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, 419 insertions, 0 deletions

diff --git a/drivers/edac/qcom_edac.c b/drivers/edac/qcom_edac.c
new file mode 100644
index 000000000..f3da9385c
--- /dev/null
+++ b/drivers/edac/qcom_edac.c
@@ -0,0 +1,419 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/edac.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/soc/qcom/llcc-qcom.h>
+
+#include "edac_mc.h"
+#include "edac_device.h"
+
+#define EDAC_LLCC                       "qcom_llcc"
+
+#define LLCC_ERP_PANIC_ON_UE            1
+
+#define TRP_SYN_REG_CNT                 6
+#define DRP_SYN_REG_CNT                 8
+
+#define LLCC_LB_CNT_MASK                GENMASK(31, 28)
+#define LLCC_LB_CNT_SHIFT               28
+
+/* Mask and shift macros */
+#define ECC_DB_ERR_COUNT_MASK           GENMASK(4, 0)
+#define ECC_DB_ERR_WAYS_MASK            GENMASK(31, 16)
+#define ECC_DB_ERR_WAYS_SHIFT           BIT(4)
+
+#define ECC_SB_ERR_COUNT_MASK           GENMASK(23, 16)
+#define ECC_SB_ERR_COUNT_SHIFT          BIT(4)
+#define ECC_SB_ERR_WAYS_MASK            GENMASK(15, 0)
+
+#define SB_ECC_ERROR                    BIT(0)
+#define DB_ECC_ERROR                    BIT(1)
+
+#define DRP_TRP_INT_CLEAR               GENMASK(1, 0)
+#define DRP_TRP_CNT_CLEAR               GENMASK(1, 0)
+
+#define SB_ERROR_THRESHOLD              0x1
+#define SB_ERROR_THRESHOLD_SHIFT        24
+#define SB_DB_TRP_INTERRUPT_ENABLE      0x3
+#define TRP0_INTERRUPT_ENABLE           0x1
+#define DRP0_INTERRUPT_ENABLE           BIT(6)
+#define SB_DB_DRP_INTERRUPT_ENABLE      0x3
+
+#define ECC_POLL_MSEC			5000
+
+enum {
+	LLCC_DRAM_CE = 0,
+	LLCC_DRAM_UE,
+	LLCC_TRAM_CE,
+	LLCC_TRAM_UE,
+};
+
+static const struct llcc_edac_reg_data edac_reg_data[] = {
+	[LLCC_DRAM_CE] = {
+		.name = "DRAM Single-bit",
+		.reg_cnt = DRP_SYN_REG_CNT,
+		.count_mask = ECC_SB_ERR_COUNT_MASK,
+		.ways_mask = ECC_SB_ERR_WAYS_MASK,
+		.count_shift = ECC_SB_ERR_COUNT_SHIFT,
+	},
+	[LLCC_DRAM_UE] = {
+		.name = "DRAM Double-bit",
+		.reg_cnt = DRP_SYN_REG_CNT,
+		.count_mask = ECC_DB_ERR_COUNT_MASK,
+		.ways_mask = ECC_DB_ERR_WAYS_MASK,
+		.ways_shift = ECC_DB_ERR_WAYS_SHIFT,
+	},
+	[LLCC_TRAM_CE] = {
+		.name = "TRAM Single-bit",
+		.reg_cnt = TRP_SYN_REG_CNT,
+		.count_mask = ECC_SB_ERR_COUNT_MASK,
+		.ways_mask = ECC_SB_ERR_WAYS_MASK,
+		.count_shift = ECC_SB_ERR_COUNT_SHIFT,
+	},
+	[LLCC_TRAM_UE] = {
+		.name = "TRAM Double-bit",
+		.reg_cnt = TRP_SYN_REG_CNT,
+		.count_mask = ECC_DB_ERR_COUNT_MASK,
+		.ways_mask = ECC_DB_ERR_WAYS_MASK,
+		.ways_shift = ECC_DB_ERR_WAYS_SHIFT,
+	},
+};
+
+static int qcom_llcc_core_setup(struct llcc_drv_data *drv, struct regmap *llcc_bcast_regmap)
+{
+	u32 sb_err_threshold;
+	int ret;
+
+	/*
+	 * Configure interrupt enable registers such that Tag, Data RAM related
+	 * interrupts are propagated to interrupt controller for servicing
+	 */
+	ret = regmap_update_bits(llcc_bcast_regmap, drv->edac_reg_offset->cmn_interrupt_0_enable,
+				 TRP0_INTERRUPT_ENABLE,
