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, 259 insertions, 0 deletions

diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
new file mode 100644
index 000000000..1ad8fa3f8
--- /dev/null
+++ b/drivers/usb/dwc2/drd.c
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * drd.c - DesignWare USB2 DRD Controller Dual-role support
+ *
+ * Copyright (C) 2020 STMicroelectronics
+ *
+ * Author(s): Amelie Delaunay <amelie.delaunay@st.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/iopoll.h>
+#include <linux/platform_device.h>
+#include <linux/usb/role.h>
+#include "core.h"
+
+#define dwc2_ovr_gotgctl(gotgctl) \
+	((gotgctl) |= GOTGCTL_BVALOEN | GOTGCTL_AVALOEN | GOTGCTL_VBVALOEN | \
+	 GOTGCTL_DBNCE_FLTR_BYPASS)
+
+static void dwc2_ovr_init(struct dwc2_hsotg *hsotg)
+{
+	unsigned long flags;
+	u32 gotgctl;
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
+	gotgctl = dwc2_readl(hsotg, GOTGCTL);
+	dwc2_ovr_gotgctl(gotgctl);
+	gotgctl &= ~(GOTGCTL_BVALOVAL | GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL);
+	if (hsotg->role_sw_default_mode == USB_DR_MODE_HOST)
+		gotgctl |= GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL;
+	else if (hsotg->role_sw_default_mode == USB_DR_MODE_PERIPHERAL)
+		gotgctl |= GOTGCTL_BVALOVAL | GOTGCTL_VBVALOVAL;
+	dwc2_writel(hsotg, gotgctl, GOTGCTL);
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+
+	dwc2_force_mode(hsotg, (hsotg->dr_mode == USB_DR_MODE_HOST) ||
+				(hsotg->role_sw_default_mode == USB_DR_MODE_HOST));
+}
+
+static int dwc2_ovr_avalid(struct dwc2_hsotg *hsotg, bool valid)
+{
+	u32 gotgctl = dwc2_readl(hsotg, GOTGCTL);
+
+	/* Check if A-Session is already in the right state */
+	if ((valid && (gotgctl & GOTGCTL_ASESVLD)) ||
+	    (!valid && !(gotgctl & GOTGCTL_ASESVLD)))
+		return -EALREADY;
+
+	/* Always enable overrides to handle the resume case */
+	dwc2_ovr_gotgctl(gotgctl);
+
+	gotgctl &= ~GOTGCTL_BVALOVAL;
+	if (valid)
+		gotgctl |= GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL;
+	else
+		gotgctl &= ~(GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL);
+	dwc2_writel(hsotg, gotgctl, GOTGCTL);
+
+	return 0;
+}
+
+static int dwc2_ovr_bvalid(struct dwc2_hsotg *hsotg, bool valid)
+{
+	u32 gotgctl = dwc2_readl(hsotg, GOTGCTL);
+
+	/* Check if B-Session is already in the right state */
+	if ((valid && (gotgctl & GOTGCTL_BSESVLD)) ||
+	    (!valid && !(gotgctl & GOTGCTL_BSESVLD)))
+		return -EALREADY;
+
+	/* Always enable overrides to handle the resume case */
+	dwc2_ovr_gotgctl(gotgctl);
+
+	gotgctl &= ~GOTGCTL_AVALOVAL;
+	if (valid)
+		gotgctl |= GOTGCTL_BVALOVAL | GOTGCTL_VBVALOVAL;
+	else
+		gotgctl &= ~(GOTGCTL_BVALOVAL | GOTGCTL_VBVALOVAL);
+	dwc2_writel(hsotg, gotgctl, GOTGCTL);
+
+	return 0;
+}
+
+static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
+{
+	struct dwc2_hsotg *hsotg = usb_role_switch_get_drvdata(sw);
+	unsigned long flags;
+	int already = 0;
+
+	/* Skip session not in line with dr_mode */
+	if ((role == USB_ROLE_DEVICE && hsotg->dr_mode == USB_DR_MODE_HOST) ||
+	    (role == USB_ROLE_HOST && hsotg->dr_mode == USB_DR_MODE_PERIPHERAL))
+		return -EINVAL;
+
+#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
+	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
+	/* Skip session if core is in test mode */
+	if (role == USB_ROLE_NONE && hsotg->test_mode) {
+		dev_dbg(hsotg->dev, "Core is in test mode\n");
+		return -EBUSY;
+	}
+#endif
+
+	/*
+	 * In case of USB_DR_MODE_PERIPHERAL, clock is disabled at the end of
+	 * the probe and enabled on udc_start.
+	 * If role-switch set is called before the udc_start, we need to enable
+	 * the clock to read/write GOTGCTL and GUSBCFG registers to override
+	 * mode and sessions. It is the case if cable is plugged at boot.
