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, 229 insertions, 0 deletions

diff --git a/drivers/media/rc/ir-jvc-decoder.c b/drivers/media/rc/ir-jvc-decoder.c
new file mode 100644
index 000000000..8b10954d2
--- /dev/null
+++ b/drivers/media/rc/ir-jvc-decoder.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* ir-jvc-decoder.c - handle JVC IR Pulse/Space protocol
+ *
+ * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
+ */
+
+#include <linux/bitrev.h>
+#include <linux/module.h>
+#include "rc-core-priv.h"
+
+#define JVC_NBITS		16		/* dev(8) + func(8) */
+#define JVC_UNIT		525		/* us */
+#define JVC_HEADER_PULSE	(16 * JVC_UNIT) /* lack of header -> repeat */
+#define JVC_HEADER_SPACE	(8  * JVC_UNIT)
+#define JVC_BIT_PULSE		(1  * JVC_UNIT)
+#define JVC_BIT_0_SPACE		(1  * JVC_UNIT)
+#define JVC_BIT_1_SPACE		(3  * JVC_UNIT)
+#define JVC_TRAILER_PULSE	(1  * JVC_UNIT)
+#define	JVC_TRAILER_SPACE	(35 * JVC_UNIT)
+
+enum jvc_state {
+	STATE_INACTIVE,
+	STATE_HEADER_SPACE,
+	STATE_BIT_PULSE,
+	STATE_BIT_SPACE,
+	STATE_TRAILER_PULSE,
+	STATE_TRAILER_SPACE,
+	STATE_CHECK_REPEAT,
+};
+
+/**
+ * ir_jvc_decode() - Decode one JVC pulse or space
+ * @dev:	the struct rc_dev descriptor of the device
+ * @ev:   the struct ir_raw_event descriptor of the pulse/space
+ *
+ * This function returns -EINVAL if the pulse violates the state machine
+ */
+static int ir_jvc_decode(struct rc_dev *dev, struct ir_raw_event ev)
+{
+	struct jvc_dec *data = &dev->raw->jvc;
+
+	if (!is_timing_event(ev)) {
+		if (ev.overflow)
+			data->state = STATE_INACTIVE;
+		return 0;
+	}
+
+	if (!geq_margin(ev.duration, JVC_UNIT, JVC_UNIT / 2))
+		goto out;
+
+	dev_dbg(&dev->dev, "JVC decode started at state %d (%uus %s)\n",
+		data->state, ev.duration, TO_STR(ev.pulse));
+
+again:
+	switch (data->state) {
+
+	case STATE_INACTIVE:
+		if (!ev.pulse)
+			break;
+
+		if (!eq_margin(ev.duration, JVC_HEADER_PULSE, JVC_UNIT / 2))
+			break;
+
+		data->count = 0;
+		data->first = true;
+		data->toggle = !data->toggle;
+		data->state = STATE_HEADER_SPACE;
+		return 0;
+
+	case STATE_HEADER_SPACE:
+		if (ev.pulse)
+			break;
+
+		if (!eq_margin(ev.duration, JVC_HEADER_SPACE, JVC_UNIT / 2))
+			break;
+
+		data->state = STATE_BIT_PULSE;
+		return 0;
+
+	case STATE_BIT_PULSE:
+		if (!ev.pulse)
+			break;
+
+		if (!eq_margin(ev.duration, JVC_BIT_PULSE, JVC_UNIT / 2))
+			break;
+
+		data->state = STATE_BIT_SPACE;
+		return 0;
+
+	case STATE_BIT_SPACE:
+		if (ev.pulse)
+			break;
+
+		data->bits <<= 1;
+		if (eq_margin(ev.duration, JVC_BIT_1_SPACE, JVC_UNIT / 2)) {
+			data->bits |= 1;
+			decrease_duration(&ev, JVC_BIT_1_SPACE);
+		} else if (eq_margin(ev.duration, JVC_BIT_0_SPACE, JVC_UNIT / 2))
+			decrease_duration(&ev, JVC_BIT_0_SPACE);
+		else
+			break;
+		data->count++;
+
+		if (data->count == JVC_NBITS)
+			data->state = STATE_TRAILER_PULSE;
+		else
+			data->state = STATE_BIT_PULSE;
+		return 0;
+
+	case STATE_TRAILER_PULSE:
+		if (!ev.pulse)
+			break;
+