+				 TRP0_INTERRUPT_ENABLE);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(llcc_bcast_regmap, drv->edac_reg_offset->trp_interrupt_0_enable,
+				 SB_DB_TRP_INTERRUPT_ENABLE,
+				 SB_DB_TRP_INTERRUPT_ENABLE);
+	if (ret)
+		return ret;
+
+	sb_err_threshold = (SB_ERROR_THRESHOLD << SB_ERROR_THRESHOLD_SHIFT);
+	ret = regmap_write(llcc_bcast_regmap, drv->edac_reg_offset->drp_ecc_error_cfg,
+			   sb_err_threshold);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(llcc_bcast_regmap, drv->edac_reg_offset->cmn_interrupt_0_enable,
+				 DRP0_INTERRUPT_ENABLE,
+				 DRP0_INTERRUPT_ENABLE);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(llcc_bcast_regmap, drv->edac_reg_offset->drp_interrupt_enable,
+			   SB_DB_DRP_INTERRUPT_ENABLE);
+	return ret;
+}
+
+/* Clear the error interrupt and counter registers */
+static int
+qcom_llcc_clear_error_status(int err_type, struct llcc_drv_data *drv)
+{
+	int ret;
+
+	switch (err_type) {
+	case LLCC_DRAM_CE:
+	case LLCC_DRAM_UE:
+		ret = regmap_write(drv->bcast_regmap,
+				   drv->edac_reg_offset->drp_interrupt_clear,
+				   DRP_TRP_INT_CLEAR);
+		if (ret)
+			return ret;
+
+		ret = regmap_write(drv->bcast_regmap,
+				   drv->edac_reg_offset->drp_ecc_error_cntr_clear,
+				   DRP_TRP_CNT_CLEAR);
+		if (ret)
+			return ret;
+		break;
+	case LLCC_TRAM_CE:
+	case LLCC_TRAM_UE:
+		ret = regmap_write(drv->bcast_regmap,
+				   drv->edac_reg_offset->trp_interrupt_0_clear,
+				   DRP_TRP_INT_CLEAR);
+		if (ret)
+			return ret;
+
+		ret = regmap_write(drv->bcast_regmap,
+				   drv->edac_reg_offset->trp_ecc_error_cntr_clear,
+				   DRP_TRP_CNT_CLEAR);
+		if (ret)
+			return ret;
+		break;
+	default:
+		ret = -EINVAL;
+		edac_printk(KERN_CRIT, EDAC_LLCC, "Unexpected error type: %d\n",
+			    err_type);
+	}
+	return ret;
+}
+
+struct qcom_llcc_syn_regs {
+	u32 synd_reg;
+	u32 count_status_reg;
+	u32 ways_status_reg;
+};
+
+static void get_reg_offsets(struct llcc_drv_data *drv, int err_type,
+			    struct qcom_llcc_syn_regs *syn_regs)
+{
+	const struct llcc_edac_reg_offset *edac_reg_offset = drv->edac_reg_offset;
+
+	switch (err_type) {
+	case LLCC_DRAM_CE:
+		syn_regs->synd_reg = edac_reg_offset->drp_ecc_sb_err_syn0;
+		syn_regs->count_status_reg = edac_reg_offset->drp_ecc_error_status1;
+		syn_regs->ways_status_reg = edac_reg_offset->drp_ecc_error_status0;
+		break;
+	case LLCC_DRAM_UE:
+		syn_regs->synd_reg = edac_reg_offset->drp_ecc_db_err_syn0;
+		syn_regs->count_status_reg = edac_reg_offset->drp_ecc_error_status1;
+		syn_regs->ways_status_reg = edac_reg_offset->drp_ecc_error_status0;
+		break;
+	case LLCC_TRAM_CE:
+		syn_regs->synd_reg = edac_reg_offset->trp_ecc_sb_err_syn0;
+		syn_regs->count_status_reg = edac_reg_offset->trp_ecc_error_status1;
+		syn_regs->ways_status_reg = edac_reg_offset->trp_ecc_error_status0;
+		break;
+	case LLCC_TRAM_UE:
+		syn_regs->synd_reg = edac_reg_offset->trp_ecc_db_err_syn0;
+		syn_regs->count_status_reg = edac_reg_offset->trp_ecc_error_status1;
+		syn_regs->ways_status_reg = edac_reg_offset->trp_ecc_error_status0;
