From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug 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 Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- drivers/misc/cb710/debug.c | 115 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 drivers/misc/cb710/debug.c (limited to 'drivers/misc/cb710/debug.c') diff --git a/drivers/misc/cb710/debug.c b/drivers/misc/cb710/debug.c new file mode 100644 index 000000000..20d672edf --- /dev/null +++ b/drivers/misc/cb710/debug.c @@ -0,0 +1,115 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * cb710/debug.c + * + * Copyright by Michał Mirosław, 2008-2009 + */ +#include +#include +#include + +#define CB710_REG_COUNT 0x80 + +static const u16 allow[CB710_REG_COUNT/16] = { + 0xFFF0, 0xFFFF, 0xFFFF, 0xFFFF, + 0xFFF0, 0xFFFF, 0xFFFF, 0xFFFF, +}; +static const char *const prefix[ARRAY_SIZE(allow)] = { + "MMC", "MMC", "MMC", "MMC", + "MS?", "MS?", "SM?", "SM?" +}; + +static inline int allow_reg_read(unsigned block, unsigned offset, unsigned bits) +{ + unsigned mask = (1 << bits/8) - 1; + offset *= bits/8; + return ((allow[block] >> offset) & mask) == mask; +} + +#define CB710_READ_REGS_TEMPLATE(t) \ +static void cb710_read_regs_##t(void __iomem *iobase, \ + u##t *reg, unsigned select) \ +{ \ + unsigned i, j; \ + \ + for (i = 0; i < ARRAY_SIZE(allow); ++i, reg += 16/(t/8)) { \ + if (!(select & (1 << i))) \ + continue; \ + \ + for (j = 0; j < 0x10/(t/8); ++j) { \ + if (!allow_reg_read(i, j, t)) \ + continue; \ + reg[j] = ioread##t(iobase \ + + (i << 4) + (j * (t/8))); \ + } \ + } \ +} + +static const char cb710_regf_8[] = "%02X"; +static const char cb710_regf_16[] = "%04X"; +static const char cb710_regf_32[] = "%08X"; +static const char cb710_xes[] = "xxxxxxxx"; + +#define CB710_DUMP_REGS_TEMPLATE(t) \ +static void cb710_dump_regs_##t(struct device *dev, \ + const u##t *reg, unsigned select) \ +{ \ + const char *const xp = &cb710_xes[8 - t/4]; \ + const char *const format = cb710_regf_##t; \ + \ + char msg[100], *p; \ + unsigned i, j; \ + \ + for (i = 0; i < ARRAY_SIZE(allow); ++i, reg += 16/(t/8)) { \ + if (!(select & (1 << i))) \ + continue; \ + p = msg; \ + for (j = 0; j < 0x10/(t/8); ++j) { \ + *p++ = ' '; \ + if (j == 8/(t/8)) \ + *p++ = ' '; \ + if (allow_reg_read(i, j, t)) \ + p += sprintf(p, format, reg[j]); \ + else \ + p += sprintf(p, "%s", xp); \ + } \ + dev_dbg(dev, "%s 0x%02X %s\n", prefix[i], i << 4, msg); \ + } \ +} + +#define CB710_READ_AND_DUMP_REGS_TEMPLATE(t) \ +static void cb710_read_and_dump_regs_##t(struct cb710_chip *chip, \ + unsigned select) \ +{ \ + u##t regs[CB710_REG_COUNT/sizeof(u##t)]; \ + \ + memset(®s, 0, sizeof(regs)); \ + cb710_read_regs_##t(chip->iobase, regs, select); \ + cb710_dump_regs_##t(cb710_chip_dev(chip), regs, select); \ +} + +#define CB710_REG_ACCESS_TEMPLATES(t) \ + CB710_READ_REGS_TEMPLATE(t) \ + CB710_DUMP_REGS_TEMPLATE(t) \ + CB710_READ_AND_DUMP_REGS_TEMPLATE(t) + +CB710_REG_ACCESS_TEMPLATES(8) +CB710_REG_ACCESS_TEMPLATES(16) +CB710_REG_ACCESS_TEMPLATES(32) + +void cb710_dump_regs(struct cb710_chip *chip, unsigned select) +{ + if (!(select & CB710_DUMP_REGS_MASK)) + select = CB710_DUMP_REGS_ALL; + if (!(select & CB710_DUMP_ACCESS_MASK)) + select |= CB710_DUMP_ACCESS_8; + + if (select & CB710_DUMP_ACCESS_32) + cb710_read_and_dump_regs_32(chip, select); + if (select & CB710_DUMP_ACCESS_16) + cb710_read_and_dump_regs_16(chip, select); + if (select & CB710_DUMP_ACCESS_8) + cb710_read_and_dump_regs_8(chip, select); +} +EXPORT_SYMBOL_GPL(cb710_dump_regs); + -- cgit v1.3.1