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

1 files changed, 168 insertions, 0 deletions

diff --git a/drivers/clk/sprd/gate.h b/drivers/clk/sprd/gate.h
new file mode 100644
index 000000000..775519eb1
--- /dev/null
+++ b/drivers/clk/sprd/gate.h
@@ -0,0 +1,168 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+//
+// Spreadtrum gate clock driver
+//
+// Copyright (C) 2017 Spreadtrum, Inc.
+// Author: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
+
+#ifndef _SPRD_GATE_H_
+#define _SPRD_GATE_H_
+
+#include "common.h"
+
+struct sprd_gate {
+	u32			enable_mask;
+	u16			flags;
+	u16			sc_offset;
+	u16			udelay;
+
+	struct sprd_clk_common	common;
+};
+
+/*
+ * sprd_gate->flags is used for:
+ * CLK_GATE_SET_TO_DISABLE	BIT(0)
+ * CLK_GATE_HIWORD_MASK		BIT(1)
+ * CLK_GATE_BIG_ENDIAN		BIT(2)
+ * so we define new flags from	BIT(3)
+ */
+#define SPRD_GATE_NON_AON BIT(3) /* not always powered on, check before read */
+
+#define SPRD_SC_GATE_CLK_HW_INIT_FN(_struct, _name, _parent, _reg,	\
+				    _sc_offset, _enable_mask, _flags,	\
+				    _gate_flags, _udelay, _ops, _fn)	\
+	struct sprd_gate _struct = {					\
+		.enable_mask	= _enable_mask,				\
+		.sc_offset	= _sc_offset,				\
+		.flags		= _gate_flags,				\
+		.udelay		= _udelay,				\
+		.common	= {						\
+			.regmap		= NULL,				\
+			.reg		= _reg,				\
+			.hw.init	= _fn(_name, _parent,		\
+					      _ops, _flags),		\
+		}							\
+	}
+
+#define SPRD_SC_GATE_CLK_OPS_UDELAY(_struct, _name, _parent, _reg,	\
+				    _sc_offset, _enable_mask, _flags,	\
+				    _gate_flags, _udelay, _ops)		\
+	SPRD_SC_GATE_CLK_HW_INIT_FN(_struct, _name, _parent, _reg,	\
+				    _sc_offset, _enable_mask, _flags,	\
+				    _gate_flags, _udelay, _ops, CLK_HW_INIT)
+
+#define SPRD_SC_GATE_CLK_OPS(_struct, _name, _parent, _reg, _sc_offset,	\
+			     _enable_mask, _flags, _gate_flags, _ops)	\
+	SPRD_SC_GATE_CLK_OPS_UDELAY(_struct, _name, _parent, _reg,	\
+				    _sc_offset, _enable_mask, _flags,	\
+				    _gate_flags, 0, _ops)
+
+#define SPRD_SC_GATE_CLK(_struct, _name, _parent, _reg, _sc_offset,	\
+			 _enable_mask, _flags, _gate_flags)		\
+	SPRD_SC_GATE_CLK_OPS(_struct, _name, _parent, _reg, _sc_offset,	\
+			     _enable_mask, _flags, _gate_flags,		\
+			     &sprd_sc_gate_ops)
+
+#define SPRD_GATE_CLK(_struct, _name, _parent, _reg,			\
+		      _enable_mask, _flags, _gate_flags)		\
+	SPRD_SC_GATE_CLK_OPS(_struct, _name, _parent, _reg, 0,		\
+			     _enable_mask, _flags, _gate_flags,		\
+			     &sprd_gate_ops)
+
+#define SPRD_PLL_SC_GATE_CLK(_struct, _name, _parent, _reg, _sc_offset,	\
+			     _enable_mask, _flags, _gate_flags,		\
+			     _udelay)					\
+	SPRD_SC_GATE_CLK_OPS_UDELAY(_struct, _name, _parent, _reg,	\
+				    _sc_offset,	_enable_mask, _flags,	\
+				    _gate_flags, _udelay,		\
+				    &sprd_pll_sc_gate_ops)
+
+
+#define SPRD_SC_GATE_CLK_HW_OPS_UDELAY(_struct, _name, _parent, _reg,	\
+				       _sc_offset, _enable_mask,	\
+				       _flags, _gate_flags,		\
+				       _udelay, _ops)			\
+	SPRD_SC_GATE_CLK_HW_INIT_FN(_struct, _name, _parent, _reg,	\
+				    _sc_offset, _enable_mask, _flags,	\
