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, 210 insertions, 0 deletions

diff --git a/net/bluetooth/aosp.c b/net/bluetooth/aosp.c
new file mode 100644
index 000000000..59025771a
--- /dev/null
+++ b/net/bluetooth/aosp.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Intel Corporation
+ */
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+
+#include "aosp.h"
+
+/* Command complete parameters of LE_Get_Vendor_Capabilities_Command
+ * The parameters grow over time. The base version that declares the
+ * version_supported field is v0.95. Refer to
+ * https://cs.android.com/android/platform/superproject/+/master:system/
+ *         bt/gd/hci/controller.cc;l=452?q=le_get_vendor_capabilities_handler
+ */
+struct aosp_rp_le_get_vendor_capa {
+	/* v0.95: 15 octets */
+	__u8	status;
+	__u8	max_advt_instances;
+	__u8	offloaded_resolution_of_private_address;
+	__le16	total_scan_results_storage;
+	__u8	max_irk_list_sz;
+	__u8	filtering_support;
+	__u8	max_filter;
+	__u8	activity_energy_info_support;
+	__le16	version_supported;
+	__le16	total_num_of_advt_tracked;
+	__u8	extended_scan_support;
+	__u8	debug_logging_supported;
+	/* v0.96: 16 octets */
+	__u8	le_address_generation_offloading_support;
+	/* v0.98: 21 octets */
+	__le32	a2dp_source_offload_capability_mask;
+	__u8	bluetooth_quality_report_support;
+	/* v1.00: 25 octets */
+	__le32	dynamic_audio_buffer_support;
+} __packed;
+
+#define VENDOR_CAPA_BASE_SIZE		15
+#define VENDOR_CAPA_0_98_SIZE		21
+
+void aosp_do_open(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct aosp_rp_le_get_vendor_capa *rp;
+	u16 version_supported;
+
+	if (!hdev->aosp_capable)
+		return;
+
+	bt_dev_dbg(hdev, "Initialize AOSP extension");
+
+	/* LE Get Vendor Capabilities Command */
+	skb = __hci_cmd_sync(hdev, hci_opcode_pack(0x3f, 0x153), 0, NULL,
+			     HCI_CMD_TIMEOUT);
+	if (IS_ERR_OR_NULL(skb)) {
+		if (!skb)
+			skb = ERR_PTR(-EIO);
+
+		bt_dev_err(hdev, "AOSP get vendor capabilities (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	/* A basic length check */
+	if (skb->len < VENDOR_CAPA_BASE_SIZE)
+		goto length_error;
+
+	rp = (struct aosp_rp_le_get_vendor_capa *)skb->data;
+
+	version_supported = le16_to_cpu(rp->version_supported);
+	/* AOSP displays the version number like v0.98, v1.00, etc. */
+	bt_dev_info(hdev, "AOSP extensions version v%u.%02u",
+		    version_supported >> 8, version_supported & 0xff);
+
+	/* Do not support very old versions. */
+	if (version_supported < 95) {
+		bt_dev_warn(hdev, "AOSP capabilities version %u too old",
+			    version_supported);
+		goto done;
+	}
+
+	if (version_supported < 98) {
+		bt_dev_warn(hdev, "AOSP quality report is not supported");
+		goto done;
+	}
+
+	if (skb->len < VENDOR_CAPA_0_98_SIZE)
+		goto length_error;
+
+	/* The bluetooth_quality_report_support is defined at version
+	 * v0.98. Refer to
+	 * https://cs.android.com/android/platform/superproject/+/
+	 *         master:system/bt/gd/hci/controller.cc;l=477
+	 */
+	if (rp->bluetooth_quality_report_support) {
+		hdev->aosp_quality_report = true;
+		bt_dev_info(hdev, "AOSP quality report is supported");
+	}
+
+	goto done;
+
+length_error:
+	bt_dev_err(hdev, "AOSP capabilities length %d too short", skb->len);
+
+done:
+	kfree_skb(skb);
+}
+
+void aosp_do_close(struct hci_dev *hdev)
+{
+	if (!hdev->aosp_capable)
+		return;
+
+	bt_dev_dbg(hdev, "Cleanup of AOSP extension");
+}
+
+/* BQR command */
+#define BQR_OPCODE			hci_opcode_pack(0x3f, 0x015e)
+
+/* BQR report action */
+#define REPORT_ACTION_ADD		0x00
+#define REPORT_ACTION_DELETE		0x01
+#define REPORT_ACTION_CLEAR		0x02
+
+/* BQR event masks */
+#define QUALITY_MONITORING		BIT(0)
+#define APPRAOCHING_LSTO		BIT(1)
+#define A2DP_AUDIO_CHOPPY		BIT(2)
+#define SCO_VOICE_CHOPPY		BIT(3)
+
+#define DEFAULT_BQR_EVENT_MASK	(QUALITY_MONITORING | APPRAOCHING_LSTO | \
+				 A2DP_AUDIO_CHOPPY | SCO_VOICE_CHOPPY)
+
+/* Reporting at milliseconds so as not to stress the controller too much.
+ * Range: 0 ~ 65535 ms
+ */
+#define DEFALUT_REPORT_INTERVAL_MS	5000
+
+struct aosp_bqr_cp {
+	__u8	report_action;
+	__u32	event_mask;
+	__u16	min_report_interval;
+} __packed;
+
+static int enable_quality_report(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct aosp_bqr_cp cp;
+
+	cp.report_action = REPORT_ACTION_ADD;
+	cp.event_mask = DEFAULT_BQR_EVENT_MASK;
+	cp.min_report_interval = DEFALUT_REPORT_INTERVAL_MS;
+
+	skb = __hci_cmd_sync(hdev, BQR_OPCODE, sizeof(cp), &cp,
+			     HCI_CMD_TIMEOUT);
+	if (IS_ERR_OR_NULL(skb)) {
+		if (!skb)
+			skb = ERR_PTR(-EIO);
+
+		bt_dev_err(hdev, "Enabling Android BQR failed (%ld)",
+			   PTR_ERR(skb));
+		return PTR_ERR(skb);
+	}
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static int disable_quality_report(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct aosp_bqr_cp cp = { 0 };
+
+	cp.report_action = REPORT_ACTION_CLEAR;
+
+	skb = __hci_cmd_sync(hdev, BQR_OPCODE, sizeof(cp), &cp,
+			     HCI_CMD_TIMEOUT);
+	if (IS_ERR_OR_NULL(skb)) {
+		if (!skb)
+			skb = ERR_PTR(-EIO);
+
+		bt_dev_err(hdev, "Disabling Android BQR failed (%ld)",
+			   PTR_ERR(skb));
+		return PTR_ERR(skb);
+	}
+
+	kfree_skb(skb);
+	return 0;
+}
+
+bool aosp_has_quality_report(struct hci_dev *hdev)
+{
+	return hdev->aosp_quality_report;
+}
+
+int aosp_set_quality_report(struct hci_dev *hdev, bool enable)
+{
+	if (!aosp_has_quality_report(hdev))
+		return -EOPNOTSUPP;
+
+	bt_dev_dbg(hdev, "quality report enable %d", enable);
+
+	/* Enable or disable the quality report feature. */
+	if (enable)
+		return enable_quality_report(hdev);
+	else
+		return disable_quality_report(hdev);
+}