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/fpga/xilinx-selectmap.c | 94 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 drivers/fpga/xilinx-selectmap.c (limited to 'drivers/fpga/xilinx-selectmap.c') diff --git a/drivers/fpga/xilinx-selectmap.c b/drivers/fpga/xilinx-selectmap.c new file mode 100644 index 000000000..d0cbb5fdf --- /dev/null +++ b/drivers/fpga/xilinx-selectmap.c @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Xilinx Spartan6 and 7 Series SelectMAP interface driver + * + * (C) 2024 Charles Perry + * + * Manage Xilinx FPGA firmware loaded over the SelectMAP configuration + * interface. + */ + +#include "xilinx-core.h" + +#include +#include +#include +#include +#include + +struct xilinx_selectmap_conf { + struct xilinx_fpga_core core; + void __iomem *base; +}; + +#define to_xilinx_selectmap_conf(obj) \ + container_of(obj, struct xilinx_selectmap_conf, core) + +static int xilinx_selectmap_write(struct xilinx_fpga_core *core, + const char *buf, size_t count) +{ + struct xilinx_selectmap_conf *conf = to_xilinx_selectmap_conf(core); + size_t i; + + for (i = 0; i < count; ++i) + writeb(buf[i], conf->base); + + return 0; +} + +static int xilinx_selectmap_probe(struct platform_device *pdev) +{ + struct xilinx_selectmap_conf *conf; + struct gpio_desc *gpio; + void __iomem *base; + + conf = devm_kzalloc(&pdev->dev, sizeof(*conf), GFP_KERNEL); + if (!conf) + return -ENOMEM; + + conf->core.dev = &pdev->dev; + conf->core.write = xilinx_selectmap_write; + + base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL); + if (IS_ERR(base)) + return dev_err_probe(&pdev->dev, PTR_ERR(base), + "ioremap error\n"); + conf->base = base; + + /* CSI_B is active low */ + gpio = devm_gpiod_get_optional(&pdev->dev, "csi", GPIOD_OUT_HIGH); + if (IS_ERR(gpio)) + return dev_err_probe(&pdev->dev, PTR_ERR(gpio), + "Failed to get CSI_B gpio\n"); + + /* RDWR_B is active low */ + gpio = devm_gpiod_get_optional(&pdev->dev, "rdwr", GPIOD_OUT_HIGH); + if (IS_ERR(gpio)) + return dev_err_probe(&pdev->dev, PTR_ERR(gpio), + "Failed to get RDWR_B gpio\n"); + + return xilinx_core_probe(&conf->core); +} + +static const struct of_device_id xlnx_selectmap_of_match[] = { + { .compatible = "xlnx,fpga-xc7s-selectmap", }, // Spartan-7 + { .compatible = "xlnx,fpga-xc7a-selectmap", }, // Artix-7 + { .compatible = "xlnx,fpga-xc7k-selectmap", }, // Kintex-7 + { .compatible = "xlnx,fpga-xc7v-selectmap", }, // Virtex-7 + {}, +}; +MODULE_DEVICE_TABLE(of, xlnx_selectmap_of_match); + +static struct platform_driver xilinx_selectmap_driver = { + .driver = { + .name = "xilinx-selectmap", + .of_match_table = xlnx_selectmap_of_match, + }, + .probe = xilinx_selectmap_probe, +}; + +module_platform_driver(xilinx_selectmap_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Charles Perry "); +MODULE_DESCRIPTION("Load Xilinx FPGA firmware over SelectMap"); -- cgit v1.3.1