+				    _gate_flags, _udelay, _ops,		\
+				    CLK_HW_INIT_HW)
+
+#define SPRD_SC_GATE_CLK_HW_OPS(_struct, _name, _parent, _reg,		\
+				_sc_offset, _enable_mask, _flags,	\
+				_gate_flags, _ops)			\
+	SPRD_SC_GATE_CLK_HW_OPS_UDELAY(_struct, _name, _parent, _reg,	\
+				       _sc_offset, _enable_mask,	\
+				       _flags, _gate_flags, 0, _ops)
+
+#define SPRD_SC_GATE_CLK_HW(_struct, _name, _parent, _reg,		\
+			    _sc_offset, _enable_mask, _flags,		\
+			    _gate_flags)				\
+	SPRD_SC_GATE_CLK_HW_OPS(_struct, _name, _parent, _reg,		\
+				_sc_offset, _enable_mask, _flags,	\
+				_gate_flags, &sprd_sc_gate_ops)
+
+#define SPRD_GATE_CLK_HW(_struct, _name, _parent, _reg,			\
+			 _enable_mask, _flags, _gate_flags)		\
+	SPRD_SC_GATE_CLK_HW_OPS(_struct, _name, _parent, _reg, 0,	\
+				_enable_mask, _flags, _gate_flags,	\
+				&sprd_gate_ops)
+
+#define SPRD_PLL_SC_GATE_CLK_HW(_struct, _name, _parent, _reg,		\
+				_sc_offset, _enable_mask, _flags,	\
+				_gate_flags, _udelay)			\
+	SPRD_SC_GATE_CLK_HW_OPS_UDELAY(_struct, _name, _parent, _reg,	\
+				       _sc_offset, _enable_mask,	\
+				       _flags, _gate_flags, _udelay,	\
+				       &sprd_pll_sc_gate_ops)
+
+#define SPRD_SC_GATE_CLK_FW_NAME_OPS_UDELAY(_struct, _name, _parent,	\
+					    _reg, _sc_offset,		\
+					    _enable_mask, _flags,	\
+					    _gate_flags, _udelay, _ops)	\
+	SPRD_SC_GATE_CLK_HW_INIT_FN(_struct, _name, _parent, _reg,	\
+				    _sc_offset, _enable_mask, _flags,	\
+				    _gate_flags, _udelay, _ops,		\
+				    CLK_HW_INIT_FW_NAME)
+
+#define SPRD_SC_GATE_CLK_FW_NAME_OPS(_struct, _name, _parent, _reg,	\
+				     _sc_offset, _enable_mask, _flags,	\
+				     _gate_flags, _ops)			\
+	SPRD_SC_GATE_CLK_FW_NAME_OPS_UDELAY(_struct, _name, _parent,	\
+					    _reg, _sc_offset,		\
+					    _enable_mask, _flags,	\
+					    _gate_flags, 0, _ops)
+
+#define SPRD_SC_GATE_CLK_FW_NAME(_struct, _name, _parent, _reg,		\
+				 _sc_offset, _enable_mask, _flags,	\
+				 _gate_flags)				\
+	SPRD_SC_GATE_CLK_FW_NAME_OPS(_struct, _name, _parent, _reg,	\
+				     _sc_offset, _enable_mask, _flags,	\
+				     _gate_flags, &sprd_sc_gate_ops)
+
+#define SPRD_GATE_CLK_FW_NAME(_struct, _name, _parent, _reg,		\
+			      _enable_mask, _flags, _gate_flags)	\
+	SPRD_SC_GATE_CLK_FW_NAME_OPS(_struct, _name, _parent, _reg, 0,	\
+				     _enable_mask, _flags, _gate_flags,	\
+				     &sprd_gate_ops)
+
+#define SPRD_PLL_SC_GATE_CLK_FW_NAME(_struct, _name, _parent, _reg,	\
+				     _sc_offset, _enable_mask, _flags,	\
+				     _gate_flags, _udelay)		\
+	SPRD_SC_GATE_CLK_FW_NAME_OPS_UDELAY(_struct, _name, _parent,	\
+					    _reg, _sc_offset,		\
+					    _enable_mask, _flags,	\
+					    _gate_flags, _udelay,	\
+					    &sprd_pll_sc_gate_ops)
+
+static inline struct sprd_gate *hw_to_sprd_gate(const struct clk_hw *hw)
+{
+	struct sprd_clk_common *common = hw_to_sprd_clk_common(hw);
+
+	return container_of(common, struct sprd_gate, common);
+}
+
+extern const struct clk_ops sprd_gate_ops;
+extern const struct clk_ops sprd_sc_gate_ops;
+extern const struct clk_ops sprd_pll_sc_gate_ops;
+
+#endif /* _SPRD_GATE_H_ */