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, 253 insertions, 0 deletions

diff --git a/net/bluetooth/hci_codec.c b/net/bluetooth/hci_codec.c
new file mode 100644
index 000000000..7a7e813dc
--- /dev/null
+++ b/net/bluetooth/hci_codec.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (C) 2021 Intel Corporation */
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+#include "hci_codec.h"
+
+static int hci_codec_list_add(struct list_head *list,
+			      struct hci_op_read_local_codec_caps *sent,
+			      struct hci_rp_read_local_codec_caps *rp,
+			      void *caps,
+			      __u32 len)
+{
+	struct codec_list *entry;
+
+	entry = kzalloc(sizeof(*entry) + len, GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->id = sent->id;
+	if (sent->id == 0xFF) {
+		entry->cid = __le16_to_cpu(sent->cid);
+		entry->vid = __le16_to_cpu(sent->vid);
+	}
+	entry->transport = sent->transport;
+	entry->len = len;
+	entry->num_caps = 0;
+	if (rp) {
+		entry->num_caps = rp->num_caps;
+		memcpy(entry->caps, caps, len);
+	}
+	list_add(&entry->list, list);
+
+	return 0;
+}
+
+void hci_codec_list_clear(struct list_head *codec_list)
+{
+	struct codec_list *c, *n;
+
+	list_for_each_entry_safe(c, n, codec_list, list) {
+		list_del(&c->list);
+		kfree(c);
+	}
+}
+
+static void hci_read_codec_capabilities(struct hci_dev *hdev, __u8 transport,
+					struct hci_op_read_local_codec_caps
+					*cmd)
+{
+	__u8 i;
+
+	for (i = 0; i < TRANSPORT_TYPE_MAX; i++) {
+		if (transport & BIT(i)) {
+			struct hci_rp_read_local_codec_caps *rp;
+			struct hci_codec_caps *caps;
+			struct sk_buff *skb;
+			__u8 j;
+			__u32 len;
+
+			cmd->transport = i;
+
+			/* If Read_Codec_Capabilities command is not supported
+			 * then just add codec to the list without caps
+			 */
+			if (!(hdev->commands[45] & 0x08)) {
+				hci_dev_lock(hdev);
+				hci_codec_list_add(&hdev->local_codecs, cmd,
+						   NULL, NULL, 0);
+				hci_dev_unlock(hdev);
+				continue;
+			}
+
+			skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODEC_CAPS,
+						sizeof(*cmd), cmd, 0, HCI_CMD_TIMEOUT, NULL);
+			if (IS_ERR(skb)) {
+				bt_dev_err(hdev, "Failed to read codec capabilities (%ld)",
+					   PTR_ERR(skb));
+				continue;
+			}
+
+			if (skb->len < sizeof(*rp))
+				goto error;
+
+			rp = (void *)skb->data;
+
+			if (rp->status)
+				goto error;
+
+			if (!rp->num_caps) {
+				len = 0;
+				/* this codec doesn't have capabilities */
+				goto skip_caps_parse;
+			}
+
+			skb_pull(skb, sizeof(*rp));
+
+			for (j = 0, len = 0; j < rp->num_caps; j++) {
+				caps = (void *)skb->data;
+				if (skb->len < sizeof(*caps))
+					goto error;
+				if (skb->len < sizeof(caps->len) + caps->len)
+					goto error;
+				len += sizeof(caps->len) + caps->len;
+				skb_pull(skb,  sizeof(caps->len) + caps->len);
+			}
+
+skip_caps_parse:
+			hci_dev_lock(hdev);
+			hci_codec_list_add(&hdev->local_codecs, cmd, rp,
+					   (__u8 *)rp + sizeof(*rp), len);
+			hci_dev_unlock(hdev);
+error:
+			kfree_skb(skb);
+		}
+	}
+}
+
+void hci_read_supported_codecs(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct hci_rp_read_local_supported_codecs *rp;
+	struct hci_std_codecs *std_codecs;