+	 */
+	if (!hsotg->ll_hw_enabled && hsotg->clk) {
+		int ret = clk_prepare_enable(hsotg->clk);
+
+		if (ret)
+			return ret;
+	}
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
+	if (role == USB_ROLE_NONE) {
+		/* default operation mode when usb role is USB_ROLE_NONE */
+		if (hsotg->role_sw_default_mode == USB_DR_MODE_HOST)
+			role = USB_ROLE_HOST;
+		else if (hsotg->role_sw_default_mode == USB_DR_MODE_PERIPHERAL)
+			role = USB_ROLE_DEVICE;
+	}
+
+	if ((IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) ||
+	     IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)) &&
+	     dwc2_is_device_mode(hsotg) &&
+	     hsotg->lx_state == DWC2_L2 &&
+	     hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_NONE &&
+	     hsotg->bus_suspended &&
+	     !hsotg->params.no_clock_gating)
+		dwc2_gadget_exit_clock_gating(hsotg, 0);
+
+	if (role == USB_ROLE_HOST) {
+		already = dwc2_ovr_avalid(hsotg, true);
+	} else if (role == USB_ROLE_DEVICE) {
+		already = dwc2_ovr_bvalid(hsotg, true);
+		if (dwc2_is_device_enabled(hsotg)) {
+			/* This clear DCTL.SFTDISCON bit */
+			dwc2_hsotg_core_connect(hsotg);
+		}
+	} else {
+		if (dwc2_is_device_mode(hsotg)) {
+			if (!dwc2_ovr_bvalid(hsotg, false))
+				/* This set DCTL.SFTDISCON bit */
+				dwc2_hsotg_core_disconnect(hsotg);
+		} else {
+			dwc2_ovr_avalid(hsotg, false);
+		}
+	}
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+
+	if (!already && hsotg->dr_mode == USB_DR_MODE_OTG)
+		/* This will raise a Connector ID Status Change Interrupt */
+		dwc2_force_mode(hsotg, role == USB_ROLE_HOST);
+
+	if (!hsotg->ll_hw_enabled && hsotg->clk)
+		clk_disable_unprepare(hsotg->clk);
+
+	dev_dbg(hsotg->dev, "%s-session valid\n",
+		role == USB_ROLE_NONE ? "No" :
+		role == USB_ROLE_HOST ? "A" : "B");
+
+	return 0;
+}
+
+int dwc2_drd_init(struct dwc2_hsotg *hsotg)
+{
+	struct usb_role_switch_desc role_sw_desc = {0};
+	struct usb_role_switch *role_sw;
+	int ret;
+
+	if (!device_property_read_bool(hsotg->dev, "usb-role-switch"))
+		return 0;
+
+	hsotg->role_sw_default_mode = usb_get_role_switch_default_mode(hsotg->dev);
+	role_sw_desc.driver_data = hsotg;
+	role_sw_desc.fwnode = dev_fwnode(hsotg->dev);
+	role_sw_desc.set = dwc2_drd_role_sw_set;
+	role_sw_desc.allow_userspace_control = true;
+
+	role_sw = usb_role_switch_register(hsotg->dev, &role_sw_desc);
+	if (IS_ERR(role_sw)) {
+		ret = PTR_ERR(role_sw);
+		dev_err(hsotg->dev,
+			"failed to register role switch: %d\n", ret);
+		return ret;
+	}
+
+	hsotg->role_sw = role_sw;
+
+	/* Enable override and initialize values */
+	dwc2_ovr_init(hsotg);
+
+	return 0;
+}
+
+void dwc2_drd_suspend(struct dwc2_hsotg *hsotg)
+{
+	u32 gintsts, gintmsk;
+
+	if (hsotg->role_sw && !hsotg->params.external_id_pin_ctl) {
+		gintmsk = dwc2_readl(hsotg, GINTMSK);
+		gintmsk &= ~GINTSTS_CONIDSTSCHNG;
+		dwc2_writel(hsotg, gintmsk, GINTMSK);
+		gintsts = dwc2_readl(hsotg, GINTSTS);
+		dwc2_writel(hsotg, gintsts | GINTSTS_CONIDSTSCHNG, GINTSTS);
+	}
+}
+
+void dwc2_drd_resume(struct dwc2_hsotg *hsotg)
+{
+	u32 gintsts, gintmsk;
+	enum usb_role role;
+
+	if (hsotg->role_sw) {
+		/* get last known role (as the get ops isn't implemented by this driver) */
+		role = usb_role_switch_get_role(hsotg->role_sw);
+
+		if (role == USB_ROLE_NONE) {
+			if (hsotg->role_sw_default_mode == USB_DR_MODE_HOST)
+				role = USB_ROLE_HOST;
+			else if (hsotg->role_sw_default_mode == USB_DR_MODE_PERIPHERAL)
+				role = USB_ROLE_DEVICE;
+		}
+
+		/* restore last role that may have been lost */
+		if (role == USB_ROLE_HOST)
+			dwc2_ovr_avalid(hsotg, true);
+		else if (role == USB_ROLE_DEVICE)
+			dwc2_ovr_bvalid(hsotg, true);
+
+		dwc2_force_mode(hsotg, role == USB_ROLE_HOST);
+
+		dev_dbg(hsotg->dev, "resuming %s-session valid\n",
+			role == USB_ROLE_NONE ? "No" :
+			role == USB_ROLE_HOST ? "A" : "B");
+	}
+
+	if (hsotg->role_sw && !hsotg->params.external_id_pin_ctl) {
+		gintsts = dwc2_readl(hsotg, GINTSTS);
+		dwc2_writel(hsotg, gintsts | GINTSTS_CONIDSTSCHNG, GINTSTS);
+		gintmsk = dwc2_readl(hsotg, GINTMSK);
+		gintmsk |= GINTSTS_CONIDSTSCHNG;
+		dwc2_writel(hsotg, gintmsk, GINTMSK);
+	}
+}
+
+void dwc2_drd_exit(struct dwc2_hsotg *hsotg)
+{
+	if (hsotg->role_sw)
+		usb_role_switch_unregister(hsotg->role_sw);
+}