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/arc/axs101.txt | 7 +++++ Documentation/devicetree/bindings/arc/axs103.txt | 8 ++++++ Documentation/devicetree/bindings/arc/eznps.txt | 7 +++++ Documentation/devicetree/bindings/arc/hsdk.txt | 7 +++++ Documentation/devicetree/bindings/arc/pct.txt | 20 +++++++++++++ .../devicetree/bindings/arc/snps,archs-pct.yaml | 33 ++++++++++++++++++++++ 6 files changed, 82 insertions(+) create mode 100644 Documentation/devicetree/bindings/arc/axs101.txt create mode 100644 Documentation/devicetree/bindings/arc/axs103.txt create mode 100644 Documentation/devicetree/bindings/arc/eznps.txt create mode 100644 Documentation/devicetree/bindings/arc/hsdk.txt create mode 100644 Documentation/devicetree/bindings/arc/pct.txt create mode 100644 Documentation/devicetree/bindings/arc/snps,archs-pct.yaml (limited to 'Documentation/devicetree/bindings/arc') diff --git a/Documentation/devicetree/bindings/arc/axs101.txt b/Documentation/devicetree/bindings/arc/axs101.txt new file mode 100644 index 000000000..48290d517 --- /dev/null +++ b/Documentation/devicetree/bindings/arc/axs101.txt @@ -0,0 +1,7 @@ +Synopsys DesignWare ARC Software Development Platforms Device Tree Bindings +--------------------------------------------------------------------------- + +SDP Main Board with an AXC001 CPU Card hoisting ARC700 core in silicon + +Required root node properties: + - compatible = "snps,axs101", "snps,arc-sdp"; diff --git a/Documentation/devicetree/bindings/arc/axs103.txt b/Documentation/devicetree/bindings/arc/axs103.txt new file mode 100644 index 000000000..6eea862e7 --- /dev/null +++ b/Documentation/devicetree/bindings/arc/axs103.txt @@ -0,0 +1,8 @@ +Synopsys DesignWare ARC Software Development Platforms Device Tree Bindings +--------------------------------------------------------------------------- + +SDP Main Board with an AXC003 FPGA Card which can contain various flavours of +HS38x cores. + +Required root node properties: + - compatible = "snps,axs103", "snps,arc-sdp"; diff --git a/Documentation/devicetree/bindings/arc/eznps.txt b/Documentation/devicetree/bindings/arc/eznps.txt new file mode 100644 index 000000000..1aa50c640 --- /dev/null +++ b/Documentation/devicetree/bindings/arc/eznps.txt @@ -0,0 +1,7 @@ +EZchip NPS Network Processor Platforms Device Tree Bindings +--------------------------------------------------------------------------- + +Appliance main board with NPS400 ASIC. + +Required root node properties: + - compatible = "ezchip,arc-nps"; diff --git a/Documentation/devicetree/bindings/arc/hsdk.txt b/Documentation/devicetree/bindings/arc/hsdk.txt new file mode 100644 index 000000000..be50654bb --- /dev/null +++ b/Documentation/devicetree/bindings/arc/hsdk.txt @@ -0,0 +1,7 @@ +Synopsys DesignWare ARC HS Development Kit Device Tree Bindings +--------------------------------------------------------------------------- + +ARC HSDK Board with quad-core ARC HS38x4 in silicon. + +Required root node properties: + - compatible = "snps,hsdk"; diff --git a/Documentation/devicetree/bindings/arc/pct.txt b/Documentation/devicetree/bindings/arc/pct.txt new file mode 100644 index 000000000..4e874d9a3 --- /dev/null +++ b/Documentation/devicetree/bindings/arc/pct.txt @@ -0,0 +1,20 @@ +* ARC Performance Counters + +The ARC700 can be configured with a pipeline performance monitor for counting +CPU and cache events like cache misses and hits. Like conventional PCT there +are 100+ hardware conditions dynamically mapped to up to 32 counters + +Note that: + * The ARC 700 PCT does not support interrupts; although HW events may be + counted, the HW events themselves cannot serve as a trigger for a sample. + +Required properties: + +- compatible : should contain + "snps,arc700-pct" + +Example: + +pmu { + compatible = "snps,arc700-pct"; +}; diff --git a/Documentation/devicetree/bindings/arc/snps,archs-pct.yaml b/Documentation/devicetree/bindings/arc/snps,archs-pct.yaml new file mode 100644 index 000000000..532f7584f --- /dev/null +++ b/Documentation/devicetree/bindings/arc/snps,archs-pct.yaml @@ -0,0 +1,33 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/arc/snps,archs-pct.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: ARC HS Performance Counters + +maintainers: + - Aryabhatta Dey + +description: + The ARC HS can be configured with a pipeline performance monitor for counting + CPU and cache events like cache misses and hits. Like conventional PCT there + are 100+ hardware conditions dynamically mapped to up to 32 counters. + It also supports overflow interrupts. + +properties: + compatible: + const: snps,archs-pct + + reg: + maxItems: 1 + + clocks: + maxItems: 1 + +required: + - compatible + - reg + - clocks + +additionalProperties: false -- cgit v1.3.1