From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug 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 Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- drivers/net/phy/amd.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 drivers/net/phy/amd.c (limited to 'drivers/net/phy/amd.c') diff --git a/drivers/net/phy/amd.c b/drivers/net/phy/amd.c new file mode 100644 index 000000000..75b5fe655 --- /dev/null +++ b/drivers/net/phy/amd.c @@ -0,0 +1,120 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Driver for AMD am79c PHYs + * + * Author: Heiko Schocher + * + * Copyright (c) 2011 DENX Software Engineering GmbH + */ +#include +#include +#include +#include +#include +#include + +#define PHY_ID_AC101L 0x00225520 +#define PHY_ID_AM79C874 0x0022561b + +#define MII_AM79C_IR 17 /* Interrupt Status/Control Register */ +#define MII_AM79C_IR_EN_LINK 0x0400 /* IR enable Linkstate */ +#define MII_AM79C_IR_EN_ANEG 0x0100 /* IR enable Aneg Complete */ +#define MII_AM79C_IR_IMASK_INIT (MII_AM79C_IR_EN_LINK | MII_AM79C_IR_EN_ANEG) + +#define MII_AM79C_IR_LINK_DOWN BIT(2) +#define MII_AM79C_IR_ANEG_DONE BIT(0) +#define MII_AM79C_IR_IMASK_STAT (MII_AM79C_IR_LINK_DOWN | MII_AM79C_IR_ANEG_DONE) + +MODULE_DESCRIPTION("AMD PHY driver"); +MODULE_AUTHOR("Heiko Schocher "); +MODULE_LICENSE("GPL"); + +static int am79c_ack_interrupt(struct phy_device *phydev) +{ + int err; + + err = phy_read(phydev, MII_BMSR); + if (err < 0) + return err; + + err = phy_read(phydev, MII_AM79C_IR); + if (err < 0) + return err; + + return 0; +} + +static int am79c_config_init(struct phy_device *phydev) +{ + return 0; +} + +static int am79c_config_intr(struct phy_device *phydev) +{ + int err; + + if (phydev->interrupts == PHY_INTERRUPT_ENABLED) { + err = am79c_ack_interrupt(phydev); + if (err) + return err; + + err = phy_write(phydev, MII_AM79C_IR, MII_AM79C_IR_IMASK_INIT); + } else { + err = phy_write(phydev, MII_AM79C_IR, 0); + if (err) + return err; + + err = am79c_ack_interrupt(phydev); + } + + return err; +} + +static irqreturn_t am79c_handle_interrupt(struct phy_device *phydev) +{ + int irq_status; + + irq_status = phy_read(phydev, MII_AM79C_IR); + if (irq_status < 0) { + phy_error(phydev); + return IRQ_NONE; + } + + if (!(irq_status & MII_AM79C_IR_IMASK_STAT)) + return IRQ_NONE; + + phy_trigger_machine(phydev); + + return IRQ_HANDLED; +} + +static struct phy_driver am79c_drivers[] = { + { + .phy_id = PHY_ID_AM79C874, + .name = "AM79C874", + .phy_id_mask = 0xfffffff0, + /* PHY_BASIC_FEATURES */ + .config_init = am79c_config_init, + .config_intr = am79c_config_intr, + .handle_interrupt = am79c_handle_interrupt, + }, + { + .phy_id = PHY_ID_AC101L, + .name = "AC101L", + .phy_id_mask = 0xfffffff0, + /* PHY_BASIC_FEATURES */ + .config_init = am79c_config_init, + .config_intr = am79c_config_intr, + .handle_interrupt = am79c_handle_interrupt, + }, +}; + +module_phy_driver(am79c_drivers); + +static const struct mdio_device_id __maybe_unused amd_tbl[] = { + { PHY_ID_AC101L, 0xfffffff0 }, + { PHY_ID_AM79C874, 0xfffffff0 }, + { } +}; + +MODULE_DEVICE_TABLE(mdio, amd_tbl); -- cgit v1.3.1