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/firmware/google/Kconfig | 85 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 drivers/firmware/google/Kconfig (limited to 'drivers/firmware/google/Kconfig') diff --git a/drivers/firmware/google/Kconfig b/drivers/firmware/google/Kconfig new file mode 100644 index 000000000..b78c644fa --- /dev/null +++ b/drivers/firmware/google/Kconfig @@ -0,0 +1,85 @@ +# SPDX-License-Identifier: GPL-2.0-only +menuconfig GOOGLE_FIRMWARE + bool "Google Firmware Drivers" + default n + help + These firmware drivers are used by Google servers, + Chromebooks and other devices using coreboot firmware. + If in doubt, say "N". + +if GOOGLE_FIRMWARE + +config GOOGLE_SMI + tristate "SMI interface for Google platforms" + depends on X86 && ACPI && DMI + help + Say Y here if you want to enable SMI callbacks for Google + platforms. This provides an interface for writing to and + clearing the event log. If CONFIG_EFI is also enabled this + driver provides an interface for reading and writing NVRAM + variables. + +config GOOGLE_CBMEM + tristate "CBMEM entries in sysfs" + depends on GOOGLE_COREBOOT_TABLE + help + CBMEM is a downwards-growing memory region created by the + Coreboot BIOS containing tagged data structures from the + BIOS. These data structures expose things like the verified + boot firmware variables, flash layout, firmware event log, + and more. + + This option enables the cbmem module, which causes the + kernel to search for Coreboot CBMEM entries, and expose the + memory for each entry in sysfs under + /sys/bus/coreboot/devices/cbmem-. + +config GOOGLE_COREBOOT_TABLE + tristate "Coreboot Table Access" + depends on HAS_IOMEM && (ACPI || OF) + help + This option enables the coreboot_table module, which provides other + firmware modules access to the coreboot table. The coreboot table + pointer is accessed through the ACPI "GOOGCB00" object or the + device tree node /firmware/coreboot. + If unsure say N. + +config GOOGLE_MEMCONSOLE + tristate + depends on GOOGLE_MEMCONSOLE_X86_LEGACY || GOOGLE_MEMCONSOLE_COREBOOT + +config GOOGLE_MEMCONSOLE_X86_LEGACY + tristate "Firmware Memory Console - X86 Legacy support" + depends on X86 && ACPI && DMI + select GOOGLE_MEMCONSOLE + help + This option enables the kernel to search for a firmware log in + the EBDA on Google servers. If found, this log is exported to + userland in the file /sys/firmware/log. + +config GOOGLE_FRAMEBUFFER_COREBOOT + tristate "Coreboot Framebuffer" + depends on GOOGLE_COREBOOT_TABLE + help + This option enables the kernel to search for a framebuffer in + the coreboot table. If found, it is registered with a platform + device of type coreboot-framebuffer. Using the old device of + type simple-framebuffer is deprecated. + +config GOOGLE_MEMCONSOLE_COREBOOT + tristate "Firmware Memory Console" + depends on GOOGLE_COREBOOT_TABLE + select GOOGLE_MEMCONSOLE + help + This option enables the kernel to search for a firmware log in + the coreboot table. If found, this log is exported to userland + in the file /sys/firmware/log. + +config GOOGLE_VPD + tristate "Vital Product Data" + depends on GOOGLE_COREBOOT_TABLE + help + This option enables the kernel to expose the content of Google VPD + under /sys/firmware/vpd. + +endif # GOOGLE_FIRMWARE -- cgit v1.3.1