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, 387 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/debug.h b/drivers/mtd/ubi/debug.h
new file mode 100644
index 000000000..b2fd97548
--- /dev/null
+++ b/drivers/mtd/ubi/debug.h
@@ -0,0 +1,387 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) International Business Machines Corp., 2006
+ *
+ * Author: Artem Bityutskiy (Битюцкий Артём)
+ */
+
+#ifndef __UBI_DEBUG_H__
+#define __UBI_DEBUG_H__
+
+void ubi_dump_flash(struct ubi_device *ubi, int pnum, int offset, int len);
+void ubi_dump_ec_hdr(const struct ubi_ec_hdr *ec_hdr);
+void ubi_dump_vid_hdr(const struct ubi_vid_hdr *vid_hdr);
+
+#include <linux/random.h>
+
+#define ubi_assert(expr)  do {                                               \
+	if (unlikely(!(expr))) {                                             \
+		pr_crit("UBI assert failed in %s at %u (pid %d)\n",          \
+		       __func__, __LINE__, current->pid);                    \
+		dump_stack();                                                \
+	}                                                                    \
+} while (0)
+
+#define ubi_dbg_print_hex_dump(l, ps, pt, r, g, b, len, a)                   \
+		print_hex_dump(l, ps, pt, r, g, b, len, a)
+
+#define ubi_dbg_msg(type, fmt, ...) \
+	pr_debug("UBI DBG " type " (pid %d): " fmt "\n", current->pid,       \
+		 ##__VA_ARGS__)
+
+/* General debugging messages */
+#define dbg_gen(fmt, ...) ubi_dbg_msg("gen", fmt, ##__VA_ARGS__)
+/* Messages from the eraseblock association sub-system */
+#define dbg_eba(fmt, ...) ubi_dbg_msg("eba", fmt, ##__VA_ARGS__)
+/* Messages from the wear-leveling sub-system */
+#define dbg_wl(fmt, ...)  ubi_dbg_msg("wl", fmt, ##__VA_ARGS__)
+/* Messages from the input/output sub-system */
+#define dbg_io(fmt, ...)  ubi_dbg_msg("io", fmt, ##__VA_ARGS__)
+/* Initialization and build messages */
+#define dbg_bld(fmt, ...) ubi_dbg_msg("bld", fmt, ##__VA_ARGS__)
+
+void ubi_dump_vol_info(const struct ubi_volume *vol);
+void ubi_dump_vtbl_record(const struct ubi_vtbl_record *r, int idx);
+void ubi_dump_av(const struct ubi_ainf_volume *av);
+void ubi_dump_aeb(const struct ubi_ainf_peb *aeb, int type);
+void ubi_dump_mkvol_req(const struct ubi_mkvol_req *req);
+int ubi_self_check_all_ff(struct ubi_device *ubi, int pnum, int offset,
+			  int len);
+int ubi_debugfs_init(void);
+void ubi_debugfs_exit(void);
+int ubi_debugfs_init_dev(struct ubi_device *ubi);
+void ubi_debugfs_exit_dev(struct ubi_device *ubi);
+
+/**
+ * The following function is a legacy implementation of UBI fault-injection
+ * hook. When using more powerful fault injection capabilities, the legacy
+ * fault injection interface should be retained.
+ */
+int ubi_dbg_power_cut(struct ubi_device *ubi, int caller);
+
+static inline int ubi_dbg_bitflip(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_bitflips)
+		return !get_random_u32_below(200);
+	return 0;
+}
+
+static inline int ubi_dbg_write_failure(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_io_failures)
+		return !get_random_u32_below(500);
+	return 0;
+}
+
+static inline int ubi_dbg_erase_failure(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_io_failures)
+		return !get_random_u32_below(400);
+	return 0;
+}
+
+/**
+ * MASK_XXX: Mask for emulate_failures in ubi_debug_info.The mask is used to
+ * precisely control the type and process of fault injection.
