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, 298 insertions, 0 deletions

diff --git a/net/mac802154/trace.h b/net/mac802154/trace.h
new file mode 100644
index 000000000..1574ecc48
--- /dev/null
+++ b/net/mac802154/trace.h
@@ -0,0 +1,298 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Based on net/mac80211/trace.h */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mac802154
+
+#if !defined(__MAC802154_DRIVER_TRACE) || defined(TRACE_HEADER_MULTI_READ)
+#define __MAC802154_DRIVER_TRACE
+
+#include <linux/tracepoint.h>
+
+#include <net/mac802154.h>
+#include "ieee802154_i.h"
+
+#define MAXNAME		32
+#define LOCAL_ENTRY	__array(char, wpan_phy_name, MAXNAME)
+#define LOCAL_ASSIGN	strscpy(__entry->wpan_phy_name, \
+				wpan_phy_name(local->hw.phy), MAXNAME)
+#define LOCAL_PR_FMT	"%s"
+#define LOCAL_PR_ARG	__entry->wpan_phy_name
+
+#define CCA_ENTRY __field(enum nl802154_cca_modes, cca_mode) \
+		  __field(enum nl802154_cca_opts, cca_opt)
+#define CCA_ASSIGN \
+	do {                                     \
+		(__entry->cca_mode) = cca->mode; \
+		(__entry->cca_opt) = cca->opt;   \
+	} while (0)
+#define CCA_PR_FMT "cca_mode: %d, cca_opt: %d"
+#define CCA_PR_ARG __entry->cca_mode, __entry->cca_opt
+
+#define BOOL_TO_STR(bo) (bo) ? "true" : "false"
+
+/* Tracing for driver callbacks */
+
+DECLARE_EVENT_CLASS(local_only_evt4,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+	),
+	TP_printk(LOCAL_PR_FMT, LOCAL_PR_ARG)
+);
+
+DEFINE_EVENT(local_only_evt4, 802154_drv_return_void,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local)
+);
+
+TRACE_EVENT(802154_drv_return_int,
+	TP_PROTO(struct ieee802154_local *local, int ret),
+	TP_ARGS(local, ret),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(int, ret)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->ret = ret;
+	),
+	TP_printk(LOCAL_PR_FMT ", returned: %d", LOCAL_PR_ARG,
+		  __entry->ret)
+);
+
+DEFINE_EVENT(local_only_evt4, 802154_drv_start,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local)
+);
+
+DEFINE_EVENT(local_only_evt4, 802154_drv_stop,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local)
+);
+
+TRACE_EVENT(802154_drv_set_channel,
+	TP_PROTO(struct ieee802154_local *local, u8 page, u8 channel),
+	TP_ARGS(local, page, channel),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(u8, page)
+		__field(u8, channel)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->page = page;
+		__entry->channel = channel;
+	),
+	TP_printk(LOCAL_PR_FMT ", page: %d, channel: %d", LOCAL_PR_ARG,
+		  __entry->page, __entry->channel)
+);
+
+TRACE_EVENT(802154_drv_set_cca_mode,
+	TP_PROTO(struct ieee802154_local *local,
+		 const struct wpan_phy_cca *cca),
+	TP_ARGS(local, cca),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		CCA_ENTRY
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		CCA_ASSIGN;
+	),
+	TP_printk(LOCAL_PR_FMT ", " CCA_PR_FMT, LOCAL_PR_ARG,
+		  CCA_PR_ARG)
+);
+
+TRACE_EVENT(802154_drv_set_cca_ed_level,
+	TP_PROTO(struct ieee802154_local *local, s32 mbm),
+	TP_ARGS(local, mbm),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(s32, mbm)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->mbm = mbm;
+	),
+	TP_printk(LOCAL_PR_FMT ", ed level: %d", LOCAL_PR_ARG,
+		  __entry->mbm)
+);
+
+TRACE_EVENT(802154_drv_set_tx_power,
+	TP_PROTO(struct ieee802154_local *local, s32 power),
+	TP_ARGS(local, power),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(s32, power)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->power = power;
+	),
+	TP_printk(LOCAL_PR_FMT ", mbm: %d", LOCAL_PR_ARG,
+		 __entry->power)
+);
+
+TRACE_EVENT(802154_drv_set_lbt_mode,
+	TP_PROTO(struct ieee802154_local *local, bool mode),
+	TP_ARGS(local, mode),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, mode)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->mode = mode;
+	),
+	TP_printk(LOCAL_PR_FMT ", lbt mode: %s", LOCAL_PR_ARG,
