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 --- net/6lowpan/Makefile | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 net/6lowpan/Makefile (limited to 'net/6lowpan/Makefile') diff --git a/net/6lowpan/Makefile b/net/6lowpan/Makefile new file mode 100644 index 000000000..2247b96db --- /dev/null +++ b/net/6lowpan/Makefile @@ -0,0 +1,22 @@ +# SPDX-License-Identifier: GPL-2.0 +obj-$(CONFIG_6LOWPAN) += 6lowpan.o + +6lowpan-y := core.o iphc.o nhc.o ndisc.o +6lowpan-$(CONFIG_6LOWPAN_DEBUGFS) += debugfs.o + +#rfc6282 nhcs +obj-$(CONFIG_6LOWPAN_NHC_DEST) += nhc_dest.o +obj-$(CONFIG_6LOWPAN_NHC_FRAGMENT) += nhc_fragment.o +obj-$(CONFIG_6LOWPAN_NHC_HOP) += nhc_hop.o +obj-$(CONFIG_6LOWPAN_NHC_IPV6) += nhc_ipv6.o +obj-$(CONFIG_6LOWPAN_NHC_MOBILITY) += nhc_mobility.o +obj-$(CONFIG_6LOWPAN_NHC_ROUTING) += nhc_routing.o +obj-$(CONFIG_6LOWPAN_NHC_UDP) += nhc_udp.o + +#rfc7400 ghcs +obj-$(CONFIG_6LOWPAN_GHC_EXT_HDR_HOP) += nhc_ghc_ext_hop.o +obj-$(CONFIG_6LOWPAN_GHC_UDP) += nhc_ghc_udp.o +obj-$(CONFIG_6LOWPAN_GHC_ICMPV6) += nhc_ghc_icmpv6.o +obj-$(CONFIG_6LOWPAN_GHC_EXT_HDR_DEST) += nhc_ghc_ext_dest.o +obj-$(CONFIG_6LOWPAN_GHC_EXT_HDR_FRAG) += nhc_ghc_ext_frag.o +obj-$(CONFIG_6LOWPAN_GHC_EXT_HDR_ROUTE) += nhc_ghc_ext_route.o -- cgit v1.3.1