+ */
+/* Emulate a power cut when writing EC/VID header */
+#define MASK_POWER_CUT_EC			(1 << 0)
+#define MASK_POWER_CUT_VID			(1 << 1)
+/* Emulate a power cut when writing data*/
+#define MASK_POWER_CUT_DATA			(1 << 2)
+/* Emulate bit-flips */
+#define MASK_BITFLIPS				(1 << 3)
+/* Emulate ecc error */
+#define MASK_ECCERR				(1 << 4)
+/* Emulates -EIO during data read */
+#define MASK_READ_FAILURE			(1 << 5)
+#define MASK_READ_FAILURE_EC			(1 << 6)
+#define MASK_READ_FAILURE_VID			(1 << 7)
+/* Emulates -EIO during data write */
+#define MASK_WRITE_FAILURE			(1 << 8)
+/* Emulates -EIO during erase a PEB*/
+#define MASK_ERASE_FAILURE			(1 << 9)
+/* Return UBI_IO_FF when reading EC/VID header */
+#define MASK_IO_FF_EC				(1 << 10)
+#define MASK_IO_FF_VID				(1 << 11)
+/* Return UBI_IO_FF_BITFLIPS when reading EC/VID header */
+#define MASK_IO_FF_BITFLIPS_EC			(1 << 12)
+#define MASK_IO_FF_BITFLIPS_VID			(1 << 13)
+/* Return UBI_IO_BAD_HDR when reading EC/VID header */
+#define MASK_BAD_HDR_EC				(1 << 14)
+#define MASK_BAD_HDR_VID			(1 << 15)
+/* Return UBI_IO_BAD_HDR_EBADMSG when reading EC/VID header */
+#define MASK_BAD_HDR_EBADMSG_EC			(1 << 16)
+#define MASK_BAD_HDR_EBADMSG_VID		(1 << 17)
+
+#ifdef CONFIG_MTD_UBI_FAULT_INJECTION
+
+extern bool should_fail_eccerr(void);
+extern bool should_fail_bitflips(void);
+extern bool should_fail_read_failure(void);
+extern bool should_fail_write_failure(void);
+extern bool should_fail_erase_failure(void);
+extern bool should_fail_power_cut(void);
+extern bool should_fail_io_ff(void);
+extern bool should_fail_io_ff_bitflips(void);
+extern bool should_fail_bad_hdr(void);
+extern bool should_fail_bad_hdr_ebadmsg(void);
+
+static inline bool ubi_dbg_fail_bitflip(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_failures & MASK_BITFLIPS)
+		return should_fail_bitflips();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_write(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_failures & MASK_WRITE_FAILURE)
+		return should_fail_write_failure();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_erase(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_failures & MASK_ERASE_FAILURE)
+		return should_fail_erase_failure();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_power_cut(const struct ubi_device *ubi,
+					  unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_power_cut();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_read(const struct ubi_device *ubi,
+				     unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_read_failure();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_eccerr(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_failures & MASK_ECCERR)
+		return should_fail_eccerr();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_ff(const struct ubi_device *ubi,
+				   unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_io_ff();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_ff_bitflips(const struct ubi_device *ubi,
+					    unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_io_ff_bitflips();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_bad_hdr(const struct ubi_device *ubi,
+					 unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_bad_hdr();
+	return false;
+}
+
+static inline bool ubi_dbg_fail_bad_hdr_ebadmsg(const struct ubi_device *ubi,
+						 unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_bad_hdr_ebadmsg();
+	return false;
+}
+#else /* CONFIG_MTD_UBI_FAULT_INJECTION */
+
+#define ubi_dbg_fail_bitflip(u)             false
+#define ubi_dbg_fail_write(u)               false
+#define ubi_dbg_fail_erase(u)               false
+#define ubi_dbg_fail_power_cut(u, c)        false
+#define ubi_dbg_fail_read(u, c)             false
+#define ubi_dbg_fail_eccerr(u)              false
+#define ubi_dbg_fail_ff(u, c)               false
+#define ubi_dbg_fail_ff_bitflips(u, v)      false
+#define ubi_dbg_fail_bad_hdr(u, c)          false
+#define ubi_dbg_fail_bad_hdr_ebadmsg(u, c)  false
+
+#endif
+
+/**
+ * ubi_dbg_is_power_cut - if it is time to emulate power cut.
+ * @ubi: UBI device description object
+ *
+ * Returns true if power cut should be emulated, otherwise returns false.
+ */
+static inline bool ubi_dbg_is_power_cut(struct ubi_device *ubi,
+					unsigned int caller)
+{
+	if (ubi_dbg_power_cut(ubi, caller))
+		return true;
+	return ubi_dbg_fail_power_cut(ubi, caller);
+}
+
+/**
+ * ubi_dbg_is_bitflip - if it is time to emulate a bit-flip.
+ * @ubi: UBI device description object
+ *
+ * Returns true if a bit-flip should be emulated, otherwise returns false.
+ */
+static inline bool ubi_dbg_is_bitflip(const struct ubi_device *ubi)
+{
+	if (ubi_dbg_bitflip(ubi))
+		return true;
+	return ubi_dbg_fail_bitflip(ubi);
+}
+
+/**
+ * ubi_dbg_is_write_failure - if it is time to emulate a write failure.
+ * @ubi: UBI device description object
+ *
+ * Returns true if a write failure should be emulated, otherwise returns
+ * false.