+		  BOOL_TO_STR(__entry->mode))
+);
+
+TRACE_EVENT(802154_drv_set_short_addr,
+	TP_PROTO(struct ieee802154_local *local, __le16 short_addr),
+	TP_ARGS(local, short_addr),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(__le16, short_addr)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->short_addr = short_addr;
+	),
+	TP_printk(LOCAL_PR_FMT ", short addr: 0x%04x", LOCAL_PR_ARG,
+		  le16_to_cpu(__entry->short_addr))
+);
+
+TRACE_EVENT(802154_drv_set_pan_id,
+	TP_PROTO(struct ieee802154_local *local, __le16 pan_id),
+	TP_ARGS(local, pan_id),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(__le16, pan_id)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->pan_id = pan_id;
+	),
+	TP_printk(LOCAL_PR_FMT ", pan id: 0x%04x", LOCAL_PR_ARG,
+		  le16_to_cpu(__entry->pan_id))
+);
+
+TRACE_EVENT(802154_drv_set_extended_addr,
+	TP_PROTO(struct ieee802154_local *local, __le64 extended_addr),
+	TP_ARGS(local, extended_addr),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(__le64, extended_addr)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->extended_addr = extended_addr;
+	),
+	TP_printk(LOCAL_PR_FMT ", extended addr: 0x%llx", LOCAL_PR_ARG,
+		  le64_to_cpu(__entry->extended_addr))
+);
+
+TRACE_EVENT(802154_drv_set_pan_coord,
+	TP_PROTO(struct ieee802154_local *local, bool is_coord),
+	TP_ARGS(local, is_coord),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, is_coord)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->is_coord = is_coord;
+	),
+	TP_printk(LOCAL_PR_FMT ", is_coord: %s", LOCAL_PR_ARG,
+		  BOOL_TO_STR(__entry->is_coord))
+);
+
+TRACE_EVENT(802154_drv_set_csma_params,
+	TP_PROTO(struct ieee802154_local *local, u8 min_be, u8 max_be,
+		 u8 max_csma_backoffs),
+	TP_ARGS(local, min_be, max_be, max_csma_backoffs),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(u8, min_be)
+		__field(u8, max_be)
+		__field(u8, max_csma_backoffs)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN,
+		__entry->min_be = min_be;
+		__entry->max_be = max_be;
+		__entry->max_csma_backoffs = max_csma_backoffs;
+	),
+	TP_printk(LOCAL_PR_FMT ", min be: %d, max be: %d, max csma backoffs: %d",
+		  LOCAL_PR_ARG, __entry->min_be, __entry->max_be,
+		  __entry->max_csma_backoffs)
+);
+
+TRACE_EVENT(802154_drv_set_max_frame_retries,
+	TP_PROTO(struct ieee802154_local *local, s8 max_frame_retries),
+	TP_ARGS(local, max_frame_retries),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(s8, max_frame_retries)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->max_frame_retries = max_frame_retries;
+	),
+	TP_printk(LOCAL_PR_FMT ", max frame retries: %d", LOCAL_PR_ARG,
+		  __entry->max_frame_retries)
+);
+
+TRACE_EVENT(802154_drv_set_promiscuous_mode,
+	TP_PROTO(struct ieee802154_local *local, bool on),
+	TP_ARGS(local, on),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, on)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->on = on;
+	),
+	TP_printk(LOCAL_PR_FMT ", promiscuous mode: %s", LOCAL_PR_ARG,
+		  BOOL_TO_STR(__entry->on))
+);
+
+TRACE_EVENT(802154_new_scan_event,
+	TP_PROTO(struct ieee802154_coord_desc *desc),
+	TP_ARGS(desc),
+	TP_STRUCT__entry(
+		__field(__le16, pan_id)
+		__field(__le64, addr)
+		__field(u8, channel)
+		__field(u8, page)
+	),
+	TP_fast_assign(
+		__entry->page = desc->page;
+		__entry->channel = desc->channel;
+		__entry->pan_id = desc->addr.pan_id;
+		__entry->addr = desc->addr.extended_addr;
+	),
+	TP_printk("panid: %u, coord_addr: 0x%llx, page: %u, channel: %u",
+		  __le16_to_cpu(__entry->pan_id), __le64_to_cpu(__entry->addr),
+		  __entry->page, __entry->channel)
+);
+
+DEFINE_EVENT(802154_new_scan_event, 802154_scan_event,
+	TP_PROTO(struct ieee802154_coord_desc *desc),
+	TP_ARGS(desc)
+);
+
+#endif /* !__MAC802154_DRIVER_TRACE || TRACE_HEADER_MULTI_READ */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace
+#include <trace/define_trace.h>