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/scsi/sd_trace.h | 84 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 drivers/scsi/sd_trace.h (limited to 'drivers/scsi/sd_trace.h') diff --git a/drivers/scsi/sd_trace.h b/drivers/scsi/sd_trace.h new file mode 100644 index 000000000..cba3c0b82 --- /dev/null +++ b/drivers/scsi/sd_trace.h @@ -0,0 +1,84 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2022 Western Digital Corporation or its affiliates. + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM sd + +#undef TRACE_INCLUDE_FILE +#define TRACE_INCLUDE_FILE sd_trace + +#if !defined(_SD_TRACE_H) || defined(TRACE_HEADER_MULTI_READ) +#include +#include +#include + +TRACE_EVENT(scsi_prepare_zone_append, + + TP_PROTO(struct scsi_cmnd *cmnd, sector_t lba, + unsigned int wp_offset), + + TP_ARGS(cmnd, lba, wp_offset), + + TP_STRUCT__entry( + __field( unsigned int, host_no ) + __field( unsigned int, channel ) + __field( unsigned int, id ) + __field( unsigned int, lun ) + __field( sector_t, lba ) + __field( unsigned int, wp_offset ) + ), + + TP_fast_assign( + __entry->host_no = cmnd->device->host->host_no; + __entry->channel = cmnd->device->channel; + __entry->id = cmnd->device->id; + __entry->lun = cmnd->device->lun; + __entry->lba = lba; + __entry->wp_offset = wp_offset; + ), + + TP_printk("host_no=%u, channel=%u id=%u lun=%u lba=%llu wp_offset=%u", + __entry->host_no, __entry->channel, __entry->id, + __entry->lun, __entry->lba, __entry->wp_offset) +); + +TRACE_EVENT(scsi_zone_wp_update, + + TP_PROTO(struct scsi_cmnd *cmnd, sector_t rq_sector, + unsigned int wp_offset, unsigned int good_bytes), + + TP_ARGS(cmnd, rq_sector, wp_offset, good_bytes), + + TP_STRUCT__entry( + __field( unsigned int, host_no ) + __field( unsigned int, channel ) + __field( unsigned int, id ) + __field( unsigned int, lun ) + __field( sector_t, rq_sector ) + __field( unsigned int, wp_offset ) + __field( unsigned int, good_bytes ) + ), + + TP_fast_assign( + __entry->host_no = cmnd->device->host->host_no; + __entry->channel = cmnd->device->channel; + __entry->id = cmnd->device->id; + __entry->lun = cmnd->device->lun; + __entry->rq_sector = rq_sector; + __entry->wp_offset = wp_offset; + __entry->good_bytes = good_bytes; + ), + + TP_printk("host_no=%u, channel=%u id=%u lun=%u rq_sector=%llu" \ + " wp_offset=%u good_bytes=%u", + __entry->host_no, __entry->channel, __entry->id, + __entry->lun, __entry->rq_sector, __entry->wp_offset, + __entry->good_bytes) +); +#endif /* _SD_TRACE_H */ + +/* This part must be outside protection */ +#undef TRACE_INCLUDE_PATH +#define TRACE_INCLUDE_PATH ../../drivers/scsi +#include -- cgit v1.3.1