarity) {
+	case ETH_TP_MDI:
+		val &= ~MII_MDIX_EN;
+		break;
+	case ETH_TP_MDI_X:
+		val |= MII_MDIX_EN;
+		break;
+	case ETH_TP_MDI_AUTO:
+	case ETH_TP_MDI_INVALID:
+	default:
+		return 0;
+	}
+
+	if (val != reg) {
+		/* Set the new polarity value in the register */
+		err = phy_write(phydev, MII_INTERNAL_CTRL_STATUS, val);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int rockchip_config_aneg(struct phy_device *phydev)
+{
+	int err;
+
+	err = rockchip_set_polarity(phydev, phydev->mdix);
+	if (err < 0)
+		return err;
+
+	return genphy_config_aneg(phydev);
+}
+
+static int rockchip_phy_resume(struct phy_device *phydev)
+{
+	genphy_resume(phydev);
+
+	return rockchip_integrated_phy_config_init(phydev);
+}
+
+static struct phy_driver rockchip_phy_driver[] = {
+{
+	.phy_id			= INTERNAL_EPHY_ID,
+	.phy_id_mask		= 0xfffffff0,
+	.name			= "Rockchip integrated EPHY",
+	/* PHY_BASIC_FEATURES */
+	.flags			= 0,
+	.link_change_notify	= rockchip_link_change_notify,
+	.soft_reset		= genphy_soft_reset,
+	.config_init		= rockchip_integrated_phy_config_init,
+	.config_aneg		= rockchip_config_aneg,
+	.suspend		= genphy_suspend,
+	.resume			= rockchip_phy_resume,
+},
+};
+
+module_phy_driver(rockchip_phy_driver);
+
+static const struct mdio_device_id __maybe_unused rockchip_phy_tbl[] = {
+	{ INTERNAL_EPHY_ID, 0xfffffff0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, rockchip_phy_tbl);
+
+MODULE_AUTHOR("David Wu <david.wu@rock-chips.com>");
+MODULE_DESCRIPTION("Rockchip Ethernet PHY driver");
+MODULE_LICENSE("GPL");