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 --- Documentation/devicetree/bindings/csky/cpus.txt | 73 +++++++++++++++++++++++++ Documentation/devicetree/bindings/csky/pmu.txt | 38 +++++++++++++ 2 files changed, 111 insertions(+) create mode 100644 Documentation/devicetree/bindings/csky/cpus.txt create mode 100644 Documentation/devicetree/bindings/csky/pmu.txt (limited to 'Documentation/devicetree/bindings/csky') diff --git a/Documentation/devicetree/bindings/csky/cpus.txt b/Documentation/devicetree/bindings/csky/cpus.txt new file mode 100644 index 000000000..ae79412f2 --- /dev/null +++ b/Documentation/devicetree/bindings/csky/cpus.txt @@ -0,0 +1,73 @@ +================== +C-SKY CPU Bindings +================== + +The device tree allows to describe the layout of CPUs in a system through +the "cpus" node, which in turn contains a number of subnodes (ie "cpu") +defining properties for every cpu. + +Only SMP system need to care about the cpus node and single processor +needn't define cpus node at all. + +===================================== +cpus and cpu node bindings definition +===================================== + +- cpus node + + Description: Container of cpu nodes + + The node name must be "cpus". + + A cpus node must define the following properties: + + - #address-cells + Usage: required + Value type: + Definition: must be set to 1 + - #size-cells + Usage: required + Value type: + Definition: must be set to 0 + +- cpu node + + Description: Describes one of SMP cores + + PROPERTIES + + - device_type + Usage: required + Value type: + Definition: must be "cpu" + - reg + Usage: required + Value type: + Definition: CPU index + - compatible: + Usage: required + Value type: + Definition: must contain "csky", eg: + "csky,610" + "csky,807" + "csky,810" + "csky,860" + +Example: +-------- + + cpus { + #address-cells = <1>; + #size-cells = <0>; + cpu@0 { + device_type = "cpu"; + reg = <0>; + status = "ok"; + }; + + cpu@1 { + device_type = "cpu"; + reg = <1>; + status = "ok"; + }; + }; diff --git a/Documentation/devicetree/bindings/csky/pmu.txt b/Documentation/devicetree/bindings/csky/pmu.txt new file mode 100644 index 000000000..728d05ca6 --- /dev/null +++ b/Documentation/devicetree/bindings/csky/pmu.txt @@ -0,0 +1,38 @@ +=============================== +C-SKY Performance Monitor Units +=============================== + +C-SKY Performance Monitor is designed for ck807/ck810/ck860 SMP soc and +it could count cpu's events for helping analysis performance issues. + +============================ +PMU node bindings definition +============================ + + Description: Describes PMU + + PROPERTIES + + - compatible + Usage: required + Value type: + Definition: must be "csky,csky-pmu" + - interrupts + Usage: required + Value type: + Definition: must be pmu irq num defined by soc + - count-width + Usage: optional + Value type: + Definition: the width of pmu counter + +Examples: +--------- +#include + + pmu: performace-monitor { + compatible = "csky,csky-pmu"; + interrupts = <23 IRQ_TYPE_EDGE_RISING>; + interrupt-parent = <&intc>; + count-width = <48>; + }; -- cgit v1.3.1