+		if (!eq_margin(ev.duration, JVC_TRAILER_PULSE, JVC_UNIT / 2))
+			break;
+
+		data->state = STATE_TRAILER_SPACE;
+		return 0;
+
+	case STATE_TRAILER_SPACE:
+		if (ev.pulse)
+			break;
+
+		if (!geq_margin(ev.duration, JVC_TRAILER_SPACE, JVC_UNIT / 2))
+			break;
+
+		if (data->first) {
+			u32 scancode;
+			scancode = (bitrev8((data->bits >> 8) & 0xff) << 8) |
+				   (bitrev8((data->bits >> 0) & 0xff) << 0);
+			dev_dbg(&dev->dev, "JVC scancode 0x%04x\n", scancode);
+			rc_keydown(dev, RC_PROTO_JVC, scancode, data->toggle);
+			data->first = false;
+			data->old_bits = data->bits;
+		} else if (data->bits == data->old_bits) {
+			dev_dbg(&dev->dev, "JVC repeat\n");
+			rc_repeat(dev);
+		} else {
+			dev_dbg(&dev->dev, "JVC invalid repeat msg\n");
+			break;
+		}
+
+		data->count = 0;
+		data->state = STATE_CHECK_REPEAT;
+		return 0;
+
+	case STATE_CHECK_REPEAT:
+		if (!ev.pulse)
+			break;
+
+		if (eq_margin(ev.duration, JVC_HEADER_PULSE, JVC_UNIT / 2))
+			data->state = STATE_INACTIVE;
+  else
+			data->state = STATE_BIT_PULSE;
+		goto again;
+	}
+
+out:
+	dev_dbg(&dev->dev, "JVC decode failed at state %d (%uus %s)\n",
+		data->state, ev.duration, TO_STR(ev.pulse));
+	data->state = STATE_INACTIVE;
+	return -EINVAL;
+}
+
+static const struct ir_raw_timings_pd ir_jvc_timings = {
+	.header_pulse  = JVC_HEADER_PULSE,
+	.header_space  = JVC_HEADER_SPACE,
+	.bit_pulse     = JVC_BIT_PULSE,
+	.bit_space[0]  = JVC_BIT_0_SPACE,
+	.bit_space[1]  = JVC_BIT_1_SPACE,
+	.trailer_pulse = JVC_TRAILER_PULSE,
+	.trailer_space = JVC_TRAILER_SPACE,
+	.msb_first     = 1,
+};
+
+/**
+ * ir_jvc_encode() - Encode a scancode as a stream of raw events
+ *
+ * @protocol:	protocol to encode
+ * @scancode:	scancode to encode
+ * @events:	array of raw ir events to write into
+ * @max:	maximum size of @events
+ *
+ * Returns:	The number of events written.
+ *		-ENOBUFS if there isn't enough space in the array to fit the
+ *		encoding. In this case all @max events will have been written.
+ */
+static int ir_jvc_encode(enum rc_proto protocol, u32 scancode,
+			 struct ir_raw_event *events, unsigned int max)
+{
+	struct ir_raw_event *e = events;
+	int ret;
+	u32 raw = (bitrev8((scancode >> 8) & 0xff) << 8) |
+		  (bitrev8((scancode >> 0) & 0xff) << 0);
+
+	ret = ir_raw_gen_pd(&e, max, &ir_jvc_timings, JVC_NBITS, raw);
+	if (ret < 0)
+		return ret;
+
+	return e - events;
+}
+
+static struct ir_raw_handler jvc_handler = {
+	.protocols	= RC_PROTO_BIT_JVC,
+	.decode		= ir_jvc_decode,
+	.encode		= ir_jvc_encode,
+	.carrier	= 38000,
+	.min_timeout	= JVC_TRAILER_SPACE,
+};
+
+static int __init ir_jvc_decode_init(void)
+{
+	ir_raw_handler_register(&jvc_handler);
+
+	printk(KERN_INFO "IR JVC protocol handler initialized\n");
+	return 0;
+}
+
+static void __exit ir_jvc_decode_exit(void)
+{
+	ir_raw_handler_unregister(&jvc_handler);
+}
+
+module_init(ir_jvc_decode_init);
+module_exit(ir_jvc_decode_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
+MODULE_DESCRIPTION("JVC IR protocol decoder");