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 --- sound/firewire/lib.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 sound/firewire/lib.c (limited to 'sound/firewire/lib.c') diff --git a/sound/firewire/lib.c b/sound/firewire/lib.c new file mode 100644 index 000000000..654e1a605 --- /dev/null +++ b/sound/firewire/lib.c @@ -0,0 +1,72 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * miscellaneous helper functions + * + * Copyright (c) Clemens Ladisch + */ + +#include +#include +#include +#include +#include +#include "lib.h" + +#define ERROR_RETRY_DELAY_MS 20 + +/** + * snd_fw_transaction - send a request and wait for its completion + * @unit: the driver's unit on the target device + * @tcode: the transaction code + * @offset: the address in the target's address space + * @buffer: input/output data + * @length: length of @buffer + * @flags: use %FW_FIXED_GENERATION and add the generation value to attempt the + * request only in that generation; use %FW_QUIET to suppress error + * messages + * + * Submits an asynchronous request to the target device, and waits for the + * response. The node ID and the current generation are derived from @unit. + * On a bus reset or an error, the transaction is retried a few times. + * Returns zero on success, or a negative error code. + */ +int snd_fw_transaction(struct fw_unit *unit, int tcode, + u64 offset, void *buffer, size_t length, + unsigned int flags) +{ + struct fw_device *device = fw_parent_device(unit); + int generation, rcode, tries = 0; + + generation = flags & FW_GENERATION_MASK; + for (;;) { + if (!(flags & FW_FIXED_GENERATION)) { + generation = device->generation; + smp_rmb(); /* node_id vs. generation */ + } + rcode = fw_run_transaction(device->card, tcode, + device->node_id, generation, + device->max_speed, offset, + buffer, length); + + if (rcode == RCODE_COMPLETE) + return 0; + + if (rcode == RCODE_GENERATION && (flags & FW_FIXED_GENERATION)) + return -EAGAIN; + + if (rcode_is_permanent_error(rcode) || ++tries >= 3) { + if (!(flags & FW_QUIET)) + dev_err(&unit->device, + "transaction failed: %s\n", + fw_rcode_string(rcode)); + return -EIO; + } + + msleep(ERROR_RETRY_DELAY_MS); + } +} +EXPORT_SYMBOL(snd_fw_transaction); + +MODULE_DESCRIPTION("FireWire audio helper functions"); +MODULE_AUTHOR("Clemens Ladisch "); +MODULE_LICENSE("GPL"); -- cgit v1.3.1