+		break;
+	}
+}
+
+/* Dump Syndrome registers data for Tag RAM, Data RAM bit errors*/
+static int
+dump_syn_reg_values(struct llcc_drv_data *drv, u32 bank, int err_type)
+{
+	struct llcc_edac_reg_data reg_data = edac_reg_data[err_type];
+	struct qcom_llcc_syn_regs regs = { };
+	int err_cnt, err_ways, ret, i;
+	u32 synd_reg, synd_val;
+
+	get_reg_offsets(drv, err_type, &regs);
+
+	for (i = 0; i < reg_data.reg_cnt; i++) {
+		synd_reg = regs.synd_reg + (i * 4);
+		ret = regmap_read(drv->regmaps[bank], synd_reg,
+				  &synd_val);
+		if (ret)
+			goto clear;
+
+		edac_printk(KERN_CRIT, EDAC_LLCC, "%s: ECC_SYN%d: 0x%8x\n",
+			    reg_data.name, i, synd_val);
+	}
+
+	ret = regmap_read(drv->regmaps[bank], regs.count_status_reg,
+			  &err_cnt);
+	if (ret)
+		goto clear;
+
+	err_cnt &= reg_data.count_mask;
+	err_cnt >>= reg_data.count_shift;
+	edac_printk(KERN_CRIT, EDAC_LLCC, "%s: Error count: 0x%4x\n",
+		    reg_data.name, err_cnt);
+
+	ret = regmap_read(drv->regmaps[bank], regs.ways_status_reg,
+			  &err_ways);
+	if (ret)
+		goto clear;
+
+	err_ways &= reg_data.ways_mask;
+	err_ways >>= reg_data.ways_shift;
+
+	edac_printk(KERN_CRIT, EDAC_LLCC, "%s: Error ways: 0x%4x\n",
+		    reg_data.name, err_ways);
+
+clear:
+	return qcom_llcc_clear_error_status(err_type, drv);
+}
+
+static int
+dump_syn_reg(struct edac_device_ctl_info *edev_ctl, int err_type, u32 bank)
+{
+	struct llcc_drv_data *drv = edev_ctl->dev->platform_data;
+	int ret;
+
+	ret = dump_syn_reg_values(drv, bank, err_type);
+	if (ret)
+		return ret;
+
+	switch (err_type) {
+	case LLCC_DRAM_CE:
+		edac_device_handle_ce(edev_ctl, 0, bank,
+				      "LLCC Data RAM correctable Error");
+		break;
+	case LLCC_DRAM_UE:
+		edac_device_handle_ue(edev_ctl, 0, bank,
+				      "LLCC Data RAM uncorrectable Error");
+		break;
+	case LLCC_TRAM_CE:
+		edac_device_handle_ce(edev_ctl, 0, bank,
+				      "LLCC Tag RAM correctable Error");
+		break;
+	case LLCC_TRAM_UE:
+		edac_device_handle_ue(edev_ctl, 0, bank,
+				      "LLCC Tag RAM uncorrectable Error");
+		break;
+	default:
+		ret = -EINVAL;
+		edac_printk(KERN_CRIT, EDAC_LLCC, "Unexpected error type: %d\n",
+			    err_type);
+	}
+
+	return ret;
+}
+
+static irqreturn_t llcc_ecc_irq_handler(int irq, void *edev_ctl)
+{
+	struct edac_device_ctl_info *edac_dev_ctl = edev_ctl;
+	struct llcc_drv_data *drv = edac_dev_ctl->dev->platform_data;
+	irqreturn_t irq_rc = IRQ_NONE;
+	u32 drp_error, trp_error, i;
+	int ret;
+
+	/* Iterate over the banks and look for Tag RAM or Data RAM errors */
+	for (i = 0; i < drv->num_banks; i++) {
+		ret = regmap_read(drv->regmaps[i], drv->edac_reg_offset->drp_interrupt_status,
+				  &drp_error);
+
+		if (!ret && (drp_error & SB_ECC_ERROR)) {
+			edac_printk(KERN_CRIT, EDAC_LLCC,
+				    "Single Bit Error detected in Data RAM\n");
+			ret = dump_syn_reg(edev_ctl, LLCC_DRAM_CE, i);
+		} else if (!ret && (drp_error & DB_ECC_ERROR)) {
+			edac_printk(KERN_CRIT, EDAC_LLCC,
