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/cmp.h | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 sound/firewire/cmp.h (limited to 'sound/firewire/cmp.h') diff --git a/sound/firewire/cmp.h b/sound/firewire/cmp.h new file mode 100644 index 000000000..66fc08b74 --- /dev/null +++ b/sound/firewire/cmp.h @@ -0,0 +1,52 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef SOUND_FIREWIRE_CMP_H_INCLUDED +#define SOUND_FIREWIRE_CMP_H_INCLUDED + +#include +#include +#include "iso-resources.h" + +struct fw_unit; + +enum cmp_direction { + CMP_INPUT = 0, + CMP_OUTPUT, +}; + +/** + * struct cmp_connection - manages an isochronous connection to a device + * @speed: the connection's actual speed + * + * This structure manages (using CMP) an isochronous stream between the local + * computer and a device's input plug (iPCR) and output plug (oPCR). + * + * There is no corresponding oPCR created on the local computer, so it is not + * possible to overlay connections on top of this one. + */ +struct cmp_connection { + int speed; + /* private: */ + bool connected; + struct mutex mutex; + struct fw_iso_resources resources; + __be32 last_pcr_value; + unsigned int pcr_index; + unsigned int max_speed; + enum cmp_direction direction; +}; + +int cmp_connection_init(struct cmp_connection *connection, + struct fw_unit *unit, + enum cmp_direction direction, + unsigned int pcr_index); +int cmp_connection_check_used(struct cmp_connection *connection, bool *used); +void cmp_connection_destroy(struct cmp_connection *connection); + +int cmp_connection_reserve(struct cmp_connection *connection, + unsigned int max_payload); +void cmp_connection_release(struct cmp_connection *connection); + +int cmp_connection_establish(struct cmp_connection *connection); +void cmp_connection_break(struct cmp_connection *connection); + +#endif -- cgit v1.3.1