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 --- arch/xtensa/boot/lib/.gitignore | 4 ++ arch/xtensa/boot/lib/Makefile | 34 +++++++++++++++++ arch/xtensa/boot/lib/zmem.c | 81 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 119 insertions(+) create mode 100644 arch/xtensa/boot/lib/.gitignore create mode 100644 arch/xtensa/boot/lib/Makefile create mode 100644 arch/xtensa/boot/lib/zmem.c (limited to 'arch/xtensa/boot/lib') diff --git a/arch/xtensa/boot/lib/.gitignore b/arch/xtensa/boot/lib/.gitignore new file mode 100644 index 000000000..805a82492 --- /dev/null +++ b/arch/xtensa/boot/lib/.gitignore @@ -0,0 +1,4 @@ +# SPDX-License-Identifier: GPL-2.0-only +inffast.c +inflate.c +inftrees.c diff --git a/arch/xtensa/boot/lib/Makefile b/arch/xtensa/boot/lib/Makefile new file mode 100644 index 000000000..0378a22a0 --- /dev/null +++ b/arch/xtensa/boot/lib/Makefile @@ -0,0 +1,34 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Makefile for some libs needed by zImage. +# + +zlib := inffast.c inflate.c inftrees.c + +lib-y += $(zlib:.c=.o) zmem.o + +ccflags-y := -I $(srctree)/lib/zlib_inflate +ifdef CONFIG_FUNCTION_TRACER +CFLAGS_REMOVE_inflate.o = -pg +CFLAGS_REMOVE_zmem.o = -pg +CFLAGS_REMOVE_inftrees.o = -pg +CFLAGS_REMOVE_inffast.o = -pg +endif + +KASAN_SANITIZE := n +KCSAN_SANITIZE := n +KCOV_INSTRUMENT := n +GCOV_PROFILE := n + +CFLAGS_REMOVE_inflate.o += -fstack-protector -fstack-protector-strong +CFLAGS_REMOVE_zmem.o += -fstack-protector -fstack-protector-strong +CFLAGS_REMOVE_inftrees.o += -fstack-protector -fstack-protector-strong +CFLAGS_REMOVE_inffast.o += -fstack-protector -fstack-protector-strong + +quiet_cmd_copy_zlib = COPY $@ + cmd_copy_zlib = cat $< > $@ + +$(addprefix $(obj)/,$(zlib)): $(obj)/%: $(srctree)/lib/zlib_inflate/% + $(call cmd,copy_zlib) + +clean-files := $(zlib) diff --git a/arch/xtensa/boot/lib/zmem.c b/arch/xtensa/boot/lib/zmem.c new file mode 100644 index 000000000..b89189355 --- /dev/null +++ b/arch/xtensa/boot/lib/zmem.c @@ -0,0 +1,81 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +/* bits taken from ppc */ + +extern void *avail_ram, *end_avail; +void gunzip(void *dst, int dstlen, unsigned char *src, int *lenp); + +static void exit(void) +{ + for (;;); +} + +static void *zalloc(unsigned int size) +{ + void *p = avail_ram; + + size = (size + 7) & -8; + avail_ram += size; + if (avail_ram > end_avail) { + //puts("oops... out of memory\n"); + //pause(); + exit (); + } + return p; +} + +#define HEAD_CRC 2 +#define EXTRA_FIELD 4 +#define ORIG_NAME 8 +#define COMMENT 0x10 +#define RESERVED 0xe0 + +#define DEFLATED 8 + +void gunzip (void *dst, int dstlen, unsigned char *src, int *lenp) +{ + z_stream s; + int r, i, flags; + + /* skip header */ + i = 10; + flags = src[3]; + if (src[2] != DEFLATED || (flags & RESERVED) != 0) { + //puts("bad gzipped data\n"); + exit(); + } + if ((flags & EXTRA_FIELD) != 0) + i = 12 + src[10] + (src[11] << 8); + if ((flags & ORIG_NAME) != 0) + while (src[i++] != 0) + ; + if ((flags & COMMENT) != 0) + while (src[i++] != 0) + ; + if ((flags & HEAD_CRC) != 0) + i += 2; + if (i >= *lenp) { + //puts("gunzip: ran out of data in header\n"); + exit(); + } + + s.workspace = zalloc(zlib_inflate_workspacesize()); + r = zlib_inflateInit2(&s, -MAX_WBITS); + if (r != Z_OK) { + //puts("inflateInit2 returned "); puthex(r); puts("\n"); + exit(); + } + s.next_in = src + i; + s.avail_in = *lenp - i; + s.next_out = dst; + s.avail_out = dstlen; + r = zlib_inflate(&s, Z_FINISH); + if (r != Z_OK && r != Z_STREAM_END) { + //puts("inflate returned "); puthex(r); puts("\n"); + exit(); + } + *lenp = s.next_out - (unsigned char *) dst; + zlib_inflateEnd(&s); +} + -- cgit v1.3.1