sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

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 <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

13 files changed, 390 insertions, 0 deletions

diff --git a/Documentation/features/debug/KASAN/arch-support.txt b/Documentation/features/debug/KASAN/arch-support.txt
new file mode 100644
index 000000000..39c6e78c0
--- /dev/null
+++ b/Documentation/features/debug/KASAN/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          KASAN
+#         Kconfig:       HAVE_ARCH_KASAN
+#         description:   arch supports the KASAN runtime memory checker
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: |  ok  |
+    |         x86: |  ok  |
+    |      xtensa: |  ok  |
+    -----------------------
diff --git a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
new file mode 100644
index 000000000..156687a74
--- /dev/null
+++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          debug-vm-pgtable
+#         Kconfig:       ARCH_HAS_DEBUG_VM_PGTABLE
+#         description:   arch supports pgtable tests for semantics compliance
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: | TODO |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: |  ok  |
+    -----------------------
diff --git a/Documentation/features/debug/gcov-profile-all/arch-support.txt b/Documentation/features/debug/gcov-profile-all/arch-support.txt
new file mode 100644
index 000000000..63494bddc
--- /dev/null
+++ b/Documentation/features/debug/gcov-profile-all/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          gcov-profile-all
+#         Kconfig:       ARCH_HAS_GCOV_PROFILE_ALL
+#         description:   arch supports whole-kernel GCOV code coverage profiling
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: | TODO |
+    |        m68k: | TODO |
+    |  microblaze: |  ok  |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: | TODO |
+    |          um: |  ok  |
+    |         x86: |  ok  |
+    |      xtensa: |  ok  |
+    -----------------------
diff --git a/Documentation/features/debug/kcov/arch-support.txt b/Documentation/features/debug/kcov/arch-support.txt
new file mode 100644
index 000000000..4449e1f55
--- /dev/null
+++ b/Documentation/features/debug/kcov/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          kcov
+#         Kconfig:       ARCH_HAS_KCOV
+#         description:   arch supports kcov for coverage-guided fuzzing
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: |  ok  |
+    |         x86: |  ok  |
+    |      xtensa: |  ok  |
+    -----------------------
diff --git a/Documentation/features/debug/kgdb/arch-support.txt b/Documentation/features/debug/kgdb/arch-support.txt
new file mode 100644
index 000000000..f287f16ce
--- /dev/null
+++ b/Documentation/features/debug/kgdb/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          kgdb
+#         Kconfig:       HAVE_ARCH_KGDB
+#         description:   arch supports the kGDB kernel debugger
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: | TODO |
+    |     hexagon: |  ok  |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: |  ok  |
+    |        mips: |  ok  |
+    |       nios2: |  ok  |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: | TODO |
+    |          sh: |  ok  |
+    |       sparc: |  ok  |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/debug/kmemleak/arch-support.txt b/Documentation/features/debug/kmemleak/arch-support.txt
new file mode 100644
index 000000000..f45149cfa
--- /dev/null
+++ b/Documentation/features/debug/kmemleak/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          kmemleak
+#         Kconfig:       HAVE_DEBUG_KMEMLEAK
+#         description:   arch supports the kernel memory leak detector
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: |  ok  |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: |  ok  |
+    |          um: |  ok  |
+    |         x86: |  ok  |
+    |      xtensa: |  ok  |
+    -----------------------
diff --git a/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt b/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
new file mode 100644
index 000000000..d937b7a03
--- /dev/null
+++ b/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          kprobes-on-ftrace
+#         Kconfig:       HAVE_KPROBES_ON_FTRACE
+#         description:   arch supports combined kprobes and ftrace live patching
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: | TODO |
+    |       arm64: | TODO |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: | TODO |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/debug/kprobes/arch-support.txt b/Documentation/features/debug/kprobes/arch-support.txt
new file mode 100644
index 000000000..1ea27aedd
--- /dev/null
+++ b/Documentation/features/debug/kprobes/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          kprobes
+#         Kconfig:       HAVE_KPROBES
+#         description:   arch supports live patched kernel probe
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: |  ok  |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/debug/kretprobes/arch-support.txt b/Documentation/features/debug/kretprobes/arch-support.txt
new file mode 100644
index 000000000..022be42e6
--- /dev/null
+++ b/Documentation/features/debug/kretprobes/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          kretprobes
+#         Kconfig:       HAVE_KRETPROBES
+#         description:   arch supports kernel function-return probes
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: |  ok  |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: |  ok  |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: |  ok  |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/debug/optprobes/arch-support.txt b/Documentation/features/debug/optprobes/arch-support.txt
new file mode 100644
index 000000000..92f5d0f44
--- /dev/null
+++ b/Documentation/features/debug/optprobes/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          optprobes
+#         Kconfig:       HAVE_OPTPROBES
+#         description:   arch supports live patched optprobes
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: | TODO |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: | TODO |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: | TODO |
+    |        s390: | TODO |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/debug/stackprotector/arch-support.txt b/Documentation/features/debug/stackprotector/arch-support.txt
new file mode 100644
index 000000000..43e49c716
--- /dev/null
+++ b/Documentation/features/debug/stackprotector/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          stackprotector
+#         Kconfig:       HAVE_STACKPROTECTOR
+#         description:   arch supports compiler driven stack overflow protection
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: |  ok  |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: |  ok  |
+    -----------------------
diff --git a/Documentation/features/debug/uprobes/arch-support.txt b/Documentation/features/debug/uprobes/arch-support.txt
new file mode 100644
index 000000000..0c698003c
--- /dev/null
+++ b/Documentation/features/debug/uprobes/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          uprobes
+#         Kconfig:       ARCH_SUPPORTS_UPROBES
+#         description:   arch supports live patched user probes
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: |  ok  |
+    |       arm64: |  ok  |
+    |        csky: |  ok  |
+    |     hexagon: | TODO |
+    |   loongarch: |  ok  |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: |  ok  |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: |  ok  |
+    |       riscv: |  ok  |
+    |        s390: |  ok  |
+    |          sh: | TODO |
+    |       sparc: |  ok  |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------
diff --git a/Documentation/features/debug/user-ret-profiler/arch-support.txt b/Documentation/features/debug/user-ret-profiler/arch-support.txt
new file mode 100644
index 000000000..3e4317675
--- /dev/null
+++ b/Documentation/features/debug/user-ret-profiler/arch-support.txt
@@ -0,0 +1,30 @@
+#
+# Feature name:          user-ret-profiler
+#         Kconfig:       HAVE_USER_RETURN_NOTIFIER
+#         description:   arch supports user-space return from system call profiler
+#
+    -----------------------
+    |         arch |status|
+    -----------------------
+    |       alpha: | TODO |
+    |         arc: | TODO |
+    |         arm: | TODO |
+    |       arm64: | TODO |
+    |        csky: | TODO |
+    |     hexagon: | TODO |
+    |   loongarch: | TODO |
+    |        m68k: | TODO |
+    |  microblaze: | TODO |
+    |        mips: | TODO |
+    |       nios2: | TODO |
+    |    openrisc: | TODO |
+    |      parisc: | TODO |
+    |     powerpc: | TODO |
+    |       riscv: | TODO |
+    |        s390: | TODO |
+    |          sh: | TODO |
+    |       sparc: | TODO |
+    |          um: | TODO |
+    |         x86: |  ok  |
+    |      xtensa: | TODO |
+    -----------------------