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/mtd/maps/solutionengine.c | 95 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 drivers/mtd/maps/solutionengine.c (limited to 'drivers/mtd/maps/solutionengine.c') diff --git a/drivers/mtd/maps/solutionengine.c b/drivers/mtd/maps/solutionengine.c new file mode 100644 index 000000000..c07f21b20 --- /dev/null +++ b/drivers/mtd/maps/solutionengine.c @@ -0,0 +1,95 @@ +/* + * Flash and EPROM on Hitachi Solution Engine and similar boards. + * + * (C) 2001 Red Hat, Inc. + * + * GPL'd + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static struct mtd_info *flash_mtd; +static struct mtd_info *eprom_mtd; + +struct map_info soleng_eprom_map = { + .name = "Solution Engine EPROM", + .size = 0x400000, + .bankwidth = 4, +}; + +struct map_info soleng_flash_map = { + .name = "Solution Engine FLASH", + .size = 0x400000, + .bankwidth = 4, +}; + +static const char * const probes[] = { "RedBoot", "cmdlinepart", NULL }; + +static int __init init_soleng_maps(void) +{ + /* First probe at offset 0 */ + soleng_flash_map.phys = 0; + soleng_flash_map.virt = (void __iomem *)P2SEGADDR(0); + soleng_eprom_map.phys = 0x01000000; + soleng_eprom_map.virt = (void __iomem *)P1SEGADDR(0x01000000); + simple_map_init(&soleng_eprom_map); + simple_map_init(&soleng_flash_map); + + printk(KERN_NOTICE "Probing for flash chips at 0x00000000:\n"); + flash_mtd = do_map_probe("cfi_probe", &soleng_flash_map); + if (!flash_mtd) { + /* Not there. Try swapping */ + printk(KERN_NOTICE "Probing for flash chips at 0x01000000:\n"); + soleng_flash_map.phys = 0x01000000; + soleng_flash_map.virt = P2SEGADDR(0x01000000); + soleng_eprom_map.phys = 0; + soleng_eprom_map.virt = P1SEGADDR(0); + flash_mtd = do_map_probe("cfi_probe", &soleng_flash_map); + if (!flash_mtd) { + /* Eep. */ + printk(KERN_NOTICE "Flash chips not detected at either possible location.\n"); + return -ENXIO; + } + } + printk(KERN_NOTICE "Solution Engine: Flash at 0x%pap, EPROM at 0x%pap\n", + &soleng_flash_map.phys, + &soleng_eprom_map.phys); + flash_mtd->owner = THIS_MODULE; + + eprom_mtd = do_map_probe("map_rom", &soleng_eprom_map); + if (eprom_mtd) { + eprom_mtd->owner = THIS_MODULE; + mtd_device_register(eprom_mtd, NULL, 0); + } + + mtd_device_parse_register(flash_mtd, probes, NULL, NULL, 0); + + return 0; +} + +static void __exit cleanup_soleng_maps(void) +{ + if (eprom_mtd) { + mtd_device_unregister(eprom_mtd); + map_destroy(eprom_mtd); + } + + mtd_device_unregister(flash_mtd); + map_destroy(flash_mtd); +} + +module_init(init_soleng_maps); +module_exit(cleanup_soleng_maps); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("David Woodhouse "); +MODULE_DESCRIPTION("MTD map driver for Hitachi SolutionEngine (and similar) boards"); + -- cgit v1.3.1