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, 128 insertions, 0 deletions

diff --git a/net/ethtool/cmis.h b/net/ethtool/cmis.h
new file mode 100644
index 000000000..778783a0f
--- /dev/null
+++ b/net/ethtool/cmis.h
@@ -0,0 +1,128 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#define ETHTOOL_CMIS_CDB_LPL_MAX_PL_LENGTH		120
+#define ETHTOOL_CMIS_CDB_EPL_MAX_PL_LENGTH		2048
+#define ETHTOOL_CMIS_CDB_CMD_PAGE			0x9F
+#define ETHTOOL_CMIS_CDB_PAGE_I2C_ADDR			0x50
+
+/**
+ * struct ethtool_cmis_cdb - CDB commands parameters
+ * @cmis_rev: CMIS revision major.
+ * @read_write_len_ext: Allowable additional number of byte octets to the LPL
+ *			in a READ or a WRITE CDB commands.
+ * @max_completion_time:  Maximum CDB command completion time in msec.
+ */
+struct ethtool_cmis_cdb {
+	u8	cmis_rev;
+	u8      read_write_len_ext;
+	u16     max_completion_time;
+};
+
+enum ethtool_cmis_cdb_cmd_id {
+	ETHTOOL_CMIS_CDB_CMD_QUERY_STATUS		= 0x0000,
+	ETHTOOL_CMIS_CDB_CMD_MODULE_FEATURES		= 0x0040,
+	ETHTOOL_CMIS_CDB_CMD_FW_MANAGMENT_FEATURES	= 0x0041,
+	ETHTOOL_CMIS_CDB_CMD_START_FW_DOWNLOAD		= 0x0101,
+	ETHTOOL_CMIS_CDB_CMD_WRITE_FW_BLOCK_LPL		= 0x0103,
+	ETHTOOL_CMIS_CDB_CMD_WRITE_FW_BLOCK_EPL		= 0x0104,
+	ETHTOOL_CMIS_CDB_CMD_COMPLETE_FW_DOWNLOAD	= 0x0107,
+	ETHTOOL_CMIS_CDB_CMD_RUN_FW_IMAGE		= 0x0109,
+	ETHTOOL_CMIS_CDB_CMD_COMMIT_FW_IMAGE		= 0x010A,
+};
+
+/**
+ * struct ethtool_cmis_cdb_request - CDB commands request fields as decribed in
+ *				the CMIS standard
+ * @id: Command ID.
+ * @epl_len: EPL memory length.
+ * @lpl_len: LPL memory length.
+ * @chk_code: Check code for the previous field and the payload.
+ * @resv1: Added to match the CMIS standard request continuity.
+ * @resv2: Added to match the CMIS standard request continuity.
+ * @payload: Payload for the CDB commands.
+ * @epl: Extended payload for the CDB commands.
+ */
+struct ethtool_cmis_cdb_request {
+	__be16 id;
+	struct_group(body,
+		__be16 epl_len;
+		u8 lpl_len;
+		u8 chk_code;
+		u8 resv1;
+		u8 resv2;
+		u8 payload[ETHTOOL_CMIS_CDB_LPL_MAX_PL_LENGTH];
+	);
+	u8 *epl;	/* Everything above this field checksummed. */
+};
+
+#define CDB_F_COMPLETION_VALID		BIT(0)
+#define CDB_F_STATUS_VALID		BIT(1)
+#define CDB_F_MODULE_STATE_VALID	BIT(2)
+
+/**
+ * struct ethtool_cmis_cdb_cmd_args - CDB commands execution arguments
+ * @req: CDB command fields as described in the CMIS standard.
+ * @max_duration: Maximum duration time for command completion in msec.
+ * @msleep_pre_rpl: Waiting time before checking reply in msec.
+ * @read_write_len_ext: Allowable additional number of byte octets to the LPL
+ *			in a READ or a WRITE commands.
+ * @rpl_exp_len: Expected reply length in bytes.
+ * @flags: Validation flags for CDB commands.
+ * @err_msg: Error message to be sent to user space.
+ */
+struct ethtool_cmis_cdb_cmd_args {
+	struct ethtool_cmis_cdb_request req;
+	u16				max_duration;
+	u16				msleep_pre_rpl;
+	u8				read_write_len_ext;
+	u8                              rpl_exp_len;
+	u8				flags;
+	char				*err_msg;
+};
+
+/**
+ * struct ethtool_cmis_cdb_rpl_hdr - CDB commands reply header arguments
+ * @rpl_len: Reply length.
+ * @rpl_chk_code: Reply check code.
+ */
+struct ethtool_cmis_cdb_rpl_hdr {
+	u8 rpl_len;
+	u8 rpl_chk_code;
+};
+
+/**
+ * struct ethtool_cmis_cdb_rpl - CDB commands reply arguments
+ * @hdr: CDB commands reply header arguments.
+ * @payload: Payload for the CDB commands reply.
+ */
+struct ethtool_cmis_cdb_rpl {
+	struct ethtool_cmis_cdb_rpl_hdr hdr;
+	u8 payload[ETHTOOL_CMIS_CDB_LPL_MAX_PL_LENGTH];
+};
+
+u32 ethtool_cmis_get_max_lpl_size(u8 num_of_byte_octs);
+
+void ethtool_cmis_cdb_compose_args(struct ethtool_cmis_cdb_cmd_args *args,
+				   enum ethtool_cmis_cdb_cmd_id cmd, u8 *lpl,
+				   u8 lpl_len, u8 *epl, u16 epl_len,
+				   u16 max_duration, u8 read_write_len_ext,
+				   u16 msleep_pre_rpl, u8 rpl_exp_len,
+				   u8 flags);
+
+void ethtool_cmis_cdb_check_completion_flag(u8 cmis_rev, u8 *flags);
+
+void ethtool_cmis_page_init(struct ethtool_module_eeprom *page_data,
+			    u8 page, u32 offset, u32 length);
+
+struct ethtool_cmis_cdb *
+ethtool_cmis_cdb_init(struct net_device *dev,
+		      const struct ethtool_module_fw_flash_params *params,
+		      struct ethnl_module_fw_flash_ntf_params *ntf_params);
+void ethtool_cmis_cdb_fini(struct ethtool_cmis_cdb *cdb);
+
+int ethtool_cmis_wait_for_cond(struct net_device *dev, u8 flags, u8 flag,
+			       u16 max_duration, u32 offset,
+			       bool (*cond_success)(u8), bool (*cond_fail)(u8), u8 *state);
+
+int ethtool_cmis_cdb_execute_cmd(struct net_device *dev,
+				 struct ethtool_cmis_cdb_cmd_args *args);