+	struct hci_vnd_codecs *vnd_codecs;
+	struct hci_op_read_local_codec_caps caps;
+	__u8 i;
+
+	skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS, 0, NULL,
+				0, HCI_CMD_TIMEOUT, NULL);
+
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len < sizeof(*rp))
+		goto error;
+
+	rp = (void *)skb->data;
+
+	if (rp->status)
+		goto error;
+
+	skb_pull(skb, sizeof(rp->status));
+
+	std_codecs = skb_pull_data(skb, sizeof(*std_codecs));
+	if (!std_codecs)
+		goto error;
+
+	/* validate codecs length before accessing */
+	if (skb->len < flex_array_size(std_codecs, codec, std_codecs->num))
+		goto error;
+
+	/* enumerate codec capabilities of standard codecs */
+	memset(&caps, 0, sizeof(caps));
+	for (i = 0; i < std_codecs->num; i++) {
+		caps.id = std_codecs->codec[i];
+		caps.direction = 0x00;
+		hci_read_codec_capabilities(hdev,
+					    LOCAL_CODEC_ACL_MASK | LOCAL_CODEC_SCO_MASK, &caps);
+	}
+
+	skb_pull(skb, flex_array_size(std_codecs, codec, std_codecs->num));
+
+	vnd_codecs = skb_pull_data(skb, sizeof(*vnd_codecs));
+	if (!vnd_codecs)
+		goto error;
+
+	/* validate vendor codecs length before accessing */
+	if (skb->len < flex_array_size(vnd_codecs, codec, vnd_codecs->num))
+		goto error;
+
+	/* enumerate vendor codec capabilities */
+	for (i = 0; i < vnd_codecs->num; i++) {
+		caps.id = 0xFF;
+		caps.cid = vnd_codecs->codec[i].cid;
+		caps.vid = vnd_codecs->codec[i].vid;
+		caps.direction = 0x00;
+		hci_read_codec_capabilities(hdev,
+					    LOCAL_CODEC_ACL_MASK | LOCAL_CODEC_SCO_MASK, &caps);
+	}
+
+error:
+	kfree_skb(skb);
+}
+
+void hci_read_supported_codecs_v2(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct hci_rp_read_local_supported_codecs_v2 *rp;
+	struct hci_std_codecs_v2 *std_codecs;
+	struct hci_vnd_codecs_v2 *vnd_codecs;
+	struct hci_op_read_local_codec_caps caps;
+	__u8 i;
+
+	skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS_V2, 0, NULL,
+				0, HCI_CMD_TIMEOUT, NULL);
+
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len < sizeof(*rp))
+		goto error;
+
+	rp = (void *)skb->data;
+
+	if (rp->status)
+		goto error;
+
+	skb_pull(skb, sizeof(rp->status));
+
+	std_codecs = skb_pull_data(skb, sizeof(*std_codecs));
+	if (!std_codecs)
+		goto error;
+
+	/* check for payload data length before accessing */
+	if (skb->len < flex_array_size(std_codecs, codec, std_codecs->num))
+		goto error;
+
+	memset(&caps, 0, sizeof(caps));
+
+	for (i = 0; i < std_codecs->num; i++) {
+		caps.id = std_codecs->codec[i].id;
+		hci_read_codec_capabilities(hdev, std_codecs->codec[i].transport,
+					    &caps);
+	}
+
+	skb_pull(skb, flex_array_size(std_codecs, codec, std_codecs->num));
+
+	vnd_codecs = skb_pull_data(skb, sizeof(*vnd_codecs));
+	if (!vnd_codecs)
+		goto error;
+
+	/* check for payload data length before accessing */
+	if (skb->len < flex_array_size(vnd_codecs, codec, vnd_codecs->num))
+		goto error;
+
+	for (i = 0; i < vnd_codecs->num; i++) {
+		caps.id = 0xFF;
+		caps.cid = vnd_codecs->codec[i].cid;
+		caps.vid = vnd_codecs->codec[i].vid;
+		hci_read_codec_capabilities(hdev, vnd_codecs->codec[i].transport,
+					    &caps);
+	}
+
+error:
+	kfree_skb(skb);
+}