+ */
+static inline bool ubi_dbg_is_write_failure(const struct ubi_device *ubi)
+{
+	if (ubi_dbg_write_failure(ubi))
+		return true;
+	return ubi_dbg_fail_write(ubi);
+}
+
+/**
+ * ubi_dbg_is_erase_failure - if its time to emulate an erase failure.
+ * @ubi: UBI device description object
+ *
+ * Returns true if an erase failure should be emulated, otherwise returns
+ * false.
+ */
+static inline bool ubi_dbg_is_erase_failure(const struct ubi_device *ubi)
+{
+	if (ubi_dbg_erase_failure(ubi))
+		return true;
+	return ubi_dbg_fail_erase(ubi);
+}
+
+/**
+ * ubi_dbg_is_eccerr - if it is time to emulate ECC error.
+ * @ubi: UBI device description object
+ *
+ * Returns true if a ECC error should be emulated, otherwise returns false.
+ */
+static inline bool ubi_dbg_is_eccerr(const struct ubi_device *ubi)
+{
+	return ubi_dbg_fail_eccerr(ubi);
+}
+
+/**
+ * ubi_dbg_is_read_failure - if it is time to emulate a read failure.
+ * @ubi: UBI device description object
+ *
+ * Returns true if a read failure should be emulated, otherwise returns
+ * false.
+ */
+static inline bool ubi_dbg_is_read_failure(const struct ubi_device *ubi,
+					   unsigned int caller)
+{
+	return ubi_dbg_fail_read(ubi, caller);
+}
+
+/**
+ * ubi_dbg_is_ff - if it is time to emulate that read region is only 0xFF.
+ * @ubi: UBI device description object
+ *
+ * Returns true if read region should be emulated 0xFF, otherwise
+ * returns false.
+ */
+static inline bool ubi_dbg_is_ff(const struct ubi_device *ubi,
+				 unsigned int caller)
+{
+	return ubi_dbg_fail_ff(ubi, caller);
+}
+
+/**
+ * ubi_dbg_is_ff_bitflips - if it is time to emulate that read region is only 0xFF
+ * with error reported by the MTD driver
+ *
+ * @ubi: UBI device description object
+ *
+ * Returns true if read region should be emulated 0xFF and error
+ * reported by the MTD driver, otherwise returns false.
+ */
+static inline bool ubi_dbg_is_ff_bitflips(const struct ubi_device *ubi,
+					  unsigned int caller)
+{
+	return ubi_dbg_fail_ff_bitflips(ubi, caller);
+}
+
+/**
+ * ubi_dbg_is_bad_hdr - if it is time to emulate a bad header
+ * @ubi: UBI device description object
+ *
+ * Returns true if a bad header error should be emulated, otherwise
+ * returns false.
+ */
+static inline bool ubi_dbg_is_bad_hdr(const struct ubi_device *ubi,
+				      unsigned int caller)
+{
+	return ubi_dbg_fail_bad_hdr(ubi, caller);
+}
+
+/**
+ * ubi_dbg_is_bad_hdr_ebadmsg - if it is time to emulate a bad header with
+ * ECC error.
+ *
+ * @ubi: UBI device description object
+ *
+ * Returns true if a bad header with ECC error should be emulated, otherwise
+ * returns false.
+ */
+static inline bool ubi_dbg_is_bad_hdr_ebadmsg(const struct ubi_device *ubi,
+					      unsigned int caller)
+{
+	return ubi_dbg_fail_bad_hdr_ebadmsg(ubi, caller);
+}
+
+/**
+ * ubi_dbg_is_bgt_disabled - if the background thread is disabled.
+ * @ubi: UBI device description object
+ *
+ * Returns non-zero if the UBI background thread is disabled for testing
+ * purposes.
+ */
+static inline int ubi_dbg_is_bgt_disabled(const struct ubi_device *ubi)
+{
+	return ubi->dbg.disable_bgt;
+}
+
+static inline int ubi_dbg_chk_io(const struct ubi_device *ubi)
+{
+	return ubi->dbg.chk_io;
+}
+
+static inline int ubi_dbg_chk_gen(const struct ubi_device *ubi)
+{
+	return ubi->dbg.chk_gen;
+}
+
+static inline int ubi_dbg_chk_fastmap(const struct ubi_device *ubi)
+{
+	return ubi->dbg.chk_fastmap;
+}
+
+static inline void ubi_enable_dbg_chk_fastmap(struct ubi_device *ubi)
+{
+	ubi->dbg.chk_fastmap = 1;
+}
+
+#endif /* !__UBI_DEBUG_H__ */