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/mips/tools/elf-entry.c | 103 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 arch/mips/tools/elf-entry.c (limited to 'arch/mips/tools/elf-entry.c') diff --git a/arch/mips/tools/elf-entry.c b/arch/mips/tools/elf-entry.c new file mode 100644 index 000000000..dbd14ff05 --- /dev/null +++ b/arch/mips/tools/elf-entry.c @@ -0,0 +1,103 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include + +#ifdef be32toh +/* If libc provides [bl]e{32,64}toh() then we'll use them */ +#elif BYTE_ORDER == LITTLE_ENDIAN +# define be32toh(x) bswap_32(x) +# define le32toh(x) (x) +# define be64toh(x) bswap_64(x) +# define le64toh(x) (x) +#elif BYTE_ORDER == BIG_ENDIAN +# define be32toh(x) (x) +# define le32toh(x) bswap_32(x) +# define be64toh(x) (x) +# define le64toh(x) bswap_64(x) +#endif + +__attribute__((noreturn)) +static void die(const char *msg) +{ + fputs(msg, stderr); + exit(EXIT_FAILURE); +} + +int main(int argc, const char *argv[]) +{ + uint64_t entry; + size_t nread; + FILE *file; + union { + Elf32_Ehdr ehdr32; + Elf64_Ehdr ehdr64; + } hdr; + + if (argc != 2) + die("Usage: elf-entry \n"); + + file = fopen(argv[1], "r"); + if (!file) { + perror("Unable to open input file"); + return EXIT_FAILURE; + } + + nread = fread(&hdr, 1, sizeof(hdr), file); + if (nread != sizeof(hdr)) { + perror("Unable to read input file"); + fclose(file); + return EXIT_FAILURE; + } + + if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) { + fclose(file); + die("Input is not an ELF\n"); + } + + switch (hdr.ehdr32.e_ident[EI_CLASS]) { + case ELFCLASS32: + switch (hdr.ehdr32.e_ident[EI_DATA]) { + case ELFDATA2LSB: + entry = le32toh(hdr.ehdr32.e_entry); + break; + case ELFDATA2MSB: + entry = be32toh(hdr.ehdr32.e_entry); + break; + default: + fclose(file); + die("Invalid ELF encoding\n"); + } + + /* Sign extend to form a canonical address */ + entry = (int64_t)(int32_t)entry; + break; + + case ELFCLASS64: + switch (hdr.ehdr32.e_ident[EI_DATA]) { + case ELFDATA2LSB: + entry = le64toh(hdr.ehdr64.e_entry); + break; + case ELFDATA2MSB: + entry = be64toh(hdr.ehdr64.e_entry); + break; + default: + fclose(file); + die("Invalid ELF encoding\n"); + } + break; + + default: + fclose(file); + die("Invalid ELF class\n"); + } + + printf("0x%016" PRIx64 "\n", entry); + fclose(file); + return EXIT_SUCCESS; +} -- cgit v1.3.1