+				    "Double Bit Error detected in Data RAM\n");
+			ret = dump_syn_reg(edev_ctl, LLCC_DRAM_UE, i);
+		}
+		if (!ret)
+			irq_rc = IRQ_HANDLED;
+
+		ret = regmap_read(drv->regmaps[i], drv->edac_reg_offset->trp_interrupt_0_status,
+				  &trp_error);
+
+		if (!ret && (trp_error & SB_ECC_ERROR)) {
+			edac_printk(KERN_CRIT, EDAC_LLCC,
+				    "Single Bit Error detected in Tag RAM\n");
+			ret = dump_syn_reg(edev_ctl, LLCC_TRAM_CE, i);
+		} else if (!ret && (trp_error & DB_ECC_ERROR)) {
+			edac_printk(KERN_CRIT, EDAC_LLCC,
+				    "Double Bit Error detected in Tag RAM\n");
+			ret = dump_syn_reg(edev_ctl, LLCC_TRAM_UE, i);
+		}
+		if (!ret)
+			irq_rc = IRQ_HANDLED;
+	}
+
+	return irq_rc;
+}
+
+static void llcc_ecc_check(struct edac_device_ctl_info *edev_ctl)
+{
+	llcc_ecc_irq_handler(0, edev_ctl);
+}
+
+static int qcom_llcc_edac_probe(struct platform_device *pdev)
+{
+	struct llcc_drv_data *llcc_driv_data = pdev->dev.platform_data;
+	struct edac_device_ctl_info *edev_ctl;
+	struct device *dev = &pdev->dev;
+	int ecc_irq;
+	int rc;
+
+	if (!llcc_driv_data->ecc_irq_configured) {
+		rc = qcom_llcc_core_setup(llcc_driv_data, llcc_driv_data->bcast_regmap);
+		if (rc)
+			return rc;
+	}
+
+	/* Allocate edac control info */
+	edev_ctl = edac_device_alloc_ctl_info(0, "qcom-llcc", 1, "bank",
+					      llcc_driv_data->num_banks, 1,
+					      edac_device_alloc_index());
+
+	if (!edev_ctl)
+		return -ENOMEM;
+
+	edev_ctl->dev = dev;
+	edev_ctl->mod_name = dev_name(dev);
+	edev_ctl->dev_name = dev_name(dev);
+	edev_ctl->ctl_name = "llcc";
+	edev_ctl->panic_on_ue = LLCC_ERP_PANIC_ON_UE;
+
+	/* Check if LLCC driver has passed ECC IRQ */
+	ecc_irq = llcc_driv_data->ecc_irq;
+	if (ecc_irq > 0) {
+		/* Use interrupt mode if IRQ is available */
+		rc = devm_request_irq(dev, ecc_irq, llcc_ecc_irq_handler,
+			      IRQF_TRIGGER_HIGH, "llcc_ecc", edev_ctl);
+		if (!rc) {
+			edac_op_state = EDAC_OPSTATE_INT;
+			goto irq_done;
+		}
+	}
+
+	/* Fall back to polling mode otherwise */
+	edev_ctl->poll_msec = ECC_POLL_MSEC;
+	edev_ctl->edac_check = llcc_ecc_check;
+	edac_op_state = EDAC_OPSTATE_POLL;
+
+irq_done:
+	rc = edac_device_add_device(edev_ctl);
+	if (rc) {
+		edac_device_free_ctl_info(edev_ctl);
+		return rc;
+	}
+
+	platform_set_drvdata(pdev, edev_ctl);
+
+	return rc;
+}
+
+static void qcom_llcc_edac_remove(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edev_ctl = dev_get_drvdata(&pdev->dev);
+
+	edac_device_del_device(edev_ctl->dev);
+	edac_device_free_ctl_info(edev_ctl);
+}
+
+static const struct platform_device_id qcom_llcc_edac_id_table[] = {
+	{ .name = "qcom_llcc_edac" },
+	{}
+};
+MODULE_DEVICE_TABLE(platform, qcom_llcc_edac_id_table);
+
+static struct platform_driver qcom_llcc_edac_driver = {
+	.probe = qcom_llcc_edac_probe,
+	.remove = qcom_llcc_edac_remove,
+	.driver = {
+		.name = "qcom_llcc_edac",
+	},
+	.id_table = qcom_llcc_edac_id_table,
+};
+module_platform_driver(qcom_llcc_edac_driver);
+
+MODULE_DESCRIPTION("QCOM EDAC driver");
+MODULE_LICENSE